Success! I tightened it by 3 turns, and that did 3 things. It made it hit 175kpa much sooner, 2997rpm instead of 3200, it mostly got rid of the fluctuations (now it fluctuates max peak to dip across the whole run 7kpa, which is much better than 23!), and it actually increased the wastegate value to 195 ish kpa. I wasn't necessarily looking to do that for a while, but it ran good once I raised the safety to 200 kpa, still very rich, still no ping, and now it pulls right up to 5000+, instead of dipping off with the fluctuations.
For the summer, the boost pressure should remain stable, but as winter approaches, you may notice that the boost pressure will increase. Keep an eye out for that!
On my car, I noticed the boost pressure (that was before I enabled closed-loop electronic boost control) in December was 10-15 kPa higher than in the summer.
For the summer, the boost pressure should remain stable, but as winter approaches, you may notice that the boost pressure will increase. Keep an eye out for that!
On my car, I noticed the boost pressure (that was before I enabled closed-loop electronic boost control) in December was 10-15 kPa higher than in the summer.
Interesting, I wonder why, I know when it's colder the air is denser and you'll get more power out of the same amount of air, but that shouldn't change the springs pressure, this is one of those things where you first look at it and it makes sense (cold air makes more power, more boost=more power), then my brain kicks up a gear and it doesn't make sense (a spring rated for x psi should be x psi no matter the temperature). Clearly I'm missing 3rd gear here, where it does make sense and have a logical reason, I'll look it up and see if I can find the answer instead of you typing out the scientific reason for this insignificant query haha.
Edit, I wonder if that is from the cold air getting heated up "more" than the warm air from compression (harder to compress denser air), even if it is still cooler, the temperature increase compared to warmer air might raise the pressure a bit, or it's from the denser air making more power, making more exhaust, spinning the turbo faster? Still I would think thata regulated x psi is still x psi no matter the temperature, oh well, that's enough for tonight!
[This message has been edited by 1985 Fiero GT (edited 07-01-2025).]
Interesting, I wonder why, I know when it's colder the air is denser and you'll get more power out of the same amount of air, but that shouldn't change the springs pressure, this is one of those things where you first look at it and it makes sense (cold air makes more power, more boost=more power), then my brain kicks up a gear and it doesn't make sense (a spring rated for x psi should be x psi no matter the temperature). Clearly I'm missing 3rd gear here, where it does make sense and have a logical reason, I'll look it up and see if I can find the answer instead of you typing out the scientific reason for this insignificant query haha.
Edit, I wonder if that is from the cold air getting heated up "more" than the warm air from compression (harder to compress denser air), even if it is still cooler, the temperature increase compared to warmer air might raise the pressure a bit, or it's from the denser air making more power, making more exhaust, spinning the turbo faster? Still I would think thata regulated x psi is still x psi no matter the temperature, oh well, that's enough for tonight!
As they say... I'm not a biologist (haha), but I'd imagine that the temperature changes would in fact affect the metal in the springs... though at temperature they should operate the same. But the denser air would likely mean more pressure... as you say, it would be harder to compress the denser air.
Originally posted by 82-T/A [At Work]: As they say... I'm not a biologist (haha), but I'd imagine that the temperature changes would in fact affect the metal in the springs... though at temperature they should operate the same. But the denser air would likely mean more pressure... as you say, it would be harder to compress the denser air.
If that were the case and summer to fall temps would change the rating of the spring, then you'd get insane fluctuations at other times (cold start would be huge boost, then as the turbo heats up it would reduce a lot, the wastegate gets baked being so close to the turbo), anyhow, I don't fully know haha.
So I'm at 640 ish kms now, no real problems at all. I had some impressive oil leaks, from a damaged axle seal and a disintegrated o ring on the dipstick tube, I replaced that and those leaks are no more. I think I have a little bit coming from the front main seal (tiny amount at the moment, so little it's hard to pinpoint, might just be residual from the big leaks). I did an oil change at 500kms, oil was still nice and clean, no sludge, metal or anything. I also had the oil pressure sender go out, I have it running the o2 sensor, and the switch wasn't the most reliable, then just stopped working. New oil pressure sender works perfect on the switch front, but seems to read lower than the last one (have a video of the last one reading 50 psi @ 1700 rpm @ 63°f, This morning the cold start number was 37.5 psi @ 1700 rpm @ 71°f) and the new sender idles at 20psi @ 975 rpm fully warmed up, 1 tick off the red. This is with new 10w40 conventional. Does that sound normal to you guys? This engine's spec is 15 psi @ 1100 rpm, so it's still above spec, but seeing it go down a bit from the old sender, and go down even more from my 2.8s sender (it almost never left 80 psi, the sender was definitely not working at all), just caught my attention. Is the new sender reading low, or the last sender reading high, or a little of both? What does the White Bug idle at warm? I'm positive that the oil pressure change is just the sender's fault, and not bearings or anything, because the oil pressure drop happened all at once with the sensor change, and hasn't dropped any more since, and I've already driven farther since that sender change than the bearings even lasted on the first iteration of this engine
I also got a tiny bit of pinging today when it was hottest, and that made me think back to the last couple times I've had that, I thought I fixed it by re timing the distributor, or enrichening the mixture, and after I had done those things the ping was gone. Then I realized that I had gotten gas at a different station than normal immediately after the first time, and the other time I didn't test it again immediately (no fun driving with the windows up trying to hear pinging when it's so hot, so I waited until it was cooler). So I looked at the octane I was running, it was the highest at the station I usually go to, which was only 90, no ethanol, the time I filled up at a different station and didn't have any pinging, I got 91 octane, so I think I was not using fuel with enough octane, as I've had encountered slight pinging maybe 3 or 4 times, usually at the hottest part of the day. I found out Shell sells 93 octane, so I topped off my tank with that, didn't have any pinging on the way home (it was cooler than this afternoon, but still windows down temperature). I'll have to see on the way home from church tomorrow if the splash of 93 fixed that, and if not then I'll have to burn through the rest of the tank and fully try 93 octane and see if that will do it. It won't cost any extra to use 93 octane, turns out in Maine 90 octane is ethanol free and more expensive, so with regular 5-10% ethanol 93 octane I'm only paying $1.40 cad/liter. PMBrunelle, what octane do you use? What boost was that good to before you had to use the water injection? or did you not wait to encounter ping before implementing the water injection?
[This message has been edited by 1985 Fiero GT (edited 07-06-2025).]
20 psi should be enough at idle. Shouldn’t your oil pressure gauge read in kPa rather than psi if it is a Canadian Z49 Fiero? I think that mine idles around 35 psi, but I don’t remember exactly.
How did you find TDC when you marked your harmonic balancer? Did you use a piston stop? Is your ignition timing what you think it is?
I never encountered knock with my car. I started running water injection more as a preventive measure.
I’m running 91 octane pump gas, which is available anywhere. Nowadays in Québec the pump gas has 10% ethanol.
As you are aware, the AKI of fuel is the average of the RON and MON, which represent two different test conditions for octane. So, depending on the running parameters of the test engine, you get a different octane measurement.
Some experienced tuners (not me, I saw this on Reddit) have reported that in a turbo engine, E10 has more knock resistance than pure gasoline with the same AKI. RON and MON test conditions are perhaps not fully applicable to turbo engines.
[This message has been edited by pmbrunelle (edited 07-06-2025).]
20 psi should be enough at idle. Shouldn’t your oil pressure gauge read in kPa rather than psi if it is a Canadian Z49 Fiero? I think that mine idles around 35 psi, but I don’t remember exactly.
How did you find TDC when you marked your harmonic balancer? Did you use a piston stop? Is your ignition timing what you think it is?
I never encountered knock with my car. I started running water injection more as a preventive measure.
I’m running 91 octane pump gas, which is available anywhere. Nowadays in Québec the pump gas has 10% ethanol.
As you are aware, the AKI of fuel is the average of the RON and MON, which represent two different test conditions for octane. So, depending on the running parameters of the test engine, you get a different octane measurement.
Some experienced tuners (not me, I saw this on Reddit) have reported that in a turbo engine, E10 has more knock resistance than pure gasoline with the same AKI. RON and MON test conditions are perhaps not fully applicable to turbo engines.
Ok, yes it's in kpa, I was converting to psi because most people on the forum are Americans, I forgot that you would also be in kpa, for the combined tach/oil gauge, it is divided into 4 sections of 20 psi, each with 4 ticks being 5 psi, with the first white tick off the red being 20, 275 is 40, 550 is 80
The first time I simply copied from the old balancer, the second time I used a screwdriver down the #1 spark plug hole and first rotated the engine by hand clockwise until I felt it wasn't going up or down, then went past and came back to TDC counter clockwise and did the same thing. I made note of the location and did that once more in each direction, and all results were within about 2* of each other, so I timed it to that new number, which was several (9 if I remember) degrees retarded from what I had it at to start with. I also reduced the spark tables several degrees from what you had so this engine would have no excuse to have any issues (which is probably why it didn't have any issues with the balancer being 9* off), so if my balancer is currently wrong, it would be wrong in the retarded direction unless my old balancer was more than 9 degrees more advanced (considering it ran the 2.8 fine at 12* timing (total of 11* more than "stock"), I doubt it was any more than that, and if it ends up a little retarded, that's fine.
Makes sense, so with the heat and compression of a turbo, ethanol free 90 would have been significantly worse than even just e10 91, well once I run this tank through and I get a really hot day with 93 I'll test again and hopefully I don't get any noises. And this pinging, I haven't really described it, it isn't metallic or deep, or really fast, it is just a little rattle, infrequent enough that I can discern each one, but to fast to count when it happens, so it isn't happening on every cylinder or even every combustion on one cylinder, I don't feel it in the way the engine runs, and it's pretty quiet, so it's definitely extremely mild, but enough to want to figure it out. If 93 solves this, then I'll try a tank of 91 octane, see what the lowest I can go is before it happens again, so I know what I can use gas wise if I'm somewhere else.
Rodney had one last set of poly transmission mounts, so I ordered those, I'm going to order a poly engine mount from Fierospace.com, as Rodney's out of those, I also ordered Rodney's adjustable solid dog bone, because it was cheaper than his adjustable poly one, that should definitely tighten down the drivetrain movement, as there's definitely quite a bit at the moment, and I've heard bad things about the replacement rubber mounts that I have now.
More driving today, now at 3/4 tank 93 octane, 1/4 tank 90 octane, still had the ping, and this evening I actually hit boost cut again (was pretty cold and rainy out, so that confirmed that temperature effects boost, somehow haha).
I was looking at the spark timing I was using (from an older tune from the White Bug), and looking at the spark timing other people have used (some other msqs from the megasquirt forum, and the tables from the book "high performance Fieros"), and I see that under boost (specifically 200 kpa), the timing was between 10 and 18 degrees more advanced (in the book, they use a 3.4l, iron head, and the timing is 0 across all rpms @ 200 kpa, whereas I had up to 18*, others on the megasquirt forum (Ericjon262 was one I saw I think) were in the 8* range, in my initial setup I had lowered the timing 4 degrees from what it was (so up to 14* at 200 kpa, seemingly without effect), so now I've put in the table from the book (above 100 kpa, no point messing with the vacuum timing that I know works fine), tomorrow I'll see if that finally gets rid of my pinging, if so I'll wait for a good hot day to increase it incrementally until I get the ping back, then know what the limit is. Afr is at 10-11 across the rpms at 200 kpa, so I know I'm not going lean.
It is knock, and not the “spark blowout”? “Spark blowout” is a misnomer as it designates the failure to initiate a spark when the cylinder pressure is too high. Reducing the spark plug gap is one way to facilitate spark formation.
Removing and inspecting the spark plugs may give you some hints about how the engine is running.
Is your intercooler working with water/antifreeze circulating?
Excessive ignition timing retard is not necessarily "safe", because the exhaust gas does not fully expand (and hence cool) inside the cylinder. So the exhaust valves and exhaust manifolds are subjected to high exhaust gas temperature.
You may need to reduce the boost pressure if you have a knock problem that you cannot otherwise solve.
There are aftermarket wastegate actuators with replaceable springs sets which you could use to fine-tune your boost pressure. I have one from Tial. Turbosmart sells another one.
It is knock, and not the “spark blowout”? “Spark blowout” is a misnomer as it designates the failure to initiate a spark when the cylinder pressure is too high. Reducing the spark plug gap is one way to facilitate spark formation.
Removing and inspecting the spark plugs may give you some hints about how the engine is running.
Is your intercooler working with water/antifreeze circulating?
Excessive ignition timing retard is not necessarily "safe", because the exhaust gas does not fully expand (and hence cool) inside the cylinder. So the exhaust valves and exhaust manifolds are subjected to high exhaust gas temperature.
You may need to reduce the boost pressure if you have a knock problem that you cannot otherwise solve.
There are aftermarket wastegate actuators with replaceable springs sets which you could use to fine-tune your boost pressure. I have one from Tial. Turbosmart sells another one.
I don't think it is spark blow out because I've had the same symptoms intermittently everywhere from 175 kpa to 195kpa after the wastegate adjustment, but always around the same rpms. It was a hot day today so I did some driving at 0*, no symptoms at all, then I split the difference to what I had, so now it peaks at 7* at 200kpa, and I had no symptoms again. By that point I was overheating (can't hear the knock with the windows down or fan turned up and no AC) so I didn't test any further. I can check some plugs tomorrow, I had them gapped to 0.040", with an MSD coil, fresh wires and distributor, what should I look for on them/what should they be gapped at?
To the best of my knowledge the intercooler is fully functional, whenever I stop driving, it is cool/cold (compared to the rest of the engine bay) to the touch, and there is a noticeable temperature difference between the silicone air tubes going into it and the ones going out of it, I also see the iat sensor (installed in the water line) go up a few degrees when doing an acceleration, then return to ambient or very close.
My thoughts are that my setup is different enough from yours to significantly impact correct spark timing, for example using the distributor vs the 7x wheel, putting more play into the measurement, and of course the little bit of uncertainty around the balancer marks. Hopefully my knock does not return, I'll look at some spark plugs tomorrow.
Would minor spark "blow out" or any other things give me those symptoms, a very small rattle like sound, no loss in power or other change in the way the engine is running or feels. I almost feel it is something totally different, maybe something related to drivetrain movement, or something, just because of how small and quiet it is, and how random yet reoccurring it has been.
Checked my spark plugs, a little sooty, but the insulator and tip are a lighter gray. No buildup, erosion, slime, etc.
Plus 1-6
All of them looked very similar in person, my phone camera is pretty bad, number 1 and 3 are the closest to how they look in person the other ones showed up darker on camera than they are.
Spark gap was at 0.045", with one at 0.050". I lowered them all to 0.040" to be on the safe side, and then did a little more driving, with no ping/knock.
I ran 0.030” spark plug gaps for a long time, but in more recent tests in the 210-215 kPa range, the engine misfired, so I backed it down to 200 kPa. In my next steps, I think I will try 0.025” gaps and then see if I can increase the boost again.
A misfire will be accompanied by a power loss. Knock will not necessarily cause a power reduction.
I don’t see anything horrible on the spark plugs, but obviously the idle/cruise mixture seems like it’s still too rich. I guess it’s on your to-do list.
Are there any altitude changes with your driving? The greater the altitude, the greater will be the pressure ratio (and therefore temperature rise) of the compressor. Hotter air will be more knock-prone.
I ran 0.030” spark plug gaps for a long time, but in more recent tests in the 210-215 kPa range, the engine misfired, so I backed it down to 200 kPa. In my next steps, I think I will try 0.025” gaps and then see if I can increase the boost again.
A misfire will be accompanied by a power loss. Knock will not necessarily cause a power reduction.
I don’t see anything horrible on the spark plugs, but obviously the idle/cruise mixture seems like it’s still too rich. I guess it’s on your to-do list.
Are there any altitude changes with your driving? The greater the altitude, the greater will be the pressure ratio (and therefore temperature rise) of the compressor. Hotter air will be more knock-prone.
Ok, interesting, none of this has ever had an accompanying power loss, the only symptom is the sound.
Yes, I wanted to figure out this sound before making anything leaner, but I will work on that.
There are lots of small altitude changes as I live in the Appalachians (basically this whole area is just a bunch of large hills, so there are dozens of changes in a drive, none super big though that I know of), that could certainly be a factor to, my ECM has a barometer built in although I don't think I have any of those features tuned or turned on yet.
I did a little more driving in 1st Gear, and I think it is fairly similar to the 4 speed in terms of bucking, maybe less, definitely not more,
Ok, now that bothersome ping seems to be gone (I raised the advance to up to 10* at 200 kpa now, no ping has returned), I felt confident enough to take it to some higher rpms, up till now I've done 1000 kms shifting at 4500 or below. I did a couple of accelerations up as high as it would go, which immediately showed something wrong, as it was like a soft limit at between 5000-5300 rpm, boost remains at 195kpa, there's no breaking up, no extra noise, no detonation, it just rapidly falls on its face between 4500 and 5000, and tops out at 5000-5300, when the throttle is being applied. If I stay at 30-40% TPS (like 110 kpa), it pulls smoothly at that amount up past 5500 (highest I've gone), but as soon as the throttle is floored or increased enough to go into boost (spooled from 116-140kpa, with increase in throttle, and a slight decrease in rpms), it falls on its face, release throttle a good bit, it goes as normal. I removed my plugs and regapped to 0.030", no change.
So I'm thinking this is exhaust back pressure? If it were spark blow out then I don't think it would feel/sound so smooth, it is still firing normally on all cylinders, but somehow that isn't translating into power. Same reason I don't believe it to be detonation. I don't think it's valve float because it drives fine at no boost with little throttle, and just using the throttle I can go from normal accel no boost to full boost with no acceleration at all. Literally the only symptom is that it falls on its face at 5000 rpm under boost.
I can try disconnecting the downpipe from the cat flange, and just have the 2 feet of exhaust coming down from the turbo and see if the restriction is post turbo.
Boost applies pressure to the intake valves and tries to open them. I suspect you are seeing valve float and need stiffer springs.
Without boost you are able to rev a little higher because boost is no longer helping to push the valve open.
But then wouldn't that same level of boost be opening them at lower rpms? I hit 195 kpa at 3300 rpm and it stays there all the way up. Also wouldn't the valve train rapidly get very noisy if the intake valves are being held open, then the lifters and pushrods and rockers would just be flapping around. At 5000 rpm, transitioning between low throttle and higher throttle, there's no change in valve train noise, no additional noises at all other than the turbo, but the engine falls on its face. Also at that rpm the bog isn't just happening at 195 kpa, it's happening with as little as 50% throttle and 150 kpa when I quickly increase the throttle pedal while already at those speeds.
Originally posted by 1985 Fiero GT: So I'm thinking this is exhaust back pressure? If it were spark blow out then I don't think it would feel/sound so smooth
Misfires feel like hitting the rev limiter... the rev limiter is a series of "desired" misfires.
I think that valve float could happen smoothly without any bad sounds.
Valve float happens when the valve spring is not stiff enough to apply enough force to keep the lifter in contact with the lobe as it descends. The faster the camshaft is spinning, the stiffer the valve spring needs to be to maintain contact.
Boost pressure on the intake valve counteracts the valve spring force.
It is a combination of boost and RPM that can cause float.
You have redone heads from 82 T/A [At Work], right?
Did he use stiffer springs than stock 2.8? Stiffer than for stock 3400 (as you have a 3400 camshaft)?
I think that valve float could happen smoothly without any bad sounds.
Valve float happens when the valve spring is not stiff enough to apply enough force to keep the lifter in contact with the lobe as it descends. The faster the camshaft is spinning, the stiffer the valve spring needs to be to maintain contact.
Boost pressure on the intake valve counteracts the valve spring force.
It is a combination of boost and RPM that can cause float.
You have redone heads from 82 T/A [At Work], right?
Did he use stiffer springs than stock 2.8? Stiffer than for stock 3400 (as you have a 3400 camshaft)?
It's not like a full spark cut limiter, no misfires or anything, just a seemingly smooth Rev limiter.
Yes these are the rebuilt heads from 82 T/A, rebuilt as a part of a Camaro 3.4l, I don't know specifics on the springs other than that they were new, and gm specs are 79 pounds closed pressure, gm specs for the 3400 springs are 74 pounds closed. Open specs are 230lbs@11.2mm compression from closed spec for the 3400 and 185lbs@10.4mm compression for the 3.4. I don't know if the open pressures will be similar with the 3400 cam pushing further on the 3.4 springs, I'm using the correct rockers (1.6) for it, so it should have a profile that matches an original aluminum head 3400, just with iron heads and their valves.
Originally posted by 1985 Fiero GT: I don't know specifics on the springs other than that they were new, and gm specs are 79 pounds closed pressure, gm specs for the 3400 springs are 74 pounds closed.
14.7 lbs boost on a 1.5" valve will add about 25 lbs resisting the closing of the valve (excluding the reduction due to valve stem). So when you only have 74 lbs spring force closed and the air trying to keep the valve open is pushing back at 25lbs, then you only have 50 lbs to close the valve and prevent valve float. This will lower the RPM that valve float will happen. On a non-interference engine, valve float just feels like power leveling offs.
For reference, the closed pressure on my springs (and different engine family) is about 155 lbs. So far they have been float free with 0.600" lift @ 7300 rpm and 8 psi on a 2" valve.
14.7 lbs boost on a 1.5" valve will add about 25 lbs resisting the closing of the valve (excluding the reduction due to valve stem). So when you only have 74 lbs spring force closed and the air trying to keep the valve open is pushing back at 25lbs, then you only have 50 lbs to close the valve and prevent valve float. This will lower the RPM that valve float will happen. On a non-interference engine, valve float just feels like power leveling offs.
For reference, the closed pressure on my springs (and different engine family) is about 155 lbs. So far they have been float free with 0.600" lift @ 7300 rpm and 8 psi on a 2" valve.
Ok, interesting, how bad is that for the camshaft and lifters?
Originally posted by 1985 Fiero GT: Ok, interesting, how bad is that for the camshaft and lifters?
It isn't great, but not immediately catastrophic on a non-interference engine. Now on an interference engine, it can be catastrophic with bent valves and holes in pistons.
It isn't great, but not immediately catastrophic on a non-interference engine. Now on an interference engine, it can be catastrophic with bent valves and holes in pistons.
Ok, well, I know what I'll be doing soon, I'll maybe do my t-tops while I change the valve springs, maybe I'll wait till winter though, I want to get to an autocross mid August.
With the right tools, you can replace the valve springs in the car w/o dropping the engine.
DId some work on a SBC swap once and the customer wanted to switch from 1.5 to 1.6 roller rockers (and these were steel). Just doing that cause it to valve float at 5800 rpm when it used to pull to 6500+ and it was down about 30-40 hp from what it should have made on the dyno. Swapped to a stiffer set of springs and it pulled strong to 6800 rpm.
With the right tools, you can replace the valve springs in the car w/o dropping the engine.
DId some work on a SBC swap once and the customer wanted to switch from 1.5 to 1.6 roller rockers (and these were steel). Just doing that cause it to valve float at 5800 rpm when it used to pull to 6500+ and it was down about 30-40 hp from what it should have made on the dyno. Swapped to a stiffer set of springs and it pulled strong to 6800 rpm.
Yes, I don't intend to drop the engine, I'll do it from the top only, I'll save the t tops for later, order parts tonight and start working on that as soon as I get the parts, should be back together for autocross hopefully.
The Fiero store performance valve springs should be good right?
105lbs closed, 296lbs @ 0.5" open (3400 cam with 1.6 rockers should be 0.44" lift, so should be about 271lbs open @0.44") Current is 79lbs closed, 193 open (calculated spring rate from original 3.4, then recalculated for the higher lift 3400 cam/rockers). So with 25lbs of air pressure on the valve, it should be about the same closed pressure as na, and 50 lbs more fully open, that sound about right?
Originally posted by 1985 Fiero GT: The Fiero store performance valve springs should be good right?
105lbs closed, 296lbs @ 0.5" open
The White Bug has valve springs in that range.
Ideally, you should identify what you have now, because if your heads already have similar performance valve springs, then there will be no improvement.
Of course, check for coil bind with new springs...
Stiffer springs and higher operating RPMs will be harder on the rocker arm ball pivots, so you should probably check them regularly for bluing / oil coking around the pivot socket area soon after installing stiffer valve springs.
You can likely check this by looking through the oil fill cap with a flashlight.
Ideally, you should identify what you have now, because if your heads already have similar performance valve springs, then there will be no improvement.
Of course, check for coil bind with new springs...
Stiffer springs and higher operating RPMs will be harder on the rocker arm ball pivots, so you should probably check them regularly for bluing / oil coking around the pivot socket area soon after installing stiffer valve springs.
You can likely check this by looking through the oil fill cap with a flashlight.
Ok, the heads were standard rebuilt crate engine stuff from a 3.4 Camaro engine, the numbers I posted above were gm specs for that engine/springs, and are roughly around the same as the stock 2.8 springs, but definitely not performance in any way, 82 T/As crate engine was a stock remanufactured engine, so while they were new, they wouldn't have been performance.
I'm doing some measuring and calculating in regards to avoiding coil bind when I do this.
3400 cam is 0.2727" lift intake and exhaust apparently, going through 1.6 rockers (as factory on a 3400) that ends up being 0.4363" of lift at the valve.
GM specced install height for the iron head 3.4 valve springs is 1.61", for the 2.8 it's 1.575". I tried my best to measure through the oil fill cap and got slightly over 1.6 but less than 1.65".
All the "performance springs" are specced at 1.7" install height, and I can't find out what springs the Fiero store uses, and The specs don't perfectly line up with anything in major brands catalogs. Some people have said they are comp cams and some people say Crane. The closest I could find from either manufacturer both coil bind at 1.15".
So with the 3400 cam and associated 1.6 rockers, 3.4 iron head spec install height, I would be 0.0237" from coil bind, that's not enough.
I looked at the White Bug thread, the install height measurement after the last broken rockers was 1.609", which is to spec, and I see that the Crower springs used have a coil bind height of 1.13", with those springs I'd be 0.0437" from coil bind, still below the general guideline of 0.060".
I think I'll get a set of 0.050 offset valve keepers and the Fiero store springs, which should be 0.0737"-0.0937" from coil bind, depending whether they are comp/crane or perhaps Crower springs. I'll accurately measure the heights when I have the valve covers off, and go from there.
Did a compression test on all cylinders when I removed the spark plugs to gap them smaller, I cranked it 5 pulses, and recorded the gauge while I did that.
So I have one cylinder that's a little low (it had been lower, 100 psi, but I re-tested it after all the others, and it had improved to 110), one that's a little high (that is the one I removed the piston to check the ring gaps, I had oiled it up to put it back in) remember this is a junkyard 3400 that has run maybe 2 minutes in the last several years or more, and was stone cold, so perhaps cyl 1 will improve with time, I will check it again after it has gotten back on the road. Test was done with no upper intake, battery on charger, no fuel or spark, all plugs removed the entire test.
Working on the valve springs today, I did another compression test, this one was much much better: Cyl 1:141 Cyl 2:142 Cyl 3:142 Cyl 4:144 Cyl 5:142 Cyl 6:140 That's the difference 1200kms of running vs 30 seconds of cranking after years of being in a junkyard makes, now I have a 4 psi max difference, instead of 40psi! Overall all the numbers are averaging over 10psi higher.
Valve springs are in, along with Howard's cams 0.050 offset valve keepers, measured install height on intake valve is 1.695", it's 0.030 less on the exhaust because of the extra piece that goes around the top of the spring. Should be 0.10" before coil bind on the intake and 0.070" on the exhaust.
Tomorrow I'll finish getting the intake back together and hopefully be able to get it back on the road!
Valve springs changed a while ago, now it revs much more freely.
I got some touren wheels, 16x7 42mm front, 17x7.5 42mm rear, and Firestone Firehawk Indy 500 tires, 205/55r16 front, and 235/50r17 rear. I wanted a significant outer diameter increase for the rear, as I wanted a lower cruise rpm, now 2400@110 km/h. I might have wanted wider rear tires, but they aren't available with enough sidewall for the bad roads here, and a large enough diameter to put the rpms where I want. The only matching rims front and back with different widths I could find were only half an inch, in my budget, that's why I don't have wider tires on the rear, the tires match the rims pretty well and have a good sidewall and diameter.
I put coil overs on the rear, 10" 250lb eibach springs, and did my best to calculate flat ride and shift the balance slightly towards the rear because of my rear sway bar (it was slightly more oversteer than I could want) and to match the rear to the front (Camaro springs cut down) but some calculation was wrong as I didn't have to cut the springs down as much as I expected (first cut was supposed to be a safe, tall cut, instead was basically right on my intended final result). Anyhow maybe it isn't matched as well as I thought, but it rides great, basically feels like it did, but just a bit stiffer. Also lowered the front bump stops, jacked up the suspension with no spring to make sure the wheel clears the wheel well and lowered the bump stop to get it closer, ended up being about 5/8" shorter.
With the wheels being spaced farther inwards, and 205 front instead of 215, steering effort was greatly reduced, like by a lot, I'm also experimenting with removing the steering shock, now that the wheels have higher offset, bumps don't act on the steering as much, and I like it, slightly more movement of the wheel going over bumps than with the shock, but much less than my dad's stock Fiero with seemingly a blown steering shock. Perfectly drivable and enjoyable, and makes inputs feel even lighter and quicker.
Stock (but great shape/fresh premium pads) brakes feel slightly less effective with the larger diameters, but still good, and I don't mean less effective in total stopping power, as the old tires locked up before the brakes topped out, but everything requires a little more brake input, but I can still get the tires to squeal/lock if I want to.
I have an autocross tomorrow, so I'll see how everything is balanced driving on a course, I know on the road everything feels great, but I haven't had a chance to take some corners to feel the front/rear traction balance much yet.
I did the autocross, my Fiero feels much more balanced now than before with stock suspension and a rear swaybar. The tires grip very well, and the engine and transmission were great. I myself tend to get lost on autocross courses, especially the huge one here at the closed Loring AFB, so my times weren't very good compared to others in my class, but they are much better than they were 2 years ago. upon exiting the autocross area, there's a closed 1.5 mile taxiway/runway you drive down, and I opened up the throttle, I hit 223 km/h @ 75% tps, 170 kpa, and about 4800rpm (first time going that fast, so I was easing into it, that is I was until the headlight doors popped up, then I slowed down. Also to verify the calculated ecm datalog speed, I calculated the speed based on rpm, gearing, and tire size). Definitely had much more to go, but that was enough for me!
How is it at 223 km/h? Does the front end feel light in the steering?
I see you still have the hardtop. You are autocrossing the car, and handling does seem to be important. Are you sure that the T-top modification is a good idea? It is going to be a weight adder, and a strength/stiffness reducer.
How is it at 223 km/h? Does the front end feel light in the steering?
I see you still have the hardtop. You are autocrossing the car, and handling does seem to be important. Are you sure that the T-top modification is a good idea? It is going to be a weight adder, and a strength/stiffness reducer.
How do T-top Fieros drive?
It is so far!
Planted, solid, almost serene. It feels no different going straight at 220 than straight at 110, there were no curves or bumps, so I can't speak about that, as it didn't need hardly any steering input, I mean I felt comfortable enough to take a hand off and wind my windows up at about 160 (it was getting a little too hard on the ears haha), it certainly feels much much better at those speeds than my dad's Fiero at just 80, it has a lot of bad bushings and a bad alignment.
I've autocrossed only twice now, I've never driven a t top Fiero, so I don't know how that will effect stiffness, and while handling is indeed important, my Fiero is not so much a sports car in your definition. I like the GT designation, comfortable for Highway driving, good, not necessarily best handling, a fun amount of power, but perfectly drivable and smooth when required, a nice combination of luxury/performance. My Fiero doesn't have AC, and I like driving with a lot of airflow, and being in more of a "fishbowl" with lots of glass or open air all around me, so for the looks inside and out, and the added airflow, it will be worth less chassis stiffness. Realistically with these tires and springs/sway bars/bushings I have, it handles almost a little too good, my 140lbs is losing traction in the seat before the tires! If this were a track car or more sport over touring oriented, I would likely have racing seats or something with better side support, but for me the Mr Mike's seats are staying, no question about that haha. I also don't think the weight will be increased much, the whole roof panel can't weigh more than 25 pounds extra, and the sunroof I have already is pretty comparable to the 2 t top panels, they almost seem to be a thinner glass, I don't know.
If I get a chance to go that fast again, I'll make sure to pop the hood first, to relieve some of that air pressure. Speaking about performance vs comfort, I don't want to do a hood vent, because then my only source of air with a closed cabin would be heated up by the air from under the hood, I enjoy how cool the air comes in compared to front engined cars, if I had AC that wouldn't matter either, but I don't so for me maybe having slightly cooler vent air is more important than maybe having less pressure buildup over 200km/h.
My select cable is freezing up when the engine is cold, it is the one nearest the exhaust, so I believe that it has somewhat melted, when hot, it is still sticky but not frozen. So far that has not impacted driveability to much, I park it in the gear I'll next need, by the time I've manoeuvred out of my car tent it's heated up enough to find the gears with some effort. I've reached out to California push/pull to have cables that are several inches longer than the ones I'm using, to be able to route them much further from the exhaust. The shift and select cables are sitting with the shift on top, and select between it and the y pipe heat shield, pretty tight against it, so it makes sense that the select is having problems and not the shift. Otherwise the engine bay heat is very normal, I had people at autocross comment that it was much cooler than expected, opening the trunk after a run. The turbo being directly beneath the decklid vent definitely helps there, the heat rises up and straight out, asking with the airflow when moving.
I have been working on the ve table, getting things leaned out significantly, and normal driving more efficient, that's going pretty well. I also did more looking into the spark tables and compared what I had (fairly close to an older table from PMBrunelle), and the original 2.8 table as shown in the book "High Performance Fieros", and the stock table has spark advance much much higher than I was running. I don't know what PMBrunelle has settled on at the moment, but for the last few days I've been running the stock table in the vacuum section, and I haven't noticed any pinging/noises/whatever. I haven't necessarily noticed a power improvement, because when I'm heavily scrutinizing all the sounds and whatnot coming from an engine, I don't notice power differences, I will likely switch the tune back and forth a few times to compare when I'm not specifically scrutinizing everything else. I'm also experimenting a little bit to try and get back the burble my stock engine and my dad's Fiero had, I haven't finished that, but that's why I have some very retarded parts at the bottom.
This is my current spark table, based as close as possible to the Fiero original, erring on the side of less though for in between values where the tables didn't line up.
The book values for the stock table:
I've done a few 0-60s, and they are now a consistent 5.5-5.7 seconds, now they are not GPS/app based, instead coming directly from the datalog, as real time from 0 to 60 (0-96.5km/h), so no arguing it's validity this time haha! Speed is not calculated by pulses per mile because that changes with the tire, instead it's calculated directly by advertised tire outer diameter (from manufacturer), and the number of teeth on the speed sensor (29). This has been verified with phone GPS across several speeds as being accurate within 1km/h, and the speed signal to the dash is just a 4000 ppm output from the ECM, and the dash is also surprisingly accurate (I didn't have to fiddle with the ppm settings to get it accurate). If I recall the app 0-60 number when PMBrunelle took me for a drive in the White Bug, it was also about 5.5 seconds, but he was going really easy on the 4 speed, that will likely be improved with the 5 speed.
I've been using 10w40 oil so far, but the selection is horrible, basically all there is in my area is Castrol conventional, and I am wanting to go to synthetic or semi synthetic, and there don't seem to be any options for that unless I want really pricey racing stuff that's like $75 for a jug. This is a roller camshaft, so zinc and whatnot don't matter as much as a stock 2.8. there's 15w40 diesel oil available for about $50 a jug, and 10w30 Mobil 1 synthetic on sale for $36. How strict are the oil requirements?
My rod bearings measured at 0.001", spec is 0.0007-0024", so I'm within the lowest fifth of the spec, mains are 0.0015-0020", spec 0.0008-0025", do I need 10w40 or heavier, or is a better quality synthetic 10w30 going to be as good or better than the cheap conventional 10w40?
[This message has been edited by 1985 Fiero GT (edited 08-17-2025).]
Originally posted by 1985 Fiero GT: My select cable is freezing up when the engine is cold, it is the one nearest the exhaust, so I believe that it has somewhat melted, when hot, it is still sticky but not frozen. So far that has not impacted driveability to much, I park it in the gear I'll next need, by the time I've manoeuvred out of my car tent it's heated up enough to find the gears with some effort. I've reached out to California push/pull to have cables that are several inches longer than the ones I'm using, to be able to route them much further from the exhaust. The shift and select cables are sitting with the shift on top, and select between it and the y pipe heat shield, pretty tight against it, so it makes sense that the select is having problems and not the shift.
You might try dripping some motor oil into the select cable. On my Muncie, the Rodney Dickman cable became sticky with engine heat. Oil was a pretty long-term fix, only needing to be re-applied after maybe two years.
quote
Originally posted by 1985 Fiero GT: I also did more looking into the spark tables and compared what I had (fairly close to an older table from PMBrunelle), and the original 2.8 table as shown in the book "High Performance Fieros", and the stock table has spark advance much much higher than I was running. I don't know what PMBrunelle has settled on at the moment, but for the last few days I've been running the stock table in the vacuum section, and I haven't noticed any pinging/noises/whatever.
The less dense the air/fuel mixture, the slower the flame propagates through the combustion chamber, so the more spark advance is needed to maximize work on the piston. The stock timing table reflects this tendency.
This is what I was running last with the Muncie (such as during the ride I gave you):
Below 55 kPa in the lower RPM ranges, I'm having the timing advance become more retarded rather than more advanced. I was having bucking/oscillation problems at low throttle, and shaping the timing table like this (retard in the problem area, with gentle transitions to the rest of the table) mostly fixed those problems. This behaviour was sometimes implemented on older cars with the vacuum advance canister being connected to a ported vacuum source, rather than to manifold vacuum, sometimes to reduce NOx emissions at low throttle.
If you don't have driveability problems, then there's no reason for you to shape your timing table like this.
With my Getrag F23, I expect to cruise on the highway at lower RPMs, perhaps around 2500 RPM, so I adjusted the spark timing table to have more advance in that area than before:
This will need to be tested when I get my car running again.
How does the car drive if you keep the MAP between 17.5 kPa and 25 kPa? Does the timing jump around too much?
quote
Originally posted by 1985 Fiero GT: I've been using 10w40 oil so far, but the selection is horrible, basically all there is in my area is Castrol conventional, and I am wanting to go to synthetic or semi synthetic, and there don't seem to be any options for that unless I want really pricey racing stuff that's like $75 for a jug. This is a roller camshaft, so zinc and whatnot don't matter as much as a stock 2.8. there's 15w40 diesel oil available for about $50 a jug, and 10w30 Mobil 1 synthetic on sale for $36. How strict are the oil requirements?
My rod bearings measured at 0.001", spec is 0.0007-0024", so I'm within the lowest fifth of the spec, mains are 0.0015-0020", spec 0.0008-0025", do I need 10w40 or heavier, or is a better quality synthetic 10w30 going to be as good or better than the cheap conventional 10w40?
Thicker oil is basically insurance against failure at the expense of higher drag (and hence reduced power / fuel economy).
You don't have extreme pressure in your engine, but you do have a turbo, so to prevent oil coking in the turbo, synthetic would be a good idea.
If you can only have the synthetic oil in 30-weight, I would prefer to stick with the 40-weight conventional. I would prefer to protect the engine more at the expense of risking oil coking in the turbo, which is more easily/cheaply replaced.
You might try dripping some motor oil into the select cable. On my Muncie, the Rodney Dickman cable became sticky with engine heat. Oil was a pretty long-term fix, only needing to be re-applied after maybe two years.
I will try that, I've now driven about 350 kms like this, it heats up and unsticks quickly, but when fully cold is immovable, I'll try oiling it.
quote
Originally posted by pmbrunelle: Below 55 kPa in the lower RPM ranges, I'm having the timing advance become more retarded rather than more advanced. I was having bucking/oscillation problems at low throttle, and shaping the timing table like this (retard in the problem area, with gentle transitions to the rest of the table) mostly fixed those problems. This behaviour was sometimes implemented on older cars with the vacuum advance canister being connected to a ported vacuum source, rather than to manifold vacuum, sometimes to reduce NOx emissions at low throttle.
If you don't have driveability problems, then there's no reason for you to shape your timing table like this.
With my Getrag F23, I expect to cruise on the highway at lower RPMs, perhaps around 2500 RPM, so I adjusted the spark timing table to have more advance in that area than before:
Ok, makes sense. For your tires (255/40R17?), should theoretically be ~2350 rpm@100 or ~2575@110km/h
quote
Originally posted by pmbrunelle:How does the car drive if you keep the MAP between 17.5 kPa and 25 kPa? Does the timing jump around too much?
That is almost impossible to do, it idles at 28-30kPa or so, and 0% throttle engine braking is 15-20kpa, I've only seen 10kPa in the datalogs a couple of times, at the initial release of the throttle after an acceleration, before the idle valve starts to reopen. When driving, the only time I see the timing starting to retard is when I am fully or almost fully engine braking, but certainly not at any point where I am cruising/maintaining speed.
quote
Originally posted by pmbrunelle:Thicker oil is basically insurance against failure at the expense of higher drag (and hence reduced power / fuel economy).
You don't have extreme pressure in your engine, but you do have a turbo, so to prevent oil coking in the turbo, synthetic would be a good idea.
If you can only have the synthetic oil in 30-weight, I would prefer to stick with the 40-weight conventional. I would prefer to protect the engine more at the expense of risking oil coking in the turbo, which is more easily/cheaply replaced.
And does synthetic not have better load capacity etc. than conventional? That doesn't have enough of an impact to let a grade thinner synthetic perform as well as a grade thicker conventional? I guess I'll have to keep an eye out for synthetic or semi synthetic 10w40.
Originally posted by 1985 Fiero GT: And does synthetic not have better load capacity etc. than conventional? That doesn't have enough of an impact to let a grade thinner synthetic perform as well as a grade thicker conventional? I guess I'll have to keep an eye out for synthetic or semi synthetic 10w40.
The viscosity of the oil (together with the rotation of the crankshaft) keeps the shaft centered within the bearing. The amount of load the oil can take without squeezing out and having metal-to-metal contact depends on the viscosity.
Besides the resistance to breakdown, I do not know enough about the difference between conventional and synthetic to comment intelligently.
The viscosity of the oil (together with the rotation of the crankshaft) keeps the shaft centered within the bearing. The amount of load the oil can take without squeezing out and having metal-to-metal contact depends on the viscosity.
Besides the resistance to breakdown, I do not know enough about the difference between conventional and synthetic to comment intelligently.
We have to take into account how those viscosities behave when heat is applied to the oil via work of the engine. A 10w-30 at 200F is not 10W-30, it's way thinner than that. That means if the oil's temp keeps increasing due to the work load demand of the engine (a turbo puts lots of heat on the oil) what you end up is an oil with the viscosity of water, in other words no protection. Even if you have the perfect bearing clearances for that thin oil, that thin film has no shear strength. That's why if you decide to use a turbo and autocross and do track weekends or whatever, the best insurance like you mentioned Patrick is to go for the thicker option. 10W-40 is the minimum I use in my engines. For dyno tuning and track I use Valvoline 20W-50 VR1 full synthetic, Scheaffer racing oil10W-40 and 20W-50.
Now, the main advantage of full synthetic oil is besides being way more slippery than conventional is the way it deals with the heat. Compared to conventional oil, synthetics have a much higher viscosity index. Viscosity index refers to how the oil changes viscosity with heat. The higher the index the slower and gradual the change in viscosity as the oil heats up thus maintaining its shear strength film longer. This index gets reduced as the oil goes through heat/cold cycles and contamination from combustion residual in the crankcase. That's why if you are going to go to do some track days or autocross and you have 2 months with that oil, protect your investment and get a new oil change before beating on your engine. Another important aspect of conventional or synthetic is the additive package they use. There are conventional oils out there that outperforms all the "Full Synthetic" Castrol and Mobil 1 that you can buy in convenience stores.
The viscosity of the oil (together with the rotation of the crankshaft) keeps the shaft centered within the bearing. The amount of load the oil can take without squeezing out and having metal-to-metal contact depends on the viscosity.
Besides the resistance to breakdown, I do not know enough about the difference between conventional and synthetic to comment intelligently.
quote
Originally posted by La fiera:
We have to take into account how those viscosities behave when heat is applied to the oil via work of the engine. A 10w-30 at 200F is not 10W-30, it's way thinner than that. That means if the oil's temp keeps increasing due to the work load demand of the engine (a turbo puts lots of heat on the oil) what you end up is an oil with the viscosity of water, in other words no protection. Even if you have the perfect bearing clearances for that thin oil, that thin film has no shear strength. That's why if you decide to use a turbo and autocross and do track weekends or whatever, the best insurance like you mentioned Patrick is to go for the thicker option. 10W-40 is the minimum I use in my engines. For dyno tuning and track I use Valvoline 20W-50 VR1 full synthetic, Scheaffer racing oil10W-40 and 20W-50.
Now, the main advantage of full synthetic oil is besides being way more slippery than conventional is the way it deals with the heat. Compared to conventional oil, synthetics have a much higher viscosity index. Viscosity index refers to how the oil changes viscosity with heat. The higher the index the slower and gradual the change in viscosity as the oil heats up thus maintaining its shear strength film longer. This index gets reduced as the oil goes through heat/cold cycles and contamination from combustion residual in the crankcase. That's why if you are going to go to do some track days or autocross and you have 2 months with that oil, protect your investment and get a new oil change before beating on your engine. Another important aspect of conventional or synthetic is the additive package they use. There are conventional oils out there that outperforms all the "Full Synthetic" Castrol and Mobil 1 that you can buy in convenience stores.
Interesting, I will have to try to figure out more research on this, because if 10w30 synthetic has a better shear strength at temperature than 10w40 non synthetic, then I might as well get that. I will also look more for synthetic or semi synthetic 10w40 around here.
