I have around 100 miles on my motor , waiting for the cam to wear in before I swap rockers. I am still deciding on which ratio to get because I have ported lower , middle , and a dual throttle body upper intake. Along with some other minor things but that's pretty much the biggest improvement for hp potential so far. I still have the stock heads, which I should have maybe did some work on but I kept things simple and it was part of an already assembled long block. I wont bother with head or cam work unless I eventually put in a 3.4
From what I have already when I do decide to do my rocker swap should I go with the 1.6 vs the 1.7 , I cant remember the source but there was dyno results from 1.6 and 1.7 rockers on a stock fiero and the 1.6 gained more in the bottom end , leading to more average hp. Even though the 1.7 got a few more peak hp. This leads me to want to go with the 1.6 due to the less cam pressure BUT... what HP difference do you think there will be at peak on my particular motor? So I can decide if it might be worth it to go with the 1.7's
Also from what I have read its a direct swap , have also read some people talk about already pretty close to max valve lift and the rockers will cause a problem without the springs. So could anybody give me more info and point me into the right direction?
I'm guessing you're talking about a 2.8 V6? If that's the case, then there are no commercially available 1.7:1 rocker arms that will fit it. At least, there are none that I know of. But 1.6:1 rocker arms are readily available. So the situation basically takes care of itself.
The stock valve springs should work with the 1.6:1 rockers (assuming a stock camshaft). But the Comp Cams #980 springs would be better. They're stronger, and can handle more valve lift. That said, keep in mind that a stock camshaft with 1.6:1 rockers is going to be roughly equivalent to a mild performance camshaft with stock rockers. If you plan to do some more in-depth performance mods in the future, then you may want to hold off and get a better camshaft instead.
Also, keep in mind the stock 2.8 V6 heads don't flow very well. No matter what you do with the rest of the engine, the heads are going to hold it back. You may want to look around for someone who can do a good port job on them.
There was a link to the Chevrolet Power Catalog in a post somewhere on PFF. Maybe somebody could post the link. But when you port the heads, use 8mm stem intake valves so you can thin the intake fin a tad. DO NOT LET ANYBODY REMOVE THE FIN. It splits the air around the valve stem and will dramatically decrease air flow. On my first Fiero (86 SE), I had the heads ported and polished. They removed the fin and the car was noticeably slower than my 86 1/2 GT "fastback" (a heavier car). Both automatics. GT was completely stock. The SE had aftermarket free flow cat and matched exhaust port to header. I could tell the before and after when I got the car back.
It's a myth that iron heads don't flow. Without even using 8mm valve stems, they've flowed 182 cfm which translates to close to a 300hp potential using standard accepted formulas for hp per cfm per port...
Even if your heads were ported to flow that much, the limit is still defined by your cam. If your cam is only doing .440" lift, what's the point of looking at the .600" lift flow rate? That's why I say the heads don't matter because the actual running net lift is crippling most engines.
With flat top pistons, iron heads are limited to .510" of lift. With the thicker 3400 gasket (.080" vs. 3.4's .040") you can go higher but lose about .15 compression ratio. Obviously, you'll need springs to support that...
As for the valves, there are 2.8 valves from the 87-89 AL head 2.8 that use 8mm valve stems. There is also a 1.76" intake valve that may be used as well but I ran out of time to look into it. That would require machining the bowls. The 1.76" valve would also increase compression a bit just like going from the 1.6/1.3 to 1.72/1.42 made the 2.8 go from 8.5->8.9 compression, but less so since it's only the intake valve going from 1.72" to 1.76". The thicker gasket would offset that. These are the little tricks that the AL heads come with as "stock" that make them flow better, not some magical port casting design like many are lead to believe.
[This message has been edited by lou_dias (edited 06-03-2014).]
It's a myth that iron heads don't flow. Without even using 8mm valve stems, they've flowed 182 cfm which translates to close to a 300hp potential using standard accepted formulas for hp per cfm per port...
These are the little tricks that the AL heads come with as "stock" that make them flow better, not some magical port casting design like many are lead to believe.
Little tricks... ok. Let's look at some documented examples of iron head work...
La Fiera removed the vane and you can see the poor results at low lift, due to the loss of velocity, and how it recovers at the high end... but such a sound... (BHP also did his heads with the CNC so it is an excellent example of the intake vane's effect compared to their other heads...)
Now, let's take the BHP heads from above, which show the best, and admittedly damn fine, improvements and compare them to stock Gen III 3400, 3500 and WOT-TECH's ported 3500 aluminum heads.
Unfortunately, when compared to even stock 3400 heads, they only manage to exceed flow is at .200 lift at the intake port. The design of the iron heads will not allow them to flow as much as the Gen III aluminum heads... the geometry simply isn't there.
[This message has been edited by carbon (edited 06-04-2014).]
I have around 100 miles on my motor , waiting for the cam to wear in before I swap rockers. I am still deciding on which ratio to get because I have ported lower , middle , and a dual throttle body upper intake. Along with some other minor things but that's pretty much the biggest improvement for hp potential so far.
Did you just compare La Fiera's 2.8 to a 3500? Awesome.
Did I post his flow numbers? Yup. Did I compare his heads to the 3500? No, I compared BHP heads with the vanes to the 3400/3500 heads.
3.4L and 2.8L iron heads are identical. If you are going to say that mythical iron heads flow just as well as aluminum heads, and the 3500 heads can be put on a 3.4L, then yes, I am going to post the numbers. Especially since the OP mentioned swapping to a 3.4L as a future plan.
Every time this conversation comes up, you state that iron heads can flow just as well as aluminum heads, and then, when some one refutes you, you guffaw at a real comparison. Your assertion that ported iron heads can flow just as well as stock 3400 heads is false. BHP's heads are awesome examples of an iron head porting job, picking up lots of flow almost everywhere, but they still fall short of stock 1996-2005 3400 flow numbers.
Please continue to tell us how the numbers don't matter and regale us with more anecdotal stories about messed up dyno pulls and tuning problems.
[This message has been edited by carbon (edited 06-03-2014).]
Did I post his flow numbers? Yup. Did I compare his heads to the 3500? No, I compared BHP heads with the vanes to the 3400/3500 heads.
3.4L and 2.8L iron heads are identical. If you are going to say that mythical iron heads flow just as well as aluminum heads, and the 3500 heads can be put on a 3.4L, then yes, I am going to post the numbers. Especially since the OP mentioned swapping to a 3.4L as a future plan.
The thing about La Fiera is he loves what he built and didn't make excuses. It is what it is, and his intake work was awesome.
Yes, but he did remove the vane. And doing the math, using 1.76" valves and 8mm valvestems opens up 5.5% more area on an iron head. Regardless, you put 28" 182 CFM, 6 cyclinders and 207 cid into any horsepower calculator and you'll come out with more horsepower than most anyone is making because almost no one is running .600" of lift. That is why I will always say the heads are not the restriction and that's what you can't grasp.
Yes, but he did remove the vane. And doing the math, using 1.76" valves and 8mm valvestems opens up 5.5% more area on an iron head. Regardless, you put 28" 182 CFM, 6 cyclinders and 207 cid into any horsepower calculator and you'll come out with more horsepower than most anyone is making because almost no one is running .600" of lift. That is why I will always say the heads are not the restriction and that's what you can't grasp.
You obviously only read what you want to read... I only listed La Fiera's heads to demonstrate the importance of the vane, as was mentioned in a previous post. The comparison to the aluminum heads was not made with his numbers.
Show me where I referenced .600"? Show me where the MAX EFFORT iron heads be the stock 3400 heads anywhere but .200"?
At .300" 133.8 * 1.055 = 141.2 for the iron head vs. the stock 152.0 of the 3400 head and its only short by 5CFM at .400". Tell me again how 5.5%, while a good gain, changes the picture. This is still all comparing heavily modified to stock. That is what you can't grasp, I guess.
[This message has been edited by carbon (edited 06-03-2014).]
I do not plan on doing a cam in the 2.8 , but in the future I might put in a 3.4. Which is why for ease of swap and cost rockers are the way for me to go, because I am not tearing into this motor or doing head work, its already together and runs.
I'll leave cam+rocker+head work combo for the future 3.4 , sounds like in this 2.8 I will be going with the 1.6's and maybe might go with the stronger springs as well.
I didn't know there weren't 1.7's available to put into the fiero, being that there was a write up on a popular car website that did a dyno comparison... Too bad I cant remember which one to source it. But even so the 1.7's that have found that could possibly be retrofitted cost 3-5x + more than the 1.6's I have sourced so I guess 1.6 it is.
I like the intake, however few things I would change to it.... and for people who are still interested in TLG products that are still available. The shaved thermostat that loses the throttle body coolant lines , If you do so , you lose your bracket for your map sensor... Right now its just hanging from the vacuum hose and electrical plug around a bracket. So be prepared to already have a way figured out to mount it. I threw away my old coolant lines so I don't know if I could take the bracket off the lines and mount it to the dog bone bracket or not. But that would be nice...
The brake booster vacuum line runs in a hard to install position under the main section of the upper intake between the runners , I don't like it but thats how it has to be until I maybe change some things up and lengthen the hose and use some way to mount it out of the way. I don't like it touching the intake , there are not enough vacuum ports on the intake so a Y piece is sent to connect the vacuum booster hose and the fuel pressure regulator onto one nipple on the intake .... The size of the vacuum booster hose does not fit perfectly onto the end so I built it up with layers of electrical tape and used a clamp. Also due to the length and position you have to run the vacuum hose for the booster It makes the fuel pressure regulator hose have a S bend not really kinked but I don't believe it to be optimal
If you put the intake on an 88 , you have to file out some of the decklid ribbing towards the firewall to be able to close it... The intake pipes have to be angled a particular way to fit under the decklid maybe I can fiddle with them some more later on but the oxygen sensor wire has to be zip tied to other wires to hold it out of the way from the exhaust.
The throttle body toward the trunk interferes with access to the distributor , which means its alot easier to take off the throttle body to get access to change the plug wires , change the position , and depending on which teeth you are into the drive gear of the distributor the throttle plate piece where the spring is for the return can interfere with full WOT unless you position everything just right regarding boot angle and distributor angle. Removing the throttle body is pretty easy to remove however but annoying
The extension plugs for the TPS has to go over and around other wires and hoses to avoid contact with the exhaust
But overall the intake is pretty good unsure of any gains as of yet , haven't drove a stocker.... just wish there was more improvement phases before production , mainly things that are not cleaned up looking and although work just makes things look like a mess, thrown together, and may eventually cause future problems..... Which I am going to be taking time to try to correct.
I am going to heat coat the trunk and depending on the durability etc inside and outside trunk area with bed liner and or lizard skin insulation and sound deading or other cost effective identical products. Port the crossover pipe since its already got a hairline crack , go with 1.6 rockers and do a better job insulating the exhaust because the intake , intake tubes and valve covers get too hot to touch. I might gut the cat but if I do it will be after every other performance thing is done unless I have an issue with it.
[This message has been edited by Winfield1990 (edited 06-04-2014).]
Sorry Blacktree... misinformation is the best information I guess. I'll never point it out again.
My comment was mainly pointed at Lou. It seems like every thread where anything about cylinder heads is mentioned, he runs off at the mouth. It's getting really annoying.
Edit to add: yeah, I want to see pics of the intake too.
[This message has been edited by Blacktree (edited 06-04-2014).]
My comment was mainly pointed at Lou. It seems like every thread where anything about cylinder heads is mentioned, he runs off at the mouth. It's getting really annoying.
Edit to add: yeah, I want to see pics of the intake too.
The subject had to do with lift and valves on iron heads and I talked about how to improve flow in iron heads. There was no need to post aluminum head flow numbers when those aren't the heads being discussed. Oh yea, I totally ran off at the mouth... I only mentioned aluminum heads with regarss to a same-feature upgrade that can be done to iron heads. Why is it that every time someone mentions iron heads, someone has to come in and say aluminum heads are so much better? Who's really doing the trolling here?
[This message has been edited by lou_dias (edited 06-04-2014).]
Also more info if anybody wants to know what all vacuums I have hooked , 2 nipples onto the bottom of the firewall throttle body which are EVAP + another hose cant remember what for at the moment , on the intake tube that runs between the intake main sections , there are 3 more nipples , pcv , map , and then the last nipple vacuum boost + fuel regulator. I ordered my intake without EGR , its removed and disabled in the prom.
[This message has been edited by Winfield1990 (edited 06-04-2014).]
Nice that you have one of those... not a whole lot of them made it into the wild. Yours is only the third one I've seen. Thanks for the pics and the rundown on the install. Almost nothing is as straight forward as it looks.
quote
I threw away my old coolant lines so I don't know if I could take the bracket off the lines and mount it to the dog bone bracket or not. But that would be nice...
If you still have the throttle body coolant lines you can cut the bracket off with a dremel tool and bolt it back on to the stock intake, of course that doesn't work with the dual TB intake, but that is what I did when I removed my lines. I don't have the TLG housing, I just looped the lines with a small hose.
I only mentioned aluminum heads with regarss to a same-feature upgrade that can be done to iron heads. Why is it that every time someone mentions iron heads, someone has to come in and say aluminum heads are so much better? Who's really doing the trolling here?
We all read this forum, I tend to key on threads based on 60* engines because I am a fan, I'm not into V8s or 3800s. It has nothing to do with trolling. You have a ton of knowledge about iron heads and what it takes to get the most out of them, and I have no problem with anyone using them. I did nothing but compliment BHP's port work, as it is excellent work based on stock flow numbers.
If all you had ever said was you could get iron heads close to the same flow characteristics as the stock 3400 heads, I would have nothing to say. But to state, as fact, that the Gen III aluminum head design being superior is a myth people have been lead to believe... you are just asking people to refute you. I only posted the ported 3500 numbers to show what the same amount of work gets you when you start with a mythical head.
(BHP also did his heads with the CNC so it is an excellent example of the intake vane's effect compared to their other heads...)
Got pics?
I don't have the TLG housing, I just looped the lines with a small hose.
