Turbo 3400, F23 build, 1985 GT (Page 23/26) 1985 Fiero GT JUL 14, 09:52 PM quote Originally posted by fieroguru: 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? fieroguru JUL 14, 10:00 PM quote 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. 1985 Fiero GT JUL 14, 10:06 PM quote Originally posted by fieroguru: 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. fieroguru JUL 14, 10:12 PM 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. 1985 Fiero GT JUL 14, 10:31 PM quote Originally posted by fieroguru: 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. 1985 Fiero GT JUL 14, 11:39 PM 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? pmbrunelle JUL 15, 06:23 PM quote 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. 1985 Fiero GT JUL 15, 06:33 PM quote Originally posted by pmbrunelle: 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. 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 will be sure to keep an eye on that. 1985 Fiero GT JUL 15, 11:09 PM 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. 1985 Fiero GT JUL 22, 12:36 AM quote Originally posted by 1985 Fiero GT: 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. Cyl 1: 110 psi Cyl 2: 125-130 psi Cyl 3: 150 psi Cyl 4: 135 psi Cyl 5: 130 psi Cyl 6: 135 psi 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!