3.1 gen II pistons in gen 3 motor? does it work?

[farmerz24]

hi all,

i cant remember if the gen2 pistons will work in the gen 3. of course compression ratio is reduced correct? will it give me 8.9:1 or a similar compression ratio to the 3.1?

i am looking for a cheap alternative to handling 8-10 psi of boost and was going to go with hyperutectic 3.1 gen 2 pistons if they reduce the compression ratio, but am unsure as to if they will work.

is the pin hieght the same and will they come out of the block the same amount? someone please let me know.

im also running milzy's stage 1 cam, 520 lift, is this going to interfere with the piston?

Thanks all.

[RacerX11]

Gen2 pistons will put the compression right about what a gen2 3.1 had. I would not do this, as you are dropping about a half point of compression, but losing the quench design of the gen3 pistons. For a boosted engine, the quench would be more important than a half point drop in comrpession.

Marty

[farmerz24]

ah, well then in that case can i get hyperutectic's with a lower compression ratio and still keep the quench design? or am i limited to stock comp. hyper pistons?

i dont suppose thicker head gaskets are made for this (that arent copper), not looking to o-ring the block on this motor.

thanks

[FallenZ24]

Yes they fit. It'll lower the c/r to 8.9:1

Personally I wouldnt do it. You would be slower than a stock 3400 when not in boost. You can run 8-10 psi reliably on a 3400. You just need the fuel upgrades and tuning to do it.

[farmerz24]

do you think the same holds true for the 3100? (8-10 psi) im currently running around 7 right now maxing out my 30lb ford injectors, going to put in gtp 36 hi imp ones hopefully this will work well.

above 6g it backfires/cuts out becuase it is so lean

[Syn]

fallenz24 is right, i'd go that way as well. a few guys on v6z24.com are doing it.

my 3.1 pistons are stock and i even plan on 8-10psi but with a good tune


farmer whats ur setup look like?

[IsaacHayes]

A 3100 is the same as a 3400 except for less displacement. That is unless you are talking about a 94-99 3100. In that case it has smaller intake valves, and smaller intake manifolds (but still the same design). It won't flow as well but still waaaay better than a stock gen2 3.1mpfi.

Keep in mind too that if your sprigns are stock, you'll get valve float when you approach 10psi or so.

[farmerz24]

im runnning a 98 3100, but with all large port heads, intakes, 3500 intake and 70mm tb, 1 5/8 custom headers into 2.5 collectors y'd to the turbo and 3 inch exhaust.. this is on a third gen 2000 cavalier 5 spd.

the heads have been ported by v6 ho, im running milzy's stage 1 turbo cam with ls6 springs. 36lb gtp injectors managed by a holley commmander 950.

turbo is a t3 stage 3 .82 ar exhaust, 60-1 compressor.

i would like to lower my c/r a little say 9.0 or even 8.9-1. i can stand to loose a little off boost response. especially since i may add a m90 to this mix as well.

but, do they only make the stock compression piston in a hyperutectic or can i get custom deeper dish for slightly lower compression?

anyone?

[IsaacHayes]

NICE setup on the motor. That's like a 2000+ 3100 then, with lots of goodies.
Did you see the custom piston group buy on v6z24.com? Custom pistons you can get with reduced compression, or higher compression. Not sure if they are shaped like the gen3 ones or not, maybe the style is an option?

You might go with an eaton and turbo?!?!? That's crazy, not crazy as in for doing it, but pick one or the other man. You'll make plenty-o-power with just the turbo, or just a supercharger. Now if you had a RWD car with a super beefy trans/etc and the room, then I'd say go for it... But yeeesh! If you are going to go super complex with both, I'd go for a smaller supercharger with an electric clutch. Put a window switch on it so it engages at idle up to where your turbo spools, then switches off. Some mercedes had small eatons with clutches on them. That way you'd have instant boost from idle then when the small s/c starts to drop off, it's turned off freeing up horsepower by not turning anymore and the spooled up turbo picks up the duty. Maybe even put a pressure switch that once it sees boost it will keep the eaton off too so when you shift the eaton doesn't come back on since the turbo will still be spooled. Like I said this is pretty overkill for a fwd setup. Something I'd do on a rwd or mid engine rwd car with a bullet proof trans. driving that thing without it lighting up the tires with that setup would be really hard!!!

And I can't believe you stuffed that motor into the gen3 j-body!! I've seen it done before, but man the stock 4cyl is a tight fit!! Let alone with a turbo in there!!! Mad props, but I wouldn't want to work on that motor in there!! The 3rd gen J body is pretty light weight like the old ones right?

[farmerz24]

the 3100 is actually a good fit, more room in the back than the 4 due to the short compact design.

oh yes, i also have poly 1 inch risers on the intake manifold to make the 3500 runners 1 inch longer and isolate from heat.

with the group buy, thoes are for forged pistons which means my motor must be re-bored. i just want something i can drop in (for now). ill get some pics up of the finished setup (waiting for my water injection). eventually i will be building a 3400 and thats where the forged pistons will go.

with the twincharged setup you run the turbo into the sc both are always engaged, the sc never becomes a restriction. it also helps to spool the turbo quite fast.

but ya, so i guess im limited to stock compression hypers then eh? where can i get these? who sells them? preferabbly in canada.

[Syn]

it looks like you got a good amount of work into your setup why not stay with stock cr? my other car i ran 10psi on 9.5:1 no prob

also twincharged cars are pretty cool i've seen a ion like that