Project 91 "SS" 3400/5spd

[woody90gtz]

Stock pistons are dished... that sucks. I assumed they were flat tops (given all their inherent advantages). 10.75 dynamic and 91 octane with dished pistons seems impossible to me... but I can be sure because I havent done the research, and you seem to know what you're talking about.

Extra power seems worthless to me right now anyway. I decided to go out and have some fun with the "SS" before I put it up for winter and wow... I can't get the tires to hook for crap. The limited slip pulls too hard to do a burnout, but dumping the clutch at any rpm is impossible to do cleanly. Even a rolling 1st gear WOT blast gives me wheel spin. It did only wheel hop once, but that was with the ebrake on. Here's a vid of a clutch dump at about 2500. I'm thinking (hoping) that maybe the tires are just too damn old to bite. New ones are coming in the spring anyway.

"Tractional difficulties"
http://vids.myspace.com/index.cfm?fusea ... =100162619

[99GaGT3X00]

You can go with MLS headgaskets at .030 and 3.4 gen1 iron head pistons for .040 quench (stock gasket is .040 and .050 quench on iron head) but then you end up with 12.73:1 static compression with 3500 heads. If you run .060 3500 head gaskets you end up with 11.5:1 and .070 quench. The 3.4 DOHC had .070 quench stock believe it or not at 8.81:1 static compression. If you use the pistons from that you'll have even higher compression.
.

ok so lets say i go with the 3.4 ironhead piston and a 3500 MLS head-gasket with a thickness of .035 and get a CR of 12.52.1 with an ideal quench of 0.045 ill be good right. i already picked up the piston way back when i first swapped the newer 3400 in.

so trying the 3400 head-gasket bore of 3.75 vs the 3.80 of the 3500 it brings a 12.56.1 CR not much of a difference there and it doesnt affect the quench. ok so the MLS gaskets are actually a 3.72 bore for the 3500 but still that only brings it up to 12.58.1. ive been playing around with this for awhile and never got a positive answer from anyone on waht would work without problems.

ok if this will work without giving me problems and by problems i mean valve to piston contact and other ill effects. this setup would give my cam the high compression it wants and would make it perform nicely and keep me from buying a fatter cam.

sorry woody for the further thread derailment just picking you guy's brains.

[Cliff8928]

Extra power seems worthless to me right now anyway. I decided to go out and have some fun with the "SS" before I put it up for winter and wow... I can't get the tires to hook for crap. The limited slip pulls too hard to do a burnout, but dumping the clutch at any rpm is impossible to do cleanly. Even a rolling 1st gear WOT blast gives me wheel spin. It did only wheel hop once, but that was with the ebrake on. Here's a vid of a clutch dump at about 2500. I'm thinking (hoping) that maybe the tires are just too damn old to bite. New ones are coming in the spring anyway.

Yeah, that's about how mine is in the cooler weather, and that's with 245s.

[Asylum]

See what an LSD does.

It can actually make wheel spin worse with a little power and the inability to hook it up.

That is one of the reasons I seldom drive my 3500. It just spins the tires everytime you get a little heavy on the gas. Although Goodyear Eagle F-1's SUCK at straight line anything! But at least it goes straight.

Drag radials or slicks if you ever expect decent times from that thing Woody.

[woody90gtz]

The wheel spin isnt any worse than it was with the Z26... that thing was ridiculous with the cut out closed.

When I drove Geoffs it hooked pretty well with the same size tire & LSD, but maybe part of that is due to his heavy-ass brakes.

Maybe I'll have to beg, borrow or steal a pair of DRs at the strip some time to see if I can run any numbers. I'll also have to adjust my ebrake a little tighter I think. The video of my burnout attempt has the back wheels turning, not dragging.

[Barry]

Run it at the track on streets it should hook. Mine usually won't spin first with a very very light launch.

[Asylum]

Barry is right. The track is a whole different world than a sidestreet.

Especially a well prepped track. I actually was able to run high-14's on an old set of Dean Stingers up to last year.

DR's FTMFW!!

[IsaacHayes]

Also, I wonder if you guys have trouble due to running 17's... Even less side wall means less flex... Sure handling feels nice and crisp but no give means no give...

I wonder how your car would do with some wide street tires on 15's....

Here is what the pistons look like:
Oh, and 10.75 dynamic works on 93 octane. That's what Johnnymossville's motor ran on.

[woody90gtz]

My 17s worked good enough for 14s with the same tires, but that was also 3 years ago when they werent so damn old.

So the stock pistons suck for quench. Definitely makes up my mind against 3500 heads.

[3X00-Modified]

I'm confused on why you think the dish itself is a cause to think the quench ability sucks... Look at the cylinder head... how much flat surface is there exposed to the top of the piston?



The area of the head that would even come into play with quench isn't all that large to begin with, so I really doubt that the dish on the piston makes them alone suck for quench.

Your best combo would be to get a set of forged 10.5:1 3400 pistons and combine that with 3500 heads, IIRC that comes out damn near close to 9.8:1 on a 3400/3500 setup, but as you noted you don't feel that power is necessary. Remember it might have to do with your 12.635 gear ratio now, vs your old 8.55 ratio on why you only spin tire.

[Barry]

I put crappy 195's on 14 inch steelies on my z26 to see how they hooked up. It makes me feel like a beast spinning all of first, second, some of third, and chirp 4th at like 90mph. Its nuts.

[IsaacHayes]

Jon has a good point. There is not a whole lot of flat space on the head, but if you wanted to go all out on the best possible setup you could have, you would go for flat tops to get the extra bit that is not covered by the outer edges of the stock pistons. There isn't a TON there, but it is a fair amount if you consider how little you get anyway.

Barry, I find it harder to spin all season 185's believe it or not than my 225's.... Figure that one out...... And if I'm at 30psi on my 225's, they spin easier than when at 35psi......

[Barry]

Well theres a point where if you go too wide you will loose traction, but I dont think 225's are near that point.


Im all about the 1 wheeler pealers!

[woody90gtz]

Jon, are those tan areas completely flat? It's hard to tell in the pic but it doesnt look like it, and I would think they should be for good quench. In this pic you see the flat area of my Vortecs where the .040 quench with flat tops comes in to play.


I guess I just do not know much about the 60*v6. I should join that board.

A wheel spin problem sure is a fun one to have though. haha

[3X00-Modified]

This a better image to see it?



More just the yellow areas of the head in the last post.

So it's only really the ring area of the dished piston that even has a flat surface above it, the rest of the head is the heart shaped chamber.