Batass

Im planning on building a supercharged vortec engine. What dish pistons should I use to maintain no higher than a 9:1 cr with a 383? Is there a certain kind better than another such as D-shaped? I know its going to be a big dish with 64cc heads and am worried about losing quench.

Damon

I ran some calculations for you.

I'm assuming: pistons sitting at a typical .025" in the hole at TDC and a GMPP .028" composition head gasket (6.5cc). Still not great quench, but about as good as you can do without decking the block or resorting to thin steel shim head gaskets.

Assuming that.... you'll need a 22cc dish to hit 9:1. A 27cc dish would be 8.6:1. A 31cc dish (about the biggest you'll find) would be 8.35:1.

Most who have actually measured Vortec heads have found the chambers are actually 62cc, so you'd need piston dishes with 2cc more volume than what I mentioned above to hit the same compression.

Yeah, it's easy to blow compression to the moon with a bigger cube small block.

I beleive a D-dish piston would work best because you can still maintain the quench area, which you can't do with full-face dished pistons.

calebzman

iTrader: (3)

Calc:

http://www.kb-silvolite.com/calc.php?action=comp

F-BIRD'88

It a lot easier to build a low compression blower friendly 350 motor than a 383.
Build it right without compromise and you'll make more power with the 350. Cause you'll be running more boost with less retard.
To find a 383 piston that has a big enough dish to get the cr low enough using 62-64 cc vortec heads will probabily mean a custom piston eg $$(Wiesco, JE, Venolia)$$

TRW makes an off the shelf 22cc d dished Forged pistons for a 350 blower motor. I'd go the 350 route.

F-BIRD'88

You could build it using KB 121 28cc D cup pistons.
Your cr would be 8.54:1 assuming 62cc chambers, felpro gasket and un decked block.

These hyper pistons will live in a supercharged motor
If the top ring end gap is set correctly { that means bigger, a lot bigger than other pistons and a lot bigger than a N/A motor. } You will need a ignition retard box and keep a close watch for detonation.
We're talking a .030"+ ring end gap.

You should be ok to about 8psi boost on 92 octane With spark retard.

If you cannot get your head around all that, build it with custom forged pistons.

Batass

Thanks for the info. I'd like to keep it as close to 9:1 as possible. I'm planning on using a xe282r cam which will bleed off a bit. Probably only use at the most 8 psi of boost too with a vortech. I was hoping to buy a complete balanced 383 kit but with some odd dished pistons, its hard to find one.

formula350sd

iTrader: (2)

Probe has a 20 cc dished piston for 383 and 5.7 rod if you play with head gasket thickness you will be able to come out where you want

84camaroturbo

more boost and less compresion will give you more power then the other way around. i wouldnt go hyper they are just not a good boost piston you can get a wisco forged that is lighter and stronger for about $450 to 500.
i am with f-bird on the 350 if you put a 6-inch rod will help save the bottom end. i run 8.5to1 at 13psi and put 716foot pound of torque to the ground.
it is a vortec 350 e-tec heads studs everywere and meth.

Batass

Extra clearancing has to be done for longer rods right? How do they save the bottom?

84camaroturbo

their is a big artical about rod lenght on ls1tech i will see if i can find it.
it was on a boat forum i found it let me know if it dont work
http://e30m3performance.com/tech_art...atio/index.htm