Broken ZZ 383

[Edgardoug]

Shooting 150 hp of NOS (plus a detonation event) I blew a piston of my ZZ 383. This crate engine got hyperetectic pistons ... I knew they were the weak link among this engine internals. Now I want to step up and install a good set of forged pistons. But it turns out GMPP installed a "Special" stroke crank shaft with a stroke of 3.800 (not the common 3.750). Where can I find pistons to go with this crank? Rods are 5.700 Edgardoug.

[BLOCKMAN]

Originally Posted by Edgardoug

Shooting 150 hp of NOS (plus a detonation event) I blew a piston of my ZZ 383. This crate engine got hyperetectic pistons ... I knew they were the weak link among this engine internals.

Now I want to step up and install a good set of forged pistons. But it turns out GMPP installed a "Special" stroke crank shaft with a stroke of 3.800 (not the common 3.750). Where can I find pistons to go with this crank? Rods are 5.700

Edgardoug.

Your probably looking at a custom piston for the stroke combontion.

[427Hotrod]

Or some regular *383* pistons. They are for a .050" shorter stroke. Your pistons are likely .020-.025 down in the hole anyway.....maybe use 383 ones and mill the tops a little to end up with .000-.010 OUT of the hole. Then use typical .040 or so gasket to end up with really nice quench with no need for block decking.

Check compression heights...you'll also find that many replacement pistons are *short* anyway to allow for decking and you might find what you need with careful measuring.

JIM

[billla]

Custom pistons aren't all that much more expensive than "off the shelf" any more with CNC machining. With many companies you can even say "I want a piston like P/N xxxxx, but with a compression height of 1.375". Talk to your machine shop; they've got books for miles and smarts to see if there's anything off the shelf - or to tell you who they'd prefer to order the customs from. Remember - your shop has to make them work; don't walk in with a box of pistons and say "here".

I tend to stick a little short of a zero deck, but I'm a conservative builder. You do want to shoot for that magic .045 quench since you're doing all this work. IMHO I would not take a huge deck cut when you can get the right deck height in the pistons. Cutting the deck significantly will cause problems with intake alignment. You'll need to get the intake cut for sure...and you'll definitely want to look at the port alignment as well if you go that way.

I agree it's kind of an odd approach for GMPP - I understand wanting to keep a 4.00 bore (new block) but why not stick with a "standard" 3.75 stroke and just give up the lousy *6* cubes???