stock heads are 58cc on fbodies and i heard vettes had 54cc. piston velve reliefs are 5cc i believe. the ony thing i see wrong with the speed pro's is they're $50 each and thats $400 anyways for a set and I dont believe they 2618 either. I know for the same price you can get 2618 probe or keith black dished pistons around 20cc. That brings it down to a choice of better alloy pistons for the same price.

 

I've been running 15psi on a regular basis over the last two yrs and 10 psi for 2 years before that. My car is a daily driver that gets beat on every day. The Speed Pro's are built like tanks. My compression ratio is 9.2 to 1 with heavily bowl ported stock heads. Not sure what alloy they are (and dont care) but if you look at the pictures on summit you'll see the meaty ring lands.

My stock lt1 aluminum heads were 54cc but were worked to around 58cc with some good bowl porting

 

do you know witch speed pro piston your useing? what the dish cc was? thanks

 

try these: 2618 alloy and around the same price with a decent sized dish:
http://www.cnc-motorsports.com/produ...39&CtgID=12723
obviously you'll want .030" over if you're boring, or these will work for a standard 4" bore
i believe these will put you around 9:1 with standard bore and deckheight, or try the smaller dish for a little more compression

 

See post #14....Its a -20 dish.

 

ok so im thinking kb part #9913-030 6.4cc dish should bring my cr to about 9.9-1 with a 60cc head i was alittle unsure what what to put for deck hight to i put .025 head gaskets say there 8.7 felpro 1074 hows all this look? thanks for your time guys. can wait to get this thing back on the street! got it from my dad blown head gastket (and piston but didnt know) and have only driven it some 80 miles

 

i see there 2 pistons from kb all the same but one has a deck hight of 1.265 in. and one have a deck hight of 1.565 what would the affect on cr be?

 

i believe one is for a stroker 383 and one is for 355. and stock deck height is roughly
.025" unless you mill some off the block.

 

paxtonLT1,

These numbers would be your piston compression distance. Essentially from pin centerline to piston deck. When you run a different stroke or different rod length, this number will change. It has to because you have a fixed block deck height you are trying to 'package' this into. The stock block deck height for our LT1 or SBC is 9.025". If you increase stroke or rod length, then the pin MUST move up higher in the piston. If it didn't, then the top of the piston would pop out of the top of the block - it wouldn't work. So if you go from a 3.48 crank to a 3.75 the pin needs to move higher in the piston and your compression distance gets smaller.

The 6.4cc relief piston is a 'flat top' piston - not a dished piston per se. Assuming a FP 1074 (4.060" bore diameter and 0.039" compressed thickness) your compression with a piston deck 0.025" in the hole, 60cc chamber, with a 3.48" stroke is 10.10 , or 10.81 with a 3.75" stroke

http://www.csgnetwork.com/compcalc.html

Why not put a forged 'dished' piston in there? You aren't going to lose much of any driveabilty, throttle response, etc, going from 10:1 to 9:1 or ever 8.5:1. What you will do with a 'boost-friendly' SCR is reduce risk of detonation which will kill a boosted motor. Especially running pump fuel which varies in quality tank to tank.

-Scott.

 

google 'compression ratio calculator'