I'll be doing the same thing this winter. I'm thinking about a 383 stroker.
which cr ??
Thread Starter
Instructor
Joined: Feb 2003
Posts: 229
Likes: 0
From: east coat SAUDIA
which cr ??
i'm going to forged the engine ,but i still dont have a clear idea a bout which piston and head. what is the good compression ratio for high hp and 14 psi. with p1 procharger.
* flat top piston -8.6cc with stage 3 ls6 heads. = 8.6:1
* flat top piston -2cc with stage 3 ls6 heads. = 9.1:1
my goal is 600 wrhp .
what do you advice me ?
* flat top piston -8.6cc with stage 3 ls6 heads. = 8.6:1
* flat top piston -2cc with stage 3 ls6 heads. = 9.1:1
my goal is 600 wrhp .
what do you advice me ?
Burning Brakes
Joined: Dec 2004
Posts: 1,117
Likes: 0
From: New England
Originally Posted by MRC5
i'm going to forged the engine ,but i still dont have a clear idea a bout which piston and head. what is the good compression ratio for high hp and 14 psi. with p1 procharger.
* flat top piston -8.6cc with stage 3 ls6 heads. = 8.6:1
* flat top piston -2cc with stage 3 ls6 heads. = 9.1:1
my goal is 600 wrhp .
what do you advice me ?
* flat top piston -8.6cc with stage 3 ls6 heads. = 8.6:1
* flat top piston -2cc with stage 3 ls6 heads. = 9.1:1
my goal is 600 wrhp .
what do you advice me ?
I'll assume you are using 72cc heads, .045 HG, and coming out of the hole .005" (just basic assumptions). Based on these numbers you'll have about 9.1:1 CR using the -8.6cc piston. With the second -2cc piston you'll have about 9.75 :1 CR.
Given the 2 choices, go with the -8.6cc combo.
Melting Slicks
Joined: Jun 2002
Posts: 3,060
Likes: 3
From: Dublin CA
LS6 heads have 64.5cc chambers. http://www.smokemup.com/tech/ls1.php
Keep in mind most forged pistons are only rated to 15psi boost. At least get the pistons ceramic thermal coated to keep heat out of the piston. Mahle pistons come coated, in some cases coating is a $300 option.
I'd recommend 9.1:1 CR as you'll have trouble getting enough boost from the P1SC.
Keep in mind most forged pistons are only rated to 15psi boost. At least get the pistons ceramic thermal coated to keep heat out of the piston. Mahle pistons come coated, in some cases coating is a $300 option.
I'd recommend 9.1:1 CR as you'll have trouble getting enough boost from the P1SC.
Last edited by blu00rdstr; Sep 13, 2005 at 09:54 PM.
Melting Slicks
Joined: Jun 2002
Posts: 3,060
Likes: 3
From: Dublin CA
Originally Posted by FRC Tom
Al. heads don't like much more than 12:1 CR.
With a CR of 8.6 and 14 lbs of boost you are looking at a ECR of 12.017:1.
With a CR of 8.6 and 14 lbs of boost you are looking at a ECR of 12.017:1.
Burning Brakes
Joined: May 2000
Posts: 881
Likes: 0
From: Clearwater, FL, USA
Originally Posted by blu00rdstr
You know, I never did understand how to calculate the whole ECR thing when factoring in lopey cams.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
Burning Brakes
Joined: Dec 2004
Posts: 1,117
Likes: 0
From: New England
Originally Posted by blu00rdstr
LS6 heads have 64.5cc chambers.
Keep in mind most forged pistons are only rated to 15psi boost. At least get the pistons ceramic thermal coated to keep heat out of the piston. Mahle pistons come coated, in some cases coating is a $300 option.
Keep in mind most forged pistons are only rated to 15psi boost. At least get the pistons ceramic thermal coated to keep heat out of the piston. Mahle pistons come coated, in some cases coating is a $300 option.
BTW, I could be wrong about this but I don't think Mahle pistons are 'fully' coated. I believe they only come with an anti-friction coating on the skirt (which is somewhat common with performance pistons). I do not believe they have any type of thermal barrier of the face.
Thread Starter
Instructor
Joined: Feb 2003
Posts: 229
Likes: 0
From: east coat SAUDIA
thanks ya all for replys..
patirot 6 liter heads stage 3 72 cc with -2 dimond piston ..= close to 9.2:1 .. i thing this compression ration is good for p1 .
http://www.c5frc.com/calculators/Com...Calculator.htm
patirot 6 liter heads stage 3 72 cc with -2 dimond piston ..= close to 9.2:1 .. i thing this compression ration is good for p1 .
http://www.c5frc.com/calculators/Com...Calculator.htm
Burning Brakes
Joined: Dec 2004
Posts: 1,117
Likes: 0
From: New England
Originally Posted by MRC5
thanks ya all for replys..
patirot 6 liter heads stage 3 72 cc with -2 dimond piston ..= close to 9.2:1 .. i thing this compression ration is good for p1 .
http://www.c5frc.com/calculators/Com...Calculator.htm
patirot 6 liter heads stage 3 72 cc with -2 dimond piston ..= close to 9.2:1 .. i thing this compression ration is good for p1 .
http://www.c5frc.com/calculators/Com...Calculator.htm
Based on the piston coming out of the hole .006" and using your .055" HG with the -2cc piston you get 9.47:1, 9.67:1 with the .045 HG.
Drifting
Joined: Aug 2004
Posts: 1,898
Likes: 0
Originally Posted by mdhmi
With that setup I would try to get the CR around 9.5:1.
Haven't found a complaint yet with the AFR 205 heads.
Mark
Haven't found a complaint yet with the AFR 205 heads.
Mark
should leave some com for instant grrrrr on the street .. ya !!! you can't run as much boost but it's tuff getting 1000 hp down to the ground anyway 
Le Mans Master
Joined: Sep 2000
Posts: 6,976
Likes: 527
From: Clouds Over California
Originally Posted by SS930
Your calculator is flawed. It doesn't allow you enter a negitive number for the deck height. The LS1 pistion typically comes out of the hole about .006", you can't enter this in your calculator. Also, most HG are about .045", but some are .055".
Based on the piston coming out of the hole .006" and using your .055" HG with the -2cc piston you get 9.47:1, 9.67:1 with the .045 HG.
Based on the piston coming out of the hole .006" and using your .055" HG with the -2cc piston you get 9.47:1, 9.67:1 with the .045 HG.
He's right. You either have to subtract it from the HG or using another CR calculator..besides Ross
Oh and by the way, I have used the same setup for 3 different power adders now (SC, TTi, and PTK).
I utilize -2cc valve reliefs, and use the CC volume to reduce compression ratio...with a pinch of extra HG thickness (Cometic MLS .065"). It has been a good recipe so far.
My heads are LS6 77cc (West Coast Cylinder Heads..A&As guy). I could have used GM MLS HGs (.054" compressed) and my CR would have been 9.2:1..but went with a slightly thicker HG (my deck height is .014"..due to 6.126" Lunati Rods and Diamond Piston Combo..oh and the block was decked .004"). So my CR is 8.94:1. Going strong...at least this morning it was.
Nice thing about using flat tops with valve releifs is that if you ever want take everything back off...all you need to do is swap the heads for some stock ones and your back to your stock CR....approximately.
Last edited by Shinobi'sZ; Sep 14, 2005 at 03:31 PM.