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Generation III Internal Engine
1997-2006 LS1 | LS6
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Old 04-27-2011, 08:02 AM   #1
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Default Piston Compression Height vs Piston Deck Clearance

By looking at the formulas for calculating those two values, it's obvious that they depend on each other:

Piston Compression Height = Block Length - (Stroke of Engine/2 + Rod Length) - Deck Clearance

Example: 9.245 - (3.622 / 2 + 6.098) - (-0.007) = 1.329

I couldn't reach the formula for calculating piston deck clearance but by looking at required parameters in the calculator on this link, it's obvious that the piston compression height is required to calculate piston deck clearance.

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


My question is: is there a formula for calculating any of those two values without referring to the other one?

I have seen a calculator on this link but I don't think that I can reach some of the values they are asking for

http://www.rbracing-rsr.com/squishcalc1.html

Thank you
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Old 04-27-2011, 10:50 AM   #2
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Which two values are you wanting to calculate? It is really a simple equation, which can be altered to calculate any of the variables in the equation, but you really have to know all but one variable for it to be effective. You cannot calculate needed rod length without deck height, stroke, and compression distance. You cannot calculate desired deck height without stroke, rod length, and compression distance.
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Old 04-27-2011, 12:32 PM   #3
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I know that I can use the same formula to calaulate both values but that's if I know one of them but my problem is that I niether know my piston compression height nor I know my piston deck clearance and I need a formula to calculate onne of them without referring to the other.

All what I know about the engine I bought is that it's a 383 engine with Mahle 3.905 dish pistons with -6cc and eagle rods that are 6.125 inches long.
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Old 04-27-2011, 12:49 PM   #4
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That is likely Mahle's LS1105905I06 piston set, unless you ordered something custom. It will be a 1.105" compression distance, which puts your piston zer deck at 9.230". Your actual block deck height will vary and would have to be measured by a machine shop. OR you could use a bridge tool and measure how far the piston is in the hole, from which you can derive your block's deck height.
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Old 04-27-2011, 01:14 PM   #5
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Quote:
Originally Posted by Samer View Post
I know that I can use the same formula to calaulate both values but that's if I know one of them but my problem is that I niether know my piston compression height nor I know my piston deck clearance and I need a formula to calculate onne of them without referring to the other.
You can't. Those variables are dependent on eachother. You have to determine one to find the other.
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Old 04-27-2011, 01:37 PM   #6
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Thank you Matt for the helpfull information.
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Old 04-27-2011, 01:42 PM   #7
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So, according to your estimate calculations and assuming that the LS1 deck height is 9.24, that puts my pistons 0.01 in the hole, isn't it?
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Old 04-27-2011, 02:26 PM   #8
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That is correct, assuming your block deck height is a true 9.240".
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Old 09-28-2014, 07:55 PM   #9
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My question is if I go from a stock rod length of 6.098 to a new rod length of 6.125 how do I determine my comp height? Whats stock comp height on a Ls1?

What I have so far is that if I change out to a 6.125 rod length that my comp height should be 1.314 and mahle makes a piston of that comp height and bore I need.

My question is that correct I just stumbled across a rod chart but want to be 100% sure.

Thanks
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Old 09-28-2014, 07:55 PM
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