Thanks for the info..59 sounds too high for me...would want close to stock compression.
And have manley after market pushrods Ponyhtr.

 

Gomer, how the hell did you get compression ratio that high with a factory shortblock and 59cc heads?

 

I was told the 59cc CR on the LS6 59cc heads is 11.2:1. Where is the 11.8:1 coming from?

 

I just ran it thru another online calculator and got 11.5:1. I guess I was wrong on the 11.8, but I thought I had gotten that with a calculator somewhere. I'll find a good online one and post a link to it.

http://www.turbofast.com.au/TFcomp.html Use this calculator. With a piston .007 out of the hole and .042 gasket, I'm getting a little over 11.7 with a 59cc chamber. *on this calculator you have to enter -.007 to let it know that the piston sticks above the deck and is not below the deck. If you enter .007 you will get a lower compression because the calculator figures it as the piston being that far below the deck, you must enter -.007 for the piston above the deck*

 

Can someone please tell me what CR the PP LS6 Style heads with 59cc chambers unmilled on a stock bottom end is. Also, I know the pistons were flycut slightly, but not sure how much.

Thanks

 

If you run the factory head gasket it will give you 11.25 compression.

 

Gomer, I'm not arguing, just want to know why you guys seem to say ".007 out of the hole". The stock stroke + rod + piston compression height nominals = 9.249. The stock deck is quoted as 9.255. That says the piston is .006 down in the hole. Thats .013 diff! .007 out of the hole says the block deck is actually 9.242! Huh? Whazzup?

 

I measured mine at a little over .007 out of the hole the last time I had my heads off. I seem to remember reading a post by Jason from Thunder racing where he said all the ones he'd ever checked was "out of the hole" too. I'll look for some info on it and I'll PM you with it.

Edit: Below is the info I found
Some stock LS1 dimensions per GM:

Stroke: 3.622"
rod length: 6.098"
block deck height: 9.240"
piston comp. height: 1.338"

piston to deck ht.= block deck ht. - [(stroke/2)+ rod lenght + piston comp. ht.]

9.240" - [(3.622"/2) + 6.098" + 1.338"] = -.007"

So the piston sticks up .007" above the block. The negative sign denotes the piston is above the block. Most conventional engines have the piston slightly below the block deck and would have positive piston to deck heights.

 

Looks like patriot has 59cc and 64cc and 72 cc.So 64 cc should be close to stock compression and 72 woudl take it down to what 9 or 9.5? That should be good with forced induction I guess.

 

I calculated about 11.1 with the 59cc, the 64cc is a great option for the people wanting close to stock compression, the 64cc chamber is actually a LS6 chamber