slomarao

iTrader: (6)

I have been getting everthing figured out for my build and have been real busy with work. I ran my numbers into a comprssion calc and came out with 12.2.1?


I have a stock spec 357 build (40 over bore, 3.48 stock crank). The crank has been turned .020, .027 headgasket, .014 milled off the heads (94 casting) no decking or anything done to the block aside the .040 bore. The piston is just as far in the hole as stock.

I thought i would be around 11.6.1 or 11.7.1? any help

gregrob

iTrader: (8)

What piston relief...

kgkern01

iTrader: (10)

Assuming about 5cc volume piston reliefs, stock deck height is usually around .025", you need to know your head cc's. I assume around 53cc being milled .014". You also need to know the bore size on the head gaskets, what gaskets are .027" thick? I know the Impala gaskets are .029" and 4.1" bore and the 1074 Felpro's are .026" thick with 4.125" bore.
So using the folowing:
'assumed' 5.0 cc valve relief volume for pistons
.027" thick, 4.1" bore head gasket
3.48" stroke
.025" deck height
53cc chamber volume

I get an 11.58:1 SCR

gregrob

iTrader: (8)

I always use .034 deck height. Seen a bunch of people say that's where theirs measured. Did you use a 4.060 bore in your calculations?

speed_demon24

iTrader: (6)

Uh....

slomarao

iTrader: (6)

the custom gaskets are 60 over so they dont go into the chamber

gregrob

iTrader: (8)

Uhhh yeah. Whats your point

slomarao

iTrader: (6)

I answered the question, whats your point?

RamAir95TA

iTrader: (2)

LT1 gasket bore sizes are usually 4.100 or 4.125. You shouldn't need a "custom gasket" to prevent them from entering the chamber. Are we all talking about the same thing here?

slomarao

iTrader: (6)

I was on the phone with a summit racing tech, he said this is the way to go for my setup

gregrob

iTrader: (8)

Lol..

RamAir95TA

iTrader: (2)

Oh boy. Have you tried consulting an engine builder, and not a part-time parts guy at an internet wholesaler?

slomarao

iTrader: (6)

thanks for your help guys, really, glad i posted the question

RamAir95TA

iTrader: (2)

We're just trying to clarify what you've got going on that's all. Summit techs don't exactly have the best track record for providing accurate and relevant info in a performance build.

Puck

iTrader: (17)

Your CR will be ~11.4-11.5.

slomarao

iTrader: (6)

THANKS, that is all i was looking for.

speed_demon24

iTrader: (6)

Mine was .015 or .020 i think. It's been awhile but I came up with 11.4-11.5 with a .029 gasket and 53cc chambers.

slomarao

iTrader: (6)

close enough, Ill call it 11.6.1 cuz i have a 027 gasket

RamAir95TA

iTrader: (2)

Agreed...I've seen anywhere from .015" (mine was .020") to .030" on a friend's car (highest I ever saw was .030").