Sizzle Chest

iTrader: (5)

Im running TFS 225s with 65 cc chambers on a stock internal LQ4 and want to mill them down to between 10.8 or 10.9 to 1 with a stock head gasket. Im getting a lot of conflicting information on the internet which is preventing me from feeling real confident with the compression ratio calculators.

I know the bore and stroke but I've seen wide ranging stats for chamber cc on stock 317s (70-74cc) and piston dish volume. Anybody a real authority on the subject? I'd like to be able to fill in these blanks:

63 cc = ? cr
62 cc = ? cr
61 cc = ? cr
60 cc = ? cr
59 cc = ? cr

Im thinking I need to go down to 59cc which would require milling .036 off (assuming .006 = 1 cc) to even get close to 10.8 to 1 but others are saying 61cc (.025) will get me there. So I'm really confused at this point. Thanks for any input .

Michael Halo

i'll like to know where 65cc head will put me on my LQ9????

Sizzle Chest

iTrader: (5)

I'm pulling my hair out already on this and there you go introducing different pistons into the mix....

Sizzle Chest

iTrader: (5)

This is what I get.

62 cc = 10.35:1 (would need to mill .018 off current 65 cc chanber)
61 cc = 10.47:1 (mill .024)
60 cc = 10.59:1 (mill .030)
59 cc = 10.70:1 (mill .036)

I'm using the following inputs into a compression ratio calculator:

bore 4.0
stroke 3.622
chamber size 71cc (stock)
piston dish -7.5 (plugged this value to get to stock cr of 9.4:1)
gasket thickness .05 (stock)
piston deck clearance 0

These inputs get me to 9.4:1 which is the stock cr on a lq4. From there I just played with different chamber ccs. Anyone see any flaws in what I am doing here?