Compression woes. What am I missing?
Thread Starter
Staging Lane
Joined: Sep 2014
Posts: 89
Likes: 0
Compression woes. What am I missing? I have used 2 different calculators and come up with 1.38 
which has to be total BS!
Here is what I know:
9.240 Deck Height
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke
What am I missing?
which has to be total BS!Here is what I know:
9.240 Deck Height
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke
What am I missing?
TECH Junkie
Joined: Nov 2013
Posts: 3,913
Likes: 366
From: White Bear, Mn
9.240 Deck Height > I used -0.007 instead
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke > Is this a typo'ed 3.622 or is it really 3.662?
Gasket bore? I'll guess 4.040
With the assumptions above, I get 9.778 static compression. Milling the heads to 63cc (~0.055") will net you about 11.1:1. I'd leave the gasket at .051 since that'll put your quench around .044. You can get a thinner gasket but then you'll be on the bleeding edge of safe quench.
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke > Is this a typo'ed 3.622 or is it really 3.662?
Gasket bore? I'll guess 4.040
With the assumptions above, I get 9.778 static compression. Milling the heads to 63cc (~0.055") will net you about 11.1:1. I'd leave the gasket at .051 since that'll put your quench around .044. You can get a thinner gasket but then you'll be on the bleeding edge of safe quench.
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Staging Lane
Joined: Sep 2014
Posts: 89
Likes: 0
3.662 stroke > Is this a typo'ed 3.622 or is it really 3.662?
Gasket bore? I'll guess 4.040
With the assumptions above, I get 9.778 static compression. Milling the heads to 63cc (~0.055") will net you about 11.1:1. I'd leave the gasket at .051 since that'll put your quench around .044. You can get a thinner gasket but then you'll be on the bleeding edge of safe quench.
Gasket bore? I'll guess 4.040
With the assumptions above, I get 9.778 static compression. Milling the heads to 63cc (~0.055") will net you about 11.1:1. I'd leave the gasket at .051 since that'll put your quench around .044. You can get a thinner gasket but then you'll be on the bleeding edge of safe quench.
Would milling that much cause me to have intake fitment issues?
They are mahle flat tops with valve reliefs. -4cc
I believe by the time I pay to mill these heads, it might be cheaper to pick up a set a used 243's.
Thanks for the input guys.
TECH Junkie
Joined: Nov 2013
Posts: 3,913
Likes: 366
From: White Bear, Mn
Yes it was a typo. Thank you.
Would milling that much cause me to have intake fitment issues?
They are mahle flat tops with valve reliefs. -4cc
I believe by the time I pay to mill these heads, it might be cheaper to pick up a set a used 243's.
Thanks for the input guys.
Would milling that much cause me to have intake fitment issues?
They are mahle flat tops with valve reliefs. -4cc
I believe by the time I pay to mill these heads, it might be cheaper to pick up a set a used 243's.
Thanks for the input guys.
Could have the intake shaved also.
Or just go with the 243's.
Have them milled .020" - .030" and run a .040" head gasket and you will be around 11:1 CR and not have to worry about intake fitment.