I could go that route, but Im still thinking that with the factory 2bbl pistons I will be over camming it.
I was wanting to budget build a sb and still enjoy the cuda(if rain ever stops here LOL)
So I borrowed a dial indicator to help figure out compression ratios on 85 318 stock bore and appears stock pistons. Engine #2 is a 70 318 with .030" over TRW L2373. Heads are 302, not sure on comb chamber volume but I put 60 in. I will CC the heads and looking at milling them what I can without having to change from my stock adjustable valve train. I put 60 CC in there until I get more accurate numbers.
I used verniers to get how far in the hole.
Compression Ratio formula I got from net
Swept Vol +Deck Height Vol + Head Gasket Vol +Combustion Chamber Vol
Divided by Deck Height Vol + Head Gasket Vol + Combustion Chamber Vol
85 318 70 318
Bore 3.91 3.94
Stroke 3.31 3.31
Compression Height 1.72 1.67(DAMMIT!!)
Head gasket thk/vol (1121G) 0.028"/6.1763CC same
Comb chamber volume 60CC 60CC
DeckHeight Volume (averaged) 17.289CC 33.06598CC(OUCH! twice as much)
Swept Volume 651.779CC 661.3164(not looking good lol)
Constant Volume 83.465 99.242
All these numbers give me a comp ratio of 8.8:1 on the 83 318 and a horrible compression ratio of
6.7:1 on the 70 318.
My measuring techniques may be hokey at best, but it gives me an idea as to where I am at and it helps me wrap my head around the “science” of it.
As I mentioned the 302 heads will get cc’d and Im going to ask machine shop the safest amount to mill without having to change from stock adjustable valve train.
Besides being horrible numbers on 70 318, anyone see errors that I may have made? Or numbers I am leaving out?
Thanks all.
Here is link to compression ratio formula
How to Calculate Compression Ratios
