Ford Mustang Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
326 Posts
Discussion Starter #1
Building a 347 engine with probe's low comp 8.5:1 pistons. That is figured with a 61cc head- what would my compression ratio go to with a 58cc Canfield head?
I know there are other variables when figuring compression ratio, but I am trying to get a ballpark figure
Thanks!
 

·
Registered
Joined
·
401 Posts

·
Registered
Joined
·
326 Posts
Discussion Starter #3
Thanks for your help. I would like to use the compression calculation from the link, but I don't know what the piston cc is (dish of the piston) and I already bolted on the heads. I tried calling Probe, but I guess they have 3 different types of 8.5:1 pistons, so they don;t know. I don;t remember the serial number on them anymore either. I have to get a chip burned for them so I guess I will go with 8.75:1.
 

·
Registered
Joined
·
238 Posts
302" = 4949ccs = 618.6ccs/cyl
8.5 = (618.6 + chamber vol) / chamber vol
therefore 8.5 * chamber vol = 618.6 + chamber vol
therefore 7.5 * chamber vol = 618.6
therefore chamber vol = 82.48 cc's.

Reducing chamber vol by 3ccs for the new head, then recalculate:

CR = (618.6 + 79.48) = 79.48

So the answer is CR=8.78. With a 306 the number is 8.799.. so still 8.78.

- Steve
 

·
Registered
Joined
·
326 Posts
Discussion Starter #6
Cool. This is for a 347 engine though, how do I re do the calculation for that? (Math is not my forte).
Thanks
 
1 - 9 of 9 Posts
Top