Rich it’s easy to figure out how many CCs you need to hit a target compression ratio , but without carved in stone CC numbers getting what you have currently for a compression ratio can be frustrating.
Here’s the formula for finding the total CCs you need.
In your motors case a cylinder has 948.9 CCs of volume.
They let’s say you wanted end up with a 10.5 compression ratio .
You then minus 1 from that 10.5 number leaving you 9.5 and then you divide that into your cylinder CCs.
So the result is 99.88 CCs.
Keep in mind that chamber CC volume can change .
If you had CC numbers derived with flat face valves and then swapped over to dish face valves or visa versa that could change you chamber volume by 1.5 to 2 CCs depending on the valves used.
There no substitute for accurately CC ing at least 2 chambers in each head before committing to new pistons.
If you want to have about a 1.2 to 1.5 CC cushion against having too high a compression then do not factor this ring land CC volume into your total CC volume.
This will give you the max compression you could possibly have assuming your other CC numbers are dead on.
__________________
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And he was not talking about 1/8 or 1/4 mile ETs!
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Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
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Last edited by steve25; 11-08-2025 at 07:41 AM.
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