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Simple compression ratio question

  • Thread starter Thread starter 89roadster
  • Start date Start date Apr 1, 2005

89roadster

Founding Member
Apr 19, 1999
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0
Kent Island, MD
Apr 1, 2005
#1
  • Apr 1, 2005
  • #1
I'm in the process of building a new short block that will NA for a few years until I build the car I really want and add a turbo to the engine that I'm building now.

As long as there's not too much wear on the cylinder walls over the next couple years, will I be able to just replace the pistons and rings to acheive a lower compression ratio for the turbo? I know that I'll want a different cam and various top end accessories, but for now I'm mostly concerned about the short block.

I'm currently spec'ing everything out for forged internals in a 331/2 form. Any suggestions on rotating assemblies are appreciated.
 

Rick 91GT

Mustang Master
Nov 29, 1999
9,692
95
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PA
Apr 1, 2005
#2
  • Apr 1, 2005
  • #2
Build it for boost now, the pistons will change from a flat top to a dish and you would need to have it all rebalanced.

A common 4cc flat top on a 331 will get you in the high 10.4-11:1 compression depending on your heads, a 14.2cc dish will get you in the 9-9.5:1 range, or a 22cc would get it even lower.

I was able to go mid 11's with 8.8:1 compression on a 302.
 

89roadster

Founding Member
Apr 19, 1999
1,124
0
0
Kent Island, MD
Apr 1, 2005
#3
  • Apr 1, 2005
  • #3
Rick 91GT said:
Build it for boost now, the pistons will change from a flat top to a dish and you would need to have it all rebalanced.

A common 4cc flat top on a 331 will get you in the high 10.4-11:1 compression depending on your heads, a 14.2cc dish will get you in the 9-9.5:1 range, or a 22cc would get it even lower.

I was able to go mid 11's with 8.8:1 compression on a 302.
Click to expand...
I forgot about the need to rebalance - good point.

The plan is to keep the Thumpers I have.
 

Rick 91GT

Mustang Master
Nov 29, 1999
9,692
95
99
PA
Apr 1, 2005
#4
  • Apr 1, 2005
  • #4
I answered your PM
 
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