Compression numbers
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Junior User
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compression question
What is the general compression range of a mid-time chevy 350? My brother and I are argueing that his 137 psi average is low, he says NOT. What would a new motor run? We took out all 8 plugs and then did an average. He thinks his lack of power is due to something else, maybe rocks in his head. 
Thanks
Thanks
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Junior User
Joined: Nov 2004
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Compression numbers
I'm in an arguement with my brother about the reason for his lack of power in his suburban. It is a chevy 350. His average compression # 137. I say it's low, he says it's mid-time. What is new? What is mid-time, and what is worn out? Thanks
Senior User
Joined: Oct 2004
Posts: 304
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From: Colorado
Well compression ratio for stock piston stock 76cc headed chevy 350 is 8.5:1.
137 PSI per hole was that a warm reading or cold? A fresh engine with factory ring gap @ operating temp will be 200 PSI+. So what your getting if the pressure was taken cold is a good engine, if it was taken @ temp it's still a good engine well above spec.
Whats the engine doing, just lack of power, how much lack of power?
137 PSI per hole was that a warm reading or cold? A fresh engine with factory ring gap @ operating temp will be 200 PSI+. So what your getting if the pressure was taken cold is a good engine, if it was taken @ temp it's still a good engine well above spec.
Whats the engine doing, just lack of power, how much lack of power?
Postmaster
Joined: Mar 2003
Posts: 4,038
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From: Spokane WA
perhaps his lack of power comes from the fact that thats a LOT of weight for a 350 to move around.
you picked a weird forum to put this question in.......
Compression readings have a lot to do with the CR of the motor, which we dont know, so its hard to say if they are low or high, but they arent too bad, consistency is more important, is that a dry compression test I assume as opposed to a wet test?
you picked a weird forum to put this question in.......
Compression readings have a lot to do with the CR of the motor, which we dont know, so its hard to say if they are low or high, but they arent too bad, consistency is more important, is that a dry compression test I assume as opposed to a wet test?
Posting Legend
Joined: Sep 2001
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Moved to General Automotive, threads merged. Non Ford engines are not covered in the Ford truck tech forums.
Last edited by Torque1st; Mar 27, 2005 at 03:38 AM.
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Posting Guru
Joined: Jun 1999
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From: Everett, Wa
Well if static compression ratio is 8.5 then you would have around 156 PSI new. This is according to EA v3.0
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