Compression 71-454
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Instructor
Joined: Nov 2012
Posts: 124
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Compression 71-454
I decided to check my compression while I replaced plugs. Numbers are
# 1- 135. # 2- 137
# 3- 138. # 4- 142
# 5- 150. # 6- 150
# 7- 138. # 8- 140
This was a dry test engine cranked 4-6 times each.
Are these normal numbers?
Thanks
# 1- 135. # 2- 137
# 3- 138. # 4- 142
# 5- 150. # 6- 150
# 7- 138. # 8- 140
This was a dry test engine cranked 4-6 times each.
Are these normal numbers?
Thanks
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Numbers are all within reasonable range of each other. I'm assuming that the engine has significant miles on it. If you don't have any blow-by after start-up or when you punch it, keep it maintained well and 'keep on cruising'. 
Thread Starter
Instructor
Joined: Nov 2012
Posts: 124
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Mileage is over 100k. Motor has been rebuilt by previous owner but appears to have been run hard. It does smoke some.
Last edited by ftf396; May 16, 2016 at 11:24 AM.
Thread Starter
Instructor
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Race Director
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From: Plano TX
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
160psi is the 'factory new' baseline number for the 365hp 454; 150psi for the 425hp 454.
For an engine with 100K miles on it, cylinders that make 85% of 'factory new' expectation (135psi) is not all that bad. Piston rings wear; bores wear out-of-round; valves have burnt/distorted areas where they originally sealed well.
I'm still of the opinion that if the OP is OK with engine function and performance, there is no immediate reason to rebuild that engine.
For an engine with 100K miles on it, cylinders that make 85% of 'factory new' expectation (135psi) is not all that bad. Piston rings wear; bores wear out-of-round; valves have burnt/distorted areas where they originally sealed well.
I'm still of the opinion that if the OP is OK with engine function and performance, there is no immediate reason to rebuild that engine.