New rebuild, low compression.

G

goodcar

Senior Member
Have put a little over 100 miles on rebuilt engine with Snyder 5.5 head, runs ok but compression test shows 60-65 psi. Squirted oil in cylinders, now get 75-80. All readings taken cold, expect would probably be a little better if taken when hot. Block was rebored .040 over, new pistons and rings. Should I expect compression to get better with more miles or do I have some other problem?? Thanks for any suggestions.
 
The compression readings indicate the rings may not have seated yet. Give it another 100 or so miles and check again.
 
x2 with John.

Yes, with a 5.5 you should have a little more compression.

Don't forget that the throttle should be wide open for the test.
 
old31 said:
x2 with John.

Yes, with a 5.5 you should have a little more compression.

Don't forget that the throttle should be wide open for the test.
Click to expand...

Hate to admit my ignorance but opening the throttle fixed the problem. Thanks guys.
 
Did you get moly or iron rings?
If moly they can take more than a thousand miles to seat.
Iron less than 1000
5.5 head should give you 100 psi without adding oil
 
gustafson said:
Did you get moly or iron rings?
If moly they can take more than a thousand miles to seat.
Iron less than 1000
5.5 head should give you 100 psi without adding oil
Click to expand...

Don't know if iron or moly. Got them from Snyders catalog no. A-6149-040
Hastings.
 
Just drive it & quit wearing out the spark plug THREADS!---You can't hurry the natural break in. It'll be alright!
Bill W.
 
BILL WILLIAMSON said:
Chief said, "When you're always FUSSIN' with a good running car, you're just LOOKIN' fer TROUBLE"!
Bill W.
Click to expand...

Done fussin with the engine runs great. Now movin on to fussin with the transmission, jumps out of 3rd gear when slowing down. Rebuilt from one of the top vendors. Don't think driving is going to fix this problem.
 
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