How much compression should a 420a have new??

[nitrokid]

How much compression would a new 420a be able to make and what would 225 psi of compression be considered..good, great, excellent, or just decent.

 

[rstare]

210psi is the factory compression rating. 190-220psi is normal, however.

 

[nitrokid]

the reason i ask i did a compression test on my engine and i got 220,220,215,225
and it sounded good to me but i wanted to see how close to factory specs it was cause it
has 150.000 miles on it

 

[rstare]

With those numbers, I would assume you have a pretty new, rebuilt engine. And probably bored .020 over.

 

[slo952g]

last i checked it was between 170 and 240. i have 90k on my engine and it is at 180 all across.

 

[Locke]

the reason i ask i did a compression test on my engine and i got 220,220,215,225
and it sounded good to me but i wanted to see how close to factory specs it was cause it
has 150.000 miles on it

Give it a Seafoam (or MCCC) treatment and see if the numbers come down a tad.

 

[nitrokid]

well i have put a new headgasket n it but thats the only thing new on the engine that would affect compression but the guy that sold it to me might had done sone engine wold but when i had the haed off change the head gasket every thing looked stock

 

[Jeff99GS]

Did you have the head milled when the gasket was changed?

Its probably just a little carbon build up on the valves. Seafoam it like Locke said.

The numbers are all close together so that is GOOD.