compression test 440ex

[JOHNDOE83]

i did a compression test and it says i have 165psi. i was wondering what other 440s tested at? if you know what your compression test reads let me know.

[GPracer2500]

FWIW, my old 416 pumped 175psi cold at 1300ft with a stg 2 HC (old version). Gauge was checked against several others so it was known to be within 5lbs or so.

what range should a stock bore and stock piston have in a compression test. My brother and I are both getting one done within the next week to see about rebuilds.

[GPracer2500]

Originally posted by FoxHondaRider
what range should a stock bore and stock piston have in a compression test. My brother and I are both getting one done within the next week to see about rebuilds.

100-128psi. But realize that figure takes into account the auto decompresser doing it's thing. That number can't really be compared to numbers from builds not using the auto decomp.

Originally posted by GPracer2500
100-128psi. But realize that figure takes into account the auto decompresser doing it's thing. That number can't really be compared to numbers from builds not using the auto decomp.

So when I get it compression tested with all the OEM engine parts and all nothing taken out or changed I should get a reading between 100 and 128PSI? If its below 100PSI I need a new piston and rings or just rings?

[JOHNDOE83]

Originally posted by GPracer2500
FWIW, my old 416 pumped 175psi cold at 1300ft with a stg 2 HC (old version). Gauge was checked against several others so it was known to be within 5lbs or so.



was that a high compression piston like 11:1 or 12:1

[GPracer2500]

Originally posted by JOHNDOE83
was that a high compression piston like 11:1 or 12:1

It was a JE 10.8:1. Head and base gaskets were purchased off the shelf from a local shop. I couldn't say if the were exactly stock EX thickness. The head may have been XR400 thickness and the base may have been laser cut from a sheet (this shop makes some gaskets from blank gasket sheets). Or, they may have been normal thickness. I didn't even think to measure them at the time (dumb).

What piston, gaskets, and cam are you running? What's your elevation?

[JOHNDOE83]

dont know what piston it is but its deffinetly a 440. the gaskets are weisco 440 gaskets, the cam is stage 2 hotcam and im in florida at sea level.

[GPracer2500]

Originally posted by FoxHondaRider
So when I get it compression tested with all the OEM engine parts and all nothing taken out or changed I should get a reading between 100 and 128PSI? If its below 100PSI I need a new piston and rings or just rings?

Yes, you should get between 100 and 128. If it's low it could be a ring sealing problem or a valve sealing problem. I'd say in most cases it's probably worn rings but there are a number of things that can cause low compression.

There's not really a good way to tell if the cylinder and piston are still in spec without removing them and having a machine shop measure them. If the cylinder and/or piston are out of round or otherwise out of spec then just installing rings alone isn't the answer.