low compression on cylinder 6

[BryanDyer]

ok guys so I did a compression test last night
all cylinders were between 180-190
I did 8 turnovers on each cylinder, Wot, cps unplugged
but 6 I only had 119 psi
so I went ahead and did a wet compression on that cylinder, added a cap full of oil turne it over to get the oil spread then tested
it only went up to 130 psi so this is only an 11 psi increase
is this significant enough to be the piston rings? or does it sound like a valve? I was going to do a leak down test but if like to know if it's the head or block first

 

[IndigoMKII]

ok guys so I did a compression test last night
all cylinders were between 180-190
I did 8 turnovers on each cylinder, Wot, cps unplugged
but 6 I only had 119 psi
so I went ahead and did a wet compression on that cylinder, added a cap full of oil turne it over to get the oil spread then tested
it only went up to 130 psi so this is only an 11 psi increase
is this significant enough to be the piston rings? or does it sound like a valve? I was going to do a leak down test but if like to know if it's the head or block first

On the airplanes I've done where we used a compressor fitting to pressurize the cylinders, if it was the rings you can hear it in the dip stick tube whereas if it was the valves you could hear it in the exhaust/intake. If you do pressurize the cylinder make sure you put a breaker bar on the crank and slowly increase the PSI into the cylinder.

Also, did you test the compression on a warm engine?

 

[BryanDyer]

no the engine is not running right now...
1 reason I did a compression..

 

[BryanDyer]

I just don't know is that was enough jump in psi to be the rings or not

 

[OfnaRcR4]

Could be, wuldn't know until you pressurise it.

 

[BryanDyer]

I've never actually done a leak down as I have never had to
so could you explain step by step exactly what to do?
I know I need a fitting and need to pressurize the cylinder and listen in the exhaust/intake and I guess dipstick
how much air do I put in though? just need an explanation

 

[hvyman]

What kind of hg?

No 6 is 1 of the most common cylinders for a bhg.

Can also do a leak down test to see whether its rings/hg/ or valves.

 

[IndigoMKII]

I've never actually done a leak down as I have never had to
so could you explain step by step exactly what to do?
I know I need a fitting and need to pressurize the cylinder and listen in the exhaust/intake and I guess dipstick
how much air do I put in though? just need an explanation

I normally put in anywhere from 80-100 PSI. Like I said earlier, make sure to feed it on slowly so you don't turn the engine over.

 

[BryanDyer]

What kind of hg?

No 6 is 1 of the most common cylinders for a bhg.

Can also do a leak down test to see whether its rings/hg/ or valves.

cometic mhg with arps
only 3000 miles on the hg