Oliver super 77 compression... Need help???

56oliver · Mar 1, 2015

does anyone out there know what the compression in p.s.i. Should be on a super 77 also, to do the test I assume I should leave all 6 plugs out and the throttle open all the way?

Thanks

John B. · Mar 1, 2015

Yes the throttle should be full-open and all the
plugs out. What kind of compression do you have
now? If any of them are much lower than the others
squirt some oil in the cylinder and see if it
changes the compression, if it does then the
piston rings are worn. If the oil doesn't raise
the compression reading then the valves are
leaking.

JOCCO · Mar 1, 2015

I would do all cylinders wet or dry. your choice AND SEE IF THEY ARE EQUAL in pounds. What I look for (in a quick assessment) is: one of more cylinder way off Example 1-5 130lbs #6 75lbs There lies your problem. IF You do not know what it has for pistons and so on its hard to say it should have 175lbs etc. If its been setting for years oil in cylinder will probably bring it up. DO NOT GET TO TECHNICAL JUST SEE WHAT YOU GOT.

old · Mar 1, 2015

I am not 100% sure but I think it should be in the 125-150 range as for PSI

MARK ROBKE · Mar 1, 2015

All plugs out,throttle open,choke open,good cranking battery.As jocco says look for more equal readings rather than a specific reading, and if any are low,squirt 2 squirts of engine oil in the hole and a crank again.If it raises,rings are worn,if not,valves or head gasket.Crank til highest reading usually 3 or 4 revs. But I would expect at least 120 psi.Mark

billfromwisconsin · Mar 1, 2015

an engine will run with any compression of about 75#
tired engine 100#
as other say 125-150 is great
I was taught dry, 4 compression cycles, throttle closed, choke open. I like to leave other plugs in when I do so I can listen to sound balance, balance is most important, 10-15#

56oliver · Mar 1, 2015

Thanks guys that really helps

Dick L · Mar 1, 2015

That was the way I was instructed in the 1950's. Throttle being open or closed might give a higher or lower reading one way or the other. I wouldn't know for sure but it would have no affect on the evenness of the cylinder pressures. Just something to haggle about like my dad is stronger than yours.

^D

Wayne in MN · Mar 1, 2015

Throttle MUST be open all the way or the engine will not get all the air possible to compress for an accurate compression reading. Can you breathe very well with your hand over your mouth?
Count the same number of compression strokes for each cylinder.
Re-test with a few squirts of engine oil in each cylinder.
Don't run the battery down or the slower speed of the piston will give inaccurate readings.

Oliver super 77 compression... Need help???

56oliver

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John B.

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JOCCO

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old

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MARK ROBKE

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billfromwisconsin

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56oliver

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Dick L

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Wayne in MN

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