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Contributed by c.d.iesel
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Thursday, 16 February 2006 |
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How to perform a compression test?
ALUMINUM HEADS? loosen the spark plugs when cold,
and snug up to warm up the motor
remove all the plugs
battery must be fully charged and starter motor
spinning like mad
disconnect your ignition primary - even more
important if you have a HugeBox-o-Transistor mega-spark system
also for all of you with powered
fuel pumps and injection systems - de-power yer pumps
so the possibility of FIRE is eliminated!!
hold the throttle fully open during cranking
valve clearance should have been adjusted first- COLD -
only crank each tested cylinder 4 revolutions
record each of the 4 pulse readings of each of the 4 revolutions
the 1st pulse of the needle should be more than 1/2 of the 4th pulse
for example, if 185 is the target:
30-60-90-120= there's a leak all the time and uniform in size like
a burnt valve, or severly burned out head gasket
90-100-110-120 = that cylinder is sealing up to a point
but begins to leak - rings, leaking head gasket....
120-145-165-185 = is normal
adding a little oil to a weak cylinder and re testing will only show
some sealing by the rings - but indicate a direction to look
...next proceed to the Cylinder Leak Test
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