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16 valve vibration (leak down test) explained please read



I did it i did the dreaded 
(leak down test)
Ill explain for those that dont know it.
leakdown tester threads into sparkplug hole
and you plug air hose from air compressor on other end
their is 2 gauges one for psi you regulate in by adjustment knob on tester
other gauge tell you how much air is leaking past intake valve
or exhaust valve or the dreaded rings/piston.
both valves must be closed for testing leak down test.
top dead center cy#1 and cy#3 turn engine 180 degrees cy#2 and cy#4
if gages are = or les then 15% leak down your are good
its when pressure input gauge is 90psi and output gauge is 60psi
their is a 30% leakdown (thats my problem) that means air is leaking past 
a mechanicle part rings,valves        
you listen to oil fill in valve cover and if you hear air it passing through it  
it is the rings.
If air is comming out tailpipe its an exhaust valve.
air body or carburator its an intake valve 
and yes it is bad news
I did a compression test first cy#1 150psi cy#2 175psi cy#3 150psi cy#4 175psi
cylinder 1 and 3 were low by 25 psi that is why I did a leakdown test.
I know a lot of you dont have tools to do a leakdown test
but I thought some would like to know about it
see if I gessed and said it was a valve problem  I would do a valve job
and it would not fix problem. (alot of time and money spent for nothing.)
The only fix would be a rebuild or ring replacement and the time to Remove, take apart
clean assemble and install you should go all the way rebuild start all new 
if you have the money . $$$$$$$$$
cy#1 and cy#3 leak down 30% pass rings must be cracked
thats my vibration 
two cylinders that are bad in a row in the fireing order
vibration comes and goes because sometimes rings move 
back together giving engine more compression

                       john.delaney
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