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lbc_newbie
Jedi Warrior
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Anyone know how to do this? I'm looking at a motor that is not installed, yet the owner claims only 25K miles...how can I check compression?
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compression check on uninstalled engine? How?
- Thread starter lbc_newbie
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Jim_Gruber
Yoda
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Use a car battery, jumper cables, Google Leak Down Tester. You can make one for $25-30. Gauge $10 or so at HF or was it Pep Boys. One of those. Need a few more parts and pieces.
Westfield_XI
Jedi Warrior
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Short of pulling the plugs and hooking up the starter to some jumper cables, you are left with the leak-down test that your mechanic performed on your old engine. Have the seller put this engine in the back of a pick-up and take it to a good shop. They can hook it up in the bed of the truck to the air system in a few minutes and tell you if there are any problems. In an earlier post you said your mechanic told you it leaked at the intake, breather and the exhaust, is that correct? If so then your old engine needs valves as well as rings. I am surprised that the PO would spend to install a 210 gearbox into a car with a bad cylinder, are you sure that they did a leakdown check or did they just do a standard "crank it and pump it" type pressure test.
The leakdown test is much more useful for diagnosis since it uses an external air source to pressurize the cylinder, this allows you to listen at the carbs, the tailpipe, the valve cover and the breather for hissing air. This will not give you a maximum psi of each cylinder, but will show the difference between the supply air pressure and the pressure the cylinder will maintain. To make it easy to compare from engine to engine most people use 100psi as the supply pressure: a good race engine should hold 97% or 97psi, an elderly street engine can get down around 75% and still run smoothly albeit down on power.
The leakdown test is much more useful for diagnosis since it uses an external air source to pressurize the cylinder, this allows you to listen at the carbs, the tailpipe, the valve cover and the breather for hissing air. This will not give you a maximum psi of each cylinder, but will show the difference between the supply air pressure and the pressure the cylinder will maintain. To make it easy to compare from engine to engine most people use 100psi as the supply pressure: a good race engine should hold 97% or 97psi, an elderly street engine can get down around 75% and still run smoothly albeit down on power.