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Re: Compression Testing
[Re: emarine01]
#552836
12/13/09 06:59 PM
12/13/09 06:59 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Quote:
Seeking some opinions on the proper way to interpret compression tests, How many pulses do you count? Example/ my small block hits 200 on the third pulse cold, my sons jeep hits 90 on the 3rd and 130 after 10 pulses cold, is it how fast it builds or the max psi that counts?
Whats most important is that you do all holes the same - and the same every time you do the test. My standard is: Hold the primary throttle blades open ( I use the return spring and always leave myself a note taped to the steering wheel regarding this -  ). Remove all plugs. I do 5 pumps for each hole W/ eng. warm. After the first 4 holes, I will put a charger on the battery for a short, just to make sure the cranking speed is the same for the last 4 holes. I like to look at the reading after the first pump. If it is low compared to the others, it is often an indicator of a weak hole that the final reading ( after 5 pumps ) might not show as much. It can also indicate scoring / leakage on the cylinder wall near the bottom of the stroke. Don't trying to compare different engines. The closer the final ( after 5 pumps ) readings are the better. Cam manufacturers these days often give suggested dynamic Cylinder pressures for their grinds. If you can get that info, your numbers should fall with in their spec. If a weak hole is indicated, a leak down test should be performed next. I never liked to squirt oil in the hole to see if the leak was valves or rings. Too "gray" of a test for me.
Fastest 300
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