First do compression dry test then maybe wet test.
|COMPRESSION TEST |
Disconnect the "BAT." terminal from the HEI distributor or ignition module.
To determine if the valves or pistons are at fault, a test should be made to determine the cylinder compression pressure. When checking cylinder compression, the throttle and choke should be open, all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should not be less than 70% of the highest and no cylinder reading should be less than 689 kPa (100 PSI).
This should be done with four "puffs" per cylinder.
Normal - Compression builds up quickly and evenly to specified compression on each cylinder.
Piston Rings - Compression low on first stroke, tends to build up on following strokes, but does not reach normal. Improves considerably with addition of oil.
Valves - Low on first stroke, does not tend to build up on following strokes. Does not improve much with addition of oil.
[For wet testing] Use approximately three squirts from a plunger type oiler.
Closer the numbers the better. Many books allow 15-20psi range for top cyl to bottom cyl.Percentage Change
To get close to "normal" compression specs... (I think) 15 x compression ratio (V6=8.9, L4=9) − 15.
15 is close to Absolute(atmospheric) pressure at Sea Level. Real values depend on local weather and altitude.
− 15 is because most gauges do not use Absolute pressure. They zero at normal atmospheric pressures.
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[This message has been edited by theogre (edited 04-20-2015).]