I picked up a running 73 /6 that the owner said runs but, he didn't know the history of the car. The odometer said 36K and the seats and pedals didn't look worn. He removed for a SB install. I bought it complete for the PS,AC conversion in my 64 D100. I did a compression test with plugs out, throttle open and cylinders dry. It hit 90-100psi first stroke and 150psi after 5 or 6. Is this a valid test or does the engine really need to be operating temperature?

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I'm going to attempt to fix this project and not make it any worse.

That's fine in my humble opinion.....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

for that kind of compression test, you're just seeing if the rings and valves are seated well, valve timing is correct. The test is usually done with 4-6 cranks until the pressure reads constant/builds to maximum on your gauge.

If you have a low psi reading on a cylinder, or just want to compare, some people say you can squirt a shot of oil in the cylinder to compare with dry result, if your rings and all are good, you shouldn't see too much difference with and without oil shot. If you see a huge difference, then maybe your rings are leaking more than they should.

150 psi sounds like a healthy engine compression number - you're good.

Brian

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A more thorough diagnostic is a leak down test, where you apply compressed air to the cylinder (static test, valves closed, at TDC compression stroke) and evaluate not only the rate of air loss from the cylinder but also where the air loss is occurring, e.g. blown head gasket, rings, valves. This test requires a tester and a compressed air source. If you're not having any problems, burning oil, oil in coolant, excessive water in exhaust, then you don't have to run a leak down as well.

brian

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