compression question?

[Deep6]

Greetings,

I have a 1984 3.2 Carrera that I am trying to figure the general health of the engine.

The compression test when the engine was cold produced numbers in the low 150's across all 6 cylinders.

Tonight, after 45 minutes of tollway/in-town driving I let the engine cool down for 30 or so minutes and checked the compression and this time the numbers were 175 psi for all cylinders with the exception of #2 which was a low 150.

I am starting to feel comfortable working around a warm engine and am wanting to do a leak-down test.

I want to verify if #2 is a troublemaker.

What determines a warm engine? When should leakdown/compression tests be done?

The car drives smooth and strong at all rpm's but unsure of the mileage since the speedometer has been changed out from a po.

Any advice is welcomed.

George

[Peter Zimmermann]

Do the leak down test cold, it's easier. Here's how:
1. Turn engine by hand to TDC for the suspect cylinder,
2. Remove the spark plug for the suspect cylinder,
3. Insert the hose for the leak down tester into the plug hole, tighten until just snug (let the o-ring do the work),
4. Hook up the gauge to the hose that is in the engine,
5. Connect your air supply hose to the leak down tester,
6. Adjust the inlet air pressure to 80 psi,
7. Read the second gauge; that pressure is the amount that the cylinder is holding,
8. Do the math to determine % of loss. 10% or less is generally considered to be OK.

Do not remove the spark plug before you put the engine on the cylinder that you want to test!

[E Sully]

The numbers look good. I would do an italian tune up to clean carbon out of the engine and then do another compression test. 30 minutes seems ok. Leak down test in combination with compression will give you an idea where the most air is escaping, intake valve, exaust valve, or rings by listening for where the air escapes.
Another thing to check for on a 3.2 is valve guide wear. They have a tendancy to wear out early. Keep track of how many miles you drive before it's down a quart. Does it smoke when you accelerate or slow down? Has the valve clearance been checked regularly? If the valve clearance needs frequent adjustment the guides could be worn.
Also what do the spark plugs look like. Do any look dark from burning oil? Any idea what your gas mileage is?