First time attempt. All plugs removed . Engine at ambient temp, 80 degrees today. Screw in fitting and crank engine about 4 or 5 seconds. I am getting these readings:
#2 - 120
# 4. - 152
#6 - 140
#8 150
#1 - 148
#3 146

Still have to do # 5 & 7 but have to leave for an hour and complete later.

Although consistant do these numbers seem right? I was expecting less like maybe 100 to 120?

Seems like a straight forward proceedure and I' m pretty sure I'm doing it right but thought I would throw this out there for any suggestions.

Thanks, jim

 

I'd give #2 another shot, see if you can get closer to the others.

I usually take the throttle spring off the carb and prop the throttle wide open.
Crank until pressure stops rising, maybe 5 or 6 times over.

Keep a battery charger on the battery on 10 amp charge to keep the battery voltage from varying the cranking speed too much.
Look to see that the cylinders are within 10% max of each other.

Your actual PSI will vary with cam specs, temperature, altitude, starter speed and accuracy of your tester.
150ish is probably about right for a stock motor.

 

Yeah, give #2 another chance because the 120 psi could be a fluke. About how many miles do you have on your engine? The 140 to 145 psi would be about right for a stock engine.

 

Thaks. Great points. I realized that the battery was running down and cranking slower. I now have the charger coonected and plan to give each cylinder another test. Especially the 120 psi. Then a wet test and maybe a leakdown test. Hoping that o'riellys has one to loan.

I burned 3 guarts of oil in 2000 miles and about a quart of coolant. Hopefully this is at most head gaskets, which is bad enough. More to follow for more advice.

 

That #2 if it reads the same second time around or nearly so, then try oil in the spark plug hole and do it again. If it then comes up, you just confirmed poor ring seal/worn or possibly broken ring.
Can you tell at what phase of running you are burning oil, evidenced by blue smoke out the exhaust?
1 quart of water could just be a leak somewhere.
How do the plugs look? Is one or more oily and black or have lots of gunk burned on to it? Especially #2.

 

Could be intake gaskets seeping by as well.

Compression test looks ok to me for a stock motor... #2 is a little low but.... Not terribly alarming depending on the miles etc etc. For a stock motor, I certainly wouldn't worry about a single 120 psi compression test.


FWIW, I recently took a road trip in mine, running 3000 rpms on the highway, about 2700 miles, I used 3.5 qts of oil. That's in a 14k mile, professionally built/blue printed big block.

Lots of things can cause oil consumption, but if your plugs aren't showing it and its not smoking, I wouldn't worry too much. However, losing coolant, is not good. If its burning coolant, you likely would see it smoking white/grey smoke. 1 qt of coolant is not much, but it shouldn't be going anywhere unless its puking over into the reservoir, then leaking or over flowing to the ground.

You can get an anti freeze test kit that tests your coolant for hydro carbons, it should tell you if you are getting combustion into the cooling system. If not, then I would look into the intake gaskets leaking and coolant being sucked into the ports. (this however is a long shot)

 

I charged up the battery and kept the battery charger connected and did the compression check again. Sometimes several times on each piston.

DRY
#1 148, 148 #3 146,146,150 #5 140,140,140 #7 158,158

#2 140,145,130,135,120,120

#4 152, 152 $6 140 #8 150, 145, 149 145

WET - squirted some oil in each cylinder.

#1 165, 170, 152 #3 153, 153, 150 #5 150, 150 #7 170, 181

#2 120, 120 ????

#4 150, #6 149, 148 #8 150

The variations in piston #2 are for the most part how long I cranked it. To get the higher number I cranked it about 10 seconds.

So help with my findings: I think everything is OK for an engine with 84 K (has a 3.73 rear end?). cylinder # 2 has a leak but not really that severe? Would you agree?

For further help, here are pictures of the spark plugs I pulled out

















The plug in my hand is from cylinder # 2.

They all appear to look the same. No idea how many miles are on them.

My guess is that the white residue is from leaking coolant?

I filled the radiator full and have traveled a little over 200 miles. The level is now down about 3/4 of an inch.

I never see any blue of black smoke coming from the exhaust. Even at WOT. When I start it cold there is nothing coming out of the exhaust for a short while. After about a minute I see white smoke and some water droplets. If I hold my hand under the exhaust it will become saturated in about 30 seconds. After the engine reaches temperature the exhaust is completely dry. I would think some moisture coming from a cold engine is normal but think what I have is too much and I am in fact leaking coolant.

Do you think a leak down test is in order? Or maybe just a simple pressure test with compressed air to see if and where anything might be leaking that doesn't show up in the compression test?

Thanks for reading all this! Best of all thanks in advance for your input.

 

When I want to pressure test a cooling system I put 10 psi of pressure into it (using my Amflo air pressure regulator) and see if it holds the pressure. You can tee into a heater hose or remove the top 1/2" NPT plug in the water pump and plumb it in there. It should pressure indefinitely.

 

Your engine seems fine to me for a 70"s vintage V8 with that kind of mileage. Ring seal is fading from use which is normal.
My guess is #2 could be carbon on an intake, or exhaust valve since oil in the cylinder had no significant impact on PSI produced. I guess if it were mine I wouldn't worry about it too much.
I might try some kind of top end cleaner in the fuel to see if it improved, or if you felt comfortable with it water down the intake to clean out carbon deposits. However if you still have a catalytic converter in it the water could make things worse for it.

Does your radiator have a recovery system? It sounds like it does not.

If not, then due to normal expansion you are going to puke some fluid out of the radiator at running temps. Then when it cools the level will be lower in the radiator. No way around that without a recovery system.

The plug looks good to me. No real evidence of oil burning. You could just leave it alone.

As far as moisture after starting and warming up, that is normal. Burning water is white smoke. Look for that.