I bought an 86 Camaro running a little rough and with a slight knocking sound. I checked compression and found:

1-97
2-185
3-180
4-180
5-86
6-180
7-167
8-180

I added oil to cylinder 1 and 5 and got:

1-100
5-90

When I started taking it apart I found cylinder 5's plug with a lot of built up carbon and the post on the distributor missing. (I'm hoping that was the slight knock)



I don't see anything around cylinder 1 on the block, head gasket or head that looks like a leak or any other reason for low compression. Cylinder 5 looks good other than the carbon build up on the valves.

Is there anything else I should check before I pull the pistons and replace rings?

Also, how hard (if possible) would it be to pull the oil pan with the motor in the car?

Thanks in advance for any help.

 

If adding oil didn't improve the results, that indicates a valve sealing problem or head gasket leak. When adding oil improves that results, then its considered a ring problem.

 

It might have the rockers over adjusted, or carbon on the valves, or it might need a valve job.

 

It looks like 1, 5 and 7 are suspect. They're all on the same bank.

Your oil squirt test points to valves. But before you do anything, I'd pull the valve cover and take a look there.

 

Tear the motor down. If the reason for the damage has been identified and repaired, that doesn't change the mechanical damage that has already been done as a result of that.

 

Adjusting the valves didn't change anything. I've got some old heads off a 350. When I get a chance I'll throw them on and see if I get anything better.

 

if squirting oil improves the compression reading then the rings are worn/damaged.
rent or borrow a bore scope and take a peek into the cylinders with the low compression readings.

Otherwise do a leak down test on the two holes with low compression... if you hear air in the crankcase this will confirm the problem is related to the rings / pistons / cylinder walls.

air coming out the exhaust pipe.. the exhaust valves

air coming out the intake manifold.. the intake valves


Do a coolant pressure test to confirm the head gaskets are not bad, but if the car runs and not burning white smoke the head gaskets are probably fine.


at this point it makes no difference, the motor will have to come out and apart to repair so all new gaskets will be on the list of parts.

 

I had that head off before my first post. I don't have an air compressor so I couldn't do a leak down test. The cylinder walls look good to me. Nearly no ridge at the top and the cross hatching looks good.

 

im gonna guess your probably is gonna be burnt valves, head gasket would show low compression on adjacent cylinders and the wet compression test shows the rings aren't your problem

 

only way to know for sure really is take it apart or cylinder leakage though

 

Get a pressure tester from your local parts store. Then using the tester, hook it to an air source. Make sure both valves are closed and pressurize the cylinder. If you hear noise through the intake....it's the intake valve. Vise versa for the exhaust valve.

I'm thinking you over adjusted the valves.

 

I have a compression tester that I could use but I have no air supply. I lossened the valves until there was play in the pushrod and still didn't have compression.

Hopefully I can find the time today to put that other head on and see what the compression looks like.

 

That won't work, you need the valves to open to draw in air to compress.
New cars that have cylinder deactivation turn off the valve action to save mpg.

 

That seems obvious after reading it.. lol

I believe I had them adjusted right before I did that though.

I put the 350 head on and got

1-45
3-120
5-60
7-130

So I guess it is a ring issue. Maybe I didn't get enough oil into the cylinder when I tried that test. (it was a pain to get any in)

I'll probably just put it back together with the 305 head and run it while I rebuild a 2 bolt 350 block I have in the garage.