Minnesotajeff

Hey guys,

I have a 1972 Cutlass with a 455. 62,000 original miles, it’s never been out or apart. I pulled the motor today to clean it up and reseal it, as I have some oil leaks. Figured it was a good winter project to keep me out of the saloons.

I knew the oil filter mount gasket was leaking badly and that the exhaust manifold had to come off to replace that so that was the biggest reason to pull the motor. It’s getting a new exhaust system when it all goes back in.

so, a few questions:

I had also figured the back of the intake manifold was leaking because i installed an edelbrock last winter and I’ve noticed oil coming down the back of the motor. But once out and on the stand, that looks fine. But it appears that the rear sides of both head gaskets could be leaking oil. Is that possible? All cylinders have good compression, even with all the others. It runs perfectly. But right at the line where the heads meet the block it is wet with oil from there and down. I hadn't planned to pull the heads and would rather not. This was going to be a simple reseal. What are your thoughts? Replace the head gaskets?

I was also suspecting and expecting to see. Leaky rear main seal. I was planning to replace it with the Ford 460 2 piece rubber seal. But upon inspection it is all dry around it. Should I leave it alone or replace it and risk creating a leak?

besides resealing it the only thing I’m planning is to replace the timing chain and gear set.

thanks for your help

Minnesotajeff

I went back out to look at the back of the motor again. I just can’t believe that oil would be leaking out of just the back sides of the head gaskets. There isn’t any oil under pressure passing through the head gaskets, is there? I’m not expert, but I’ve rebuilt a few engines and understand them........ wouldn’t there just be drain holes for oil to drain back into the valley area? It sure looks like they are leaking, but it must be something else.........

Sugar Bear

Head gaskets should not be leaking oil, probably run-off from other leaks. Replacing the head gaskets will cost/lower compression ratio as replacements are thicker. Consider doing valve seals while it is apart. About the rear main, that is a tough call...dry is dry. My vote is leave it alone.

Good luck!!!

Vintage Chief

Well, I had oil leaking from the back of my 350 after I meticulously replaced the intake manifold gasket. I continued to wipe it down to find where my oil was coming from - it wasn’t a lot, but it was driving me nuts. Turns out there was no seal under the distributor. I didn’t need to remove the distributor to R&R the intake manifold gasket. I then pulled the distributor and that fuzzy wuzzy oil dampener sponge was shot as well. At this point I suspected oil was migrating out of the distributor shaft. I rebuilt the distributor and that solved the oil leak from the back of the engine. Maybe have a look at that distributor seal?

Minnesotajeff

Good idea Norm air flow under the hood and around the firewall can do some strange things with oil and coolant leaks. I was beat after getting the motor out so after getting it on the stand I called it a day. I’ll inspect the distributor tomorrow

Vintage Chief

Sorry, maybe I wasn’t very clear. That seal under the distributor at the lock down plate - there wasn’t even one there in mine, which there is supposed to be. Probably rotted away after many years. Then that like fiberglass sponge filter on the distributor shaft itself was shot as well as cracks and holes in the thin plastic ring which surrounds the distributor shaft.

don71

I wouldn't pull the heads, should be no reason to do so by your description. I think you have a good plan so far concerning the timing chain. When you pull the front cover off, get a good look into the pan and decide if you need to remove/clean it too. Hopefully, no nylon chunks in there but its possible, and the oil pump pick up screen too. Its worth mentioning, because I've found things in old neglected engines at the bottom of pans. Again, your engine doesn't seem to be in that state of dis-repair.

One more thing. If you do see chunks of nylon in the pan also consider they might be plastic valve seal pieces. They'll look like just like the nylon chunks from a timing chain so give that some consideration too.

Vintage Chief

And, before you go stir-crazy grab a small bottle of UV/fluorescent dye, add to oil and view w/ a black light. Automotive parts stores carry the dye and generally sell small penlight black light flashlights. You'll readily find this leak.

Run to Rund

I'd be suspicious of the rear rubber intake manifold seal. If leaking, spray clean with solvent, seal with black RTV. Second possibility is valve cover gaskets.

geardoc66

Oil does pass through the head gasket here, albeit not under pressure. This is the drain back from the valve area to the intake valley. If I recall correctly, there is a small ledge that the oil can collect on that never completely drains. It is possible for a leak to occur here, but it is not very common.

OLDSter Ralph

I am with you here. I would suspect the valve cover first and the rear of the intake manifold second.

I think that area you have circled was embossed to "crush" and seal on the rear of the head, when the heads were torqued.