67 oil leak

[David G.]

Looking at 67 327/300 hp for sale. Dripping motor oil (not trans fluid) from joint between transmission and bell housing? Probable cause and expense/difficulty to repair? Car runs and drive great but probably less than 500 miles in last 8 yrs Thanks

[Timothy B.]

Re: 67 oil leak

David,

I would start with the simple things first like the steel valve covers. The covers are difficult to seal in the lower corners because they flex unlike the aluminum covers. If the engine makes high oil pressure there could be a leak at the rear main seal or oil pan gasket.

Try tightening the oil pan, how much oil does it leave on the ground?

IMO, the 327/300hp is a nice engine for street use.

[Duke W.]

Re: 67 oil leak

It could be as simple as the oil drain plug gasket, or it could be the rear crankshaft seal, which can be changed with the engine in the car, but not always successfully.

If the car is otherwise okay, I would not let the oil leak stop you from purchasing. It's common on these vintage cars, and sometimes the easiest thing to do is leave a drip pan under the car while it's in the garage and just live with it.

Don't tighten the oil pan bolts beyond the CSM spec. Overtightening can excessively crush the gasket and make any leak worse or start a new one.

Remove the bell housing inspection plate and with a mirror, observe the front side of the flywheel. If it's dry, the rear main seal is okay. This seal is often indicted, but is often innocent. Since the engine is installed with about three degrees tilt to the rear, oil from small leaks will tend to migrate along the pan rail to the back of the engine and accumulate until there's enough for a drop to form and fall.

Finding leaks is best accomplishing by thoroughly removing all oil residue and dirt from the engine, then carefully inspecting for new oil residue as you accumulate miles. You can also add a dye to the oil, which will show any oil leaks using a "black light".

Duke

[David G.]

Re: 67 oil leak

Thanks Tim

[David G.]

Re: 67 oil leak

Thanks Duke. I thought worst case it was rear crank seal but didn't know if that could be fixed w/o pulling motor

[Michael J.]

Re: 67 oil leak

Even if the worst case, rear main seal, it can be fixed. I had my L71 rear main seal replaced without pulling the engine, some mechanics have done it many times with the Chevy V8s, since it is so common. BTW, it is the most common thing to have happen in all the Chevy V8s, they are very bad about that. Good luck.

[Joe L.]

Re: 67 oil leak

Thanks Duke. I thought worst case it was rear crank seal but didn't know if that could be fixed w/o pulling motor

David------


The real main oil seal can definitely be replaced without removing the engine from the car. In fact, it's a fairly easy job. Several things to keep in mind if this becomes necessary:

1) Use only seal GM #10121044 or Fel-Pro #2912;

2) Apply sealer to the rear bearing cap EXACTLY as instructed and diagrammed in the factory service manual;

3) If there is any damage whatsoever to the seal journal on the crankshaft (e.g. grooving, roughness, nicks, dings, etc.), then you must obtain a special seal with a displaced lip. If the damage extends to the entire width of the journal, then the crankshaft needs to come out and be replaced or machined.

[Bob H.]

Re: 67 oil leak

Duke

500 miles in 8 years. If it is the rear main, is there any oil additive that might soften up the seals?

[Michael M.]

Re: 67 oil leak

I agree with Joe Lucia and recommend the Fel-Pro 2912 rear main seal. Don’t let anyone talk you into using the Fel-Pro 2900. The 2912 is more expensive, but it’s a fluoroelastomer (brownish in color) compared to the 2900, which is silicone and blue in color.

My ’67 300HP developed a rear main seal leak shortly after I bought it. The previous owner had used a reputable engine builder and the engine had less than 2,000 miles (and four years) on it. I pulled out a leaking Fel-Pro 2900 that showed no evidence of faulty installation, except the parting line of the seal wasn’t offset from the parting line of the main cap as recommended by Fel-Pro.

I replaced the seal myself, using a Fel-Pro 2912, without an issue even though it had been 40 years since I had been inside a Chevy engine. It’s been totally dry for a year now. Just follow instructions and be sure to use the installation tool. The pic below shows half of a blue 2900 on the left and the 2912 on the right.

[David G.]

Re: 67 oil leak

Sorry guys. Out for couple days. I appreciate the feedback. My local mechanic told me engine had to come out and then it was iffy if leak could be stopped

[Bob H.]

Re: 67 oil leak

David:

I think you need a different mechanic. Sounds like he doesn't want to deal with it.

Bob

[Joe L.]

Re: 67 oil leak

Sorry guys. Out for couple days. I appreciate the feedback. My local mechanic told me engine had to come out and then it was iffy if leak could be stopped

David-----


If he knows the engine has to come out, then he must also know what's causing the leak. So, what is it?

Otherwise, is he saying that the only way to determine what's causing the leak is to remove the engine and then find out? If so, that's absurd. Except in cases of an egregious problem, it will be near-impossible to determine what the leak source is after the engine is removed. At that point, all one can do is "attack" all the things that could reasonably cause a leak and hope for the best. Then, put the engine back in the car and see if it leaks? If it does, what does one do then----pull the engine out again and start all over?