[Josh69]

Ok, thought I had a rear seal leak, took engine out, found the freeze plug missing behind the camshaft. Gone entirely. The cam may be walking. The dist gear looks fine, the mechanical fuel pump was still working. Can the cam walk that far and the engine still be running?

I called my carb builder, and he thought the oil out the carb was due to 'reverb', basically blowing oil out the intake valve. I'm not sure where the oil would be from, maybe valve seals are leaking but they were just done as well and it didn't burn any oil, no smoke or burnt oil smell from exhaust. If the timing is that far off, it could be explained by the cam walking. Otherwise, the car ran pretty good. I have a PCV hooked up to the carb base plate. I thought the oil was coming from the valley pan, but it seemed too convenient for it to be leaking from exactly the center of the valley pan on both sides....then I noticed oil hanging off the throttle shafts on the sides of the baseplate, and my fuel log was covered in oil. I drove the car a few times about 5-10 miles each trip trying to isolate the oil leak from the rear, during these drives, no oil came out the carb area, this just happend on the last trip and would spray out the side of the carb under acceleration (I don't have a hood on the car yet). So the carb leak is recent, compared to the rear cam cover leak.

I plan on removing the valley pan and front cover to inspect for damage or wear, but I figured the cam would be pretty much locked in place by the eccentric/bolt assembly, and if they failed, would the timing chain allow enough movement, and if so, wouldn't the dist gear stop it? It would have to move a good 1/2" to pop that freeze plug out!

[Josh69]

How far into the block does that plug get pressed? I can see a slight step up about 1/4" into the block. The cam is about a half inch from the back of the block, just guesstimating. Maybe the cam did walk enough to push the plug into the larger diameter opening and allowed it to fall out, or maybe the builder just didn't press it in far enough?

My valve covers are simple Edelbrock stamped units with no baffles, so maybe my PCV was sucking the oil into the carb and that is what caused it to run out the throttle shafts. It was definitely more prominent in the rear shaft closest to the vacuum port.

[Mr. P-Body]

Josh,

Since this is not a Chevy engine, it has a cam retainer plate. The cam CAN'T "walk" like it can in a Chevy. The plug should be installed to where there's about 1/8-1/4" between the back of the block and the plug. The plug will "slip" in to the step you refered to. It must be tapped beyond that, but use the outer edge to tap on, not the center. Apply a small film of Permatex "Aviation" around the inside of the hole before you put the plug in.

I can't sy WHAT the oil in the carb is about...

Jim

[Josh69]

My carb builder is a chevy guy, so maybe that's why he thought it could happen. I recall the retainer plate, and I spoke to Ace at PPR, he concurred that it would be impossible for it to walk as long as that plate was still intact. My dist and mech fuel pump would have been affected as well I would presume. I'm guessing my machine shop didn't press the plug all the way into that step.

Now, to figure out why the oil came out of the carb on the last drive. Could enough oil be drawn into the carb to cause that type of scenario? Or is it possible that there is some reversion going on? I could think the timing would have to be significantly off for that to happen.

[67post]

What do you have for breathers? You should have at least 1 vented cap on one side. The other can be sealed. It is possible that what you are seeing is oil vapor/blowby that is looking for an escape route, and the pcv line is the only option. Even a brand new engine with good ring seal will generate a small ammount of crankcase pressure. This may be the source of the oil you see.

[Josh69]

Good news, I found the issue. In my pursuit of eliminating all leaks, I over-tightened the aluminum valley pan and it pulled up on the sides, about 3/16". So it was just spraying onto the sides of the carb. I forgot I did that a few weeks ago and hadn't driven until this happened.

So, since my cam didn't walk and I don't have the blowbye I thought (no sign of oil in the breathers, etc.), I'm just a freeze plug, a few gaskets and RTV away from a trip to the dyno room....

Even with using a small mirror, etc. I wasn't able to see that pulled away from the sides of the heads due to the thickness of the manifold until I had it out on the hoist....so I guess that is a lesson learned!