I just had my cylinder heads reworked and I reinstalled them myself. The car was running great, but there was a nasty oil leak from the back of the engine. I figured I had not put enough gasket goop on the back part of the intake so I pulled it to reseal it. Well, it does not look like the oil was leaking from the intake. Instead I noticed what looks like an exposed bolt hole or oil gally that is on top of the block, driver's side, and half covered by the head. I don't know what that hole is but I assume it is the source of my leak.

What is that hole? Why is it half exposed? Is it the source of my oil leak? If so, what do I do about it? I have no idea what it is. Is it possible to put the heads on the wrong side of the engine? I had zero problems reinstalling everything and all gaskets and bolts lined up perrfectly. The car runs great, aside from running rich. What's the deal!!!!!

 

Could be the hole for the oilpressure sending unit, but don't know why it'd be 1/2 covered by the head?

Also, doesn't matter which head goes on which side

 

No, it's on top of the block, as in on the deck where the cylinder head mounts.

I don't even want to think about what kind of oil mess would have been made if I left he oil pressure sending unit off!

 

OMG!!!! It is a pressurized oil hole, it's left over from the drilling of the passage that goes from the straight vertical passage that terminates in the OPSU place, to meet with the rear cam bearing.

You can't put a plug in that hole with the head installed. Guess what you have to do.....

 

WTF! Why is it just now leaking? I didn't do anything to the block and I sure as hell didn't remove any oil plugs.

What happens if I fill that space full of gasket maker?

 

If it's leaking via oil pressure, it will not hold.

Even though it's a small seep, once it fills it's cavity, the pressure will eventually become equal to your oil pressure and push the sealer out of the way.

 

I don't know, I got on top of the engine and looked inside there and I don't think that it's a source for oil. I tried sticking a wire down there but it did not go anywhere. I can't see my head gaskets allowing that much oil to leak. The gaskets look clean all over the rest of the engine. I can't see how I could have done something so drastically wrong on the back of the head gasket.

Is there some source of oil back there that I may not be thinking of? Could I have pinched something while I was working on the heads? I'm not that bad a mechanic. I mean, I should be able to install some heads and an intake without creating a Kuwaiti oil well! I'm just going to resinstall the intake and run the car over to the car wash and pressure wash the back of the engine. I'll climb up inside there to see if I can spot a source after that.

On the good news side, my Torq Thrust II's arrived today.

 

I had the same problem when I started my rebilt 355. I also thought I left the plug out and took the head off and it was installed correctly so I put everything back together and the leak stopped. I think it was the combination of a bad seal at the rear of the intake and the dist. not clamped down tight enuf. I hope you are using RTV on your intake end rails and not those rubber gaskets because thos are a leak waiting to happen. Good luck.

 

Thanks. I hope the problem is that I didn't use enough RTV on the back of the intake. I saw one spot where it looked like it might have been kind of thin. I didn't pull the head, so if that's where it's leaking then it is going to continue to leak. I'm willing to put the intake back on and risk having to take if off again in order to avoid taking the head(s) off unnecessarily. I'm going to put the intake back on tomorrow and see how things shake out.

 

I am also assuming the valve cover gasket is sitting right in the valve cover. I have seen that happen before too.

 

Yeah, that part's all good.

 

Distributor gasket??

 

Might've been. I have it all together and so far it looks dry. I put some RTV on the distributor gasket this time and put some extra torque on the bolt holding it in. I lost the original bolt and had to use a substitute of a slightly different length. I think there was more room for tightening on this bolt.

Anyway, it looks like it might be fixed. I'll keep my fingers crossed. Thanks for all of your input, guys.

 

hmm I have a mysterious oil leak in the back of my engine, its not the valve covers, intake, distributor, etc... Its not the rear main and its not the oil press. sending unit...

but oil just appears all over the place in the rear of the engine. it drips down the sides and onto the ground constantly.


Where is this oil hole you guys are talking about? its not in the block but its in the... ?

 

It's on the deck surface of the block, driver's side, about 1" from the intake mating flange of the block, and about 1/2" from the rear edge of the deck. It's 1/8" pipe.

A mystery oil leak on the back of the motor is more likely to be the welch plug at the rear of the cam bore.

 

<b>the welch plug at the rear of the cam bore.</b>

Thats one of those "mini freeze plugs" isnt it?

I was wondering what those were for.

 

There are 3 small plugs back there, usually threaded pipe plugs, that plug the passages that run from the front to the rear of the block parallel to the cam bore. Those could leak.

The one I was referring to is the 2-15/16" or whatever it is one that plugs the cam bore itself. That plug has drainback holes behind it, but if the rear cam bearing is put in carelessly, it could block them, and then there'd be full oil pressure on the back of that huge plug.... 60 psi on a 2 sq in thing, it wouldn't stand much of a chance for long.