[4dblnkldude]

My friend and I recently built and installed a chevy 406 in his 71 nova, and about 10 minutes into break in there was an oil leak. It is on the driver head near the booster, coming right out of the corner. It is right by the last oil return hole in the head. We let it cool and I held a rag back there and finished the break in, and the oil does not leak at idle. This is the first engine he or I have built. The oil pressure is 65 at 2200 and 43 at idle, the engine has dart heads and was decked. How could this oil be leaking between them with two head bolts right there? Any help is appriciated!

[Lightfoot]

Not sure where you mean exactly. Is it from the seam between the head and block?

Is it squirting, as in pressurized, or just running down? I'm not sure how it could get from the rocker area out through the head gasket, unless there is a fine crack in the corner of the head.
I hope it isn't a compromised head gasket.

[Lemans64]

Did u use sealer on the intake ends or did u use the rubber gaskets on the ends?? Did u put some sealer up the end of the intake gasket between the intake and head. It's possible u have oil leaking from the meeting surface where the head, block and intake manifold all meet. The oil would then follow the head gasket and drip off the lowest part, ie the lower back corner.

Rick

[Malibu]

I was thinking the back of the intake myself. Just like mentioned above I do not use the skinny rubber gaskets for the front or back of the intake. Instead a use a bead a sealant and pay special attention to the corners.

Sometimes the use of crappy cheap aftemarket valve covers can cause leaks too.

Also verify no oil pressure gauge nylon lines aren't causing the leak.

[4dblnkldude]

The leak is actually coming from where the head meets the block, down by the exhaust port. Its coming from nowhere near the intake. It is not pressurized, just running out. I think it may have something to do with the head gasket that was used. The gasket was .058 compressed, a bit thick, so I geuss we'll try retorqing first, and if the heads need to come off then so be it. Thanks for your replies.

[sleepy]

The head gasket has nothing to do with sealing oil except at the intake front and back in the corners. Head gaskets would leak water. heads would leak water. valve covers would leak oil.intake valley gaskets would leak oil. intake to head would leak water. The only way you can get oil from a head gasket is from the bolts under the valve cover and if that's where it's coming from you have a water leak too.

[Lemans64]

As previously stated, oil leaking form sbc head gasket is very rare, only a drain back to pan is used in the sbc head, no oil pressure feed through head gasket is used. most likely culprit is intake or valve cover gaskets, Intake end seal will follow head gasket to back exhaust port. Use a mirror to inspect after cleaning and running at some rpm to verify.

[4dblnkldude]

Well we fired it up on friday afternoon and cleaned the whole area where the oil was leaking. Apparently it is leaking from a pressure tap type plug halfway under the head surface. I looked at another block and its a 1/4 inch square plug, similar to the one on our motors by the distributor. Its not a really bad leak, so we cleaned it again with brakleen and filled it in with rtv. Not a permanent fix but at least it will drive into the garage instead of pushing it. Now we'll just have to find some time to take the head off. Thanks again!

[tnsmith10]

ill bet the leak is up near the corner of the block almost where the head and intake meet. its actually under the head. i just had to fix the same leak on my car. heres a pic

oops, missed the last post. looks like you found it... sorry

[ITSBACK]

I had a small block in my GTO when I bought it and had the same leak. It was that square bolt. I think that is for an oil pressure line for a mechanical gauge. I removed it and put a new 1/4-20 bolt in it and it stopped.

[goatwgn]

You are not the first nor the last person this as happened to. I have seen it about 10 times, and had it happened to myself once, helping a friend of mine put a sb400 in a 76 Camaro. I hadnt installed the distributor yet, and I saw light from a droplight shining through this hole at the top of the lh rear of the block at the deck surface. The machine shop was supposed to install a plug there and didnt. I learned to always double check after machine shops. I have seen cam bearings with the holes not lined up, freeze plugs knocked into blocks (rattling around),and even oil gallery plugs missing.