[Cardo]

Anyone ever have an oil leak here? Do you think a light bead of rtv would take care of it? Anyone?

[Cardo]

Like this?

[Cardo]

This one too.

[hal101]

it does not look good to me
maby you need a a linebore

[HWYSTR455]

Those caps need to be fitted, period. They're going to walk. Have the caps trued and the block line bored, or you'll be asking for trouble. If it's out of the car and on the stand now, take care of it now, otherwise it'll be more trouble, headache, and work later...

[quick67bird]

From what I understand main caps should have no space beneath them. If there is a space and you have a correct torque reading then the caps are binding on something. You should not have to use the main cap bolts to pull the caps down, but they should be flush with the block.

Robert

[61-63]

Irrespective of the need to have the block aligned bored or whatever, the '61, '62, '63, and '64 PMD chassis books, the years I have, all say to run a line of sealant from the rope seal to the outer edge of the saddle to where the pan gasket goes. Therefore Pontiac did anticipate the possibility of oil leaking under that saddle.

[HWYSTR455]

61-63 - True on the sealant, but if there's a gap between the block & cap, it will trail out of there towards the back, unless you squeeze the rtv into it. Also, the bead should really only go from about the cap dowel back or so, where the pan/cap/block interface.

[Cardo]

I believe that this (rtv bead) is the route i'm going to go. This motor has about 8000 miles on it since the bottom end was put together. The crank and main bearings were in good shape and the cap fits tight on the dowels and the other side is tight. The pics were taken with no bearing and no rear main seal installed. This motor has run for the last 40 years like this, and not wipe out a crank yet... it's just that i've had the car on the road for the last 6 trying to figure out why it leaks oil, but not all the time. This has got to be it, third try, third rear main seal, and none of them probably leaked. Thanks 61-63 for the tip. I have a 63 manual that i will check out before i finish this up. This motor is actually my 389 out of my 66, but i do believe this this answer is what would apply in this case. I can't see spending that much money on this after my above reasoning. If this were an all out race motor with rpm's in the stratosphere, then i could agree with the align hone, but that was also checked at the inital rebuild, and found to be okay. I've got a feeling that somewhere over the past 40 yrs, that cap was dropped on the floor. Thanks all for the advice.

[BVR421]

your pics make it appear to be all screwed up as the caps are not sitting flush with the block surface, hence the confusion about what/where is leaking oil.
If your feeler gauge is actually going under the bearing cap when the bolts are tight then no amount of sealer will stop a massive oil flow. I assume you just placed the caps loosely on the block to take the picure of that area?

[Jack Gifford]

If you follow the Pontiac shop manual instructions EXACTLY, there will be no leaks in that area:
"Before installing rear main bearing cap, apply a 1/16" bead of sealer on face of rear main bearing cap from seal groove to external cork groove on both sides. (Use crankshaft sealer Permatex No.3)"

[Cardo]

I agree Pontiac Jack. In the pics the main cap is torqued but there is no bearing or seal installed... i was checking for interference. The pic with the RTV oozing out is as assembled and is the way i will be leaving it. As i stated earlier this block/cap has been like this for 40 years and hasn't come apart yet. I guess i get the village idiot award because i never caught that line in the manual about the sealer. I checked my '66 shop manual today and it does indeed call for a bead of sealer. Again, thanks to all who responded, and thanks for pointing out the obvious which i should have seen. The sealer stays.

[Geoff]

The fact that you can insert a feeler gauge THERE is puzzling. Both the cap & the block in that area are large chunks of machined cast iron that should bolt up with no gap. Have you checked for any burrs?

[Cardo]

Yes I checked for burrs on both the cap and block, in the hole in the cap, nothing. In all of the pics the feeler gauge is a .0015 gauge and is pushed in as far as i could get it to go. I've had this car for almost 9 years and it has always leaked oil out the back of the motor. This is the 3rd time i've pulled the motor for an oil leak at the rear main seal(?) once with a rope seal and the second time i put in the BOP seal. After the second time i let the car run in the driveway for over an hour and not a drop of oil. Took it out for a spin, and then it started to leak. I noticed the more in town driving i did, the more it leaked so i thought it might be the oil pan. Put a new oil pan gasket in and still leaked. after 9 years and 3 trys this has got to be it. As far as the gap goes, the Pontiac engineers must have known this happens otherwise why would they have put it in the shop manual to put a bead of sealer between the main seal and oil pan gasket under the cap? Man, i wish I'd seen that before!!!

[Cardo]

Just a quick update..... 400 miles, still no leaky! I believe 61-63 was right on this one. First time this car has not leaked oil in the 9 years i've had it! To others with persistant rear main leaks, take note!

[quicksilver97ta]

Originally Posted by Cardo

Just a quick update..... 400 miles, still no leaky! I believe 61-63 was right on this one. First time this car has not leaked oil in the 9 years i've had it! To others with persistant rear main leaks, take note!

Congrats, that got to be a feeling of relief.

[hurryinhoosier62]

Cardo,
Question; do people still race across the Sherman Minton Bridge like we used
to back in the late 70's and early 80's? Lord, I miss being home!!!

[Cardo]

Yea, sometimes late Friday and Saturday nights, from what i hear. I live just off of 265 @ Charlestown road and you often hear the crotch rockets running across there at night. Sounds pretty wicked, but i just don't have the Kahunas for that... or just too much sense!

[Cardo]

Yes Q Silver it is nice not to constantly be cleaning the trans and exhaust off! I finally feel comfortable with driving this car some distance if i want. I just hope that others look for this, It was extremely frustrating.

[hurryinhoosier62]

Cardo,
Sorry, you just brought back some old memories. Cruising Frisches's on Spring Street, hanging out at Ohio Valley and Harrison County Dragways. I miss the
the Greater Louisville area. Hopefullly, we will get our house here in Wisconsin
sold quickly.My wife just started a new job in Louisville.