'64 Intake Seepage

[Mark H.]

I've just turned 500 miles on the rebuild of my '64 327/300. I have noteced on each side of the intake, in the middle section across from the carb, that there is a slight amount of wetness beween the intake and the block. No puddles or drips, but if I run the edge of a paper towel in the seem, it comes up wet. This is not the case on the front or rear 1/3 of the same seam. It does not appear to be anywhere one would use a sealant - I ultra-coppered the ends in lieu of the rubber pieces and there are no leaks there. If I pull the intake to try to address the problem, my question is what to do about the thread sealer on the bolts. Cleaning the bolts is easy - but I am reluctant to run a tap in the holes for fear of knocking crud into the top of the engine. How do real mechanics deal with that? Just use more thread sealer and forget it? try to catch the crud with a paper towel from underneath?

I hate doing things twice, but if I do it a second time don't want to end up worse off than I am now. Any suggestions appreciated. Thanks.

[Joe L.]

Re: '64 Intake Seepage

Mark------

I can't tell you how "real mechanics do it", but I can tell you how I do it. I lay down a generous layer of paper towels in the intake valley after the manifold is off, being careful to ensure that the area on the walls of the valley right up to the cylinder head are completely covered. Then, you can run a tap or thread chaser in the intake bolt holes in the cylinder heads with all of the debris falling onto the paper.

The problem that you are describing is very common on Chevrolet V-8s. One thing that causes it to be worse in the center area that you described is the heat crossover passage. Heat from this passage radiates out and degrades the thread sealer used on the bolts that go through to the intake valley.
Several things are critical to getting a good seal:

1) The intake bolts and their threaded holes in the cylinder heads must be ABSOLUTELY CLEAN of any oil or debris;

2) You must use a high temperature sealant. Permatex makes a high temperature bolt thread sealant that is marginally effective in withstanding the heat radiated from the cross-over passage. However, the heat involved may be more than any sealer that I know of can withstand over time.

[Dick W.]

Re: '64 Intake Seepage

Joe, I have had good success with Loctite PST on the threads. I have not had any leakage problems over the years.

[Mark H.]

Re: '64 Intake Seepage

Joe -

Thanks. The leak, though, is not around the bolts. I did seal these on assembly and they appear fine. The leak is in the seam between the intake and the block. Is that also common?

[Joe L.]

Re: '64 Intake Seepage

Mark------

The only place that the intake contacts the block is at the ends. You said that you had used Ultra Copper to seal that junction and had no leaks there. So, where's the leak?

[Mark H.]

Re: '64 Intake Seepage

Along the gasket line from front to back, in the seam between the block and intake, even with the carb (the "middle third" of the intake). I can't really tell if the seepage is on the block side or the intake side of the gasket.

[Joe L.]

Re: '64 Intake Seepage

Mark-----

There is no gasket line from front to rear with respect to the intake and BLOCK. The area that you are talking about is between intake and CYLINDER HEAD. In this area any oil seepage is due to

1) a valve cover gasket leak which is VERY common;

2) oil seepage past the intake manifold bolt threads which is VERY common;

3) oil "wicking up" through the intake manifold gasket which is VERY UNCOMMON

4) an oil leak caused by an improper fit of the intake manifold with the cylinder heads due to an angular mis-match. Usually, this sort of a leak will be accompanied by a vacuum leak, but the vacuum leak may be partially "sealed" by the seeping oil. This is rather uncommon, too.

[Patrick H.]

Re: '64 Intake Seepage

I'd go for #3 or #4 on Joe's list, but I think the oil is sqeaking past the gasket, not wicking up it. My car does this, and when I look at other cars I often see the same thing. It is NOT from the bolts, which I realize commonly leak. As Mark noted, it appears in the little valley between the heads and the intake. I can drive about 50 miles in a day, open the hood, and the intake bolts are completely dry. Only the little valley has some oil seepage. I run a paper towel along the bottom of the valve cover, and no oil noted.

I had a lot more leakage before I swapped out my intake gasktes 2 years ago. I decreased the seepage significantly by using Fel-Pro Printoseal gaskets. Despite what is often read, next time I will put a thin line of sealant along both sides of the intake gasket, running from the #3 to #5 intake runners, and from the #4 to #6 intake runners. The ONLY place I now get the exact seepage Mark describes is actually between the heat crossover and the #5 or #6 intake port. I somewhat surmise that the small amount of Gaskacinch I applied between the exhaust crossover and the #4 or #3 intake runner actually keeps that area from leaking.

So you're not alone, Mark. Use a VERY thin line of sealant around every passage on both sides of the intake gasket. Use the Fel-Pro, which is slightly thicker than average and has those nice seals on the ports. And, hopefully that will help. I'd love to know if it does or does not. Mine does not seep enough for me to yet remove the intake and try again.

Patrick

[Mark H.]

Re: '64 Intake Seepage

Joe -

Of course, you are right - the seepage is between the intake and the heads. It's been a long week.

[Mark H.]

Re: '64 Intake Seepage

Thanks, Pat. I used Fel-Pro when assembling the engine, but only used the ultra-copper at the ends in place of the rubber (?) pieces, and the ends are dry as a bone. I don't have a bad enough problem (yet) but 250 miles ago the seam that is now leaking wasn't, so I fear it will get worse. If I tear it down and replace the gaskets I'll use the sealant as you describe and see if that helps.
Mark

[Charles M.]

Re: '64 Intake Seepage

Mark - Can you post a picture of the leak in question?

[Joe L.]

Re: '64 Intake Seepage

Patrick------

A good part of the reason for oil getting past the intake gasket in the center area is the effect of the very high exhaust heat at the cross-over passage. To one degree or another this heat will degrade just about any gasket over time. However, if there is a slight angularity problem in the mating of the heads and intake manifold, the degradation will take place MUCH, MUCH more rapidly.

[Patrick H.]

Re: '64 Intake Seepage

Joe,

I don't doubt that angularity will make it worse. The interesting thing is that my oil appears just ahead of the #5 intake port.

Overall it's a lot better than it was. Before I re-gasketed, I had so much oil getting sucked into the exhaust crossover and burned that I went through a quart every 500 miles. The kicker was - no leaks on the outside! Terrible vacuum leak, though.

The car runs MUCH better now. So much so that I can tolerate a small leak that I have to wipe up about twice a season of driving.

Patrick

[Dick W.]

Re: '64 Intake Seepage

I guess it would help if'n I would read the whole post. I wuz a thinkin' about water seepage around bolts. Ultra Copper works very good on the gaskets as long as you do not subscribe to the theory that if a little is good, a whole lot must be better. Just use a very thin bead and it works wonders.

[Mark H.]

Re: '64 Intake Seepage

Sorry, I haven't graduated to the 21st century. Still use cameras that take film (christmas is coming, though), and I doubt a picture would tell much - there isn't much oil to see and it's right along the head-gasket-intake seam even with the carb.