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I don't ever use RTV on gasket surfaces on B20s, but I am dealing with a stubborn intake / exhaust gasket on my daily driver. I'm on the second gasket, and cannot get the intake to seal. Both surfaces are clean and the intake was trued up by a reputable machine shop. Have the correct washers, the intake / exhaust surfaces where the washers go are even. Nuts were all torqued evenly to 18 ft-lbs. Even tried up to 25 ft-lbs. I suspect the gasket material is a different composition than that used many years ago and just does not squish like days of old.
At any rate, since I cannot get the gasket to seal I'm going to (begrudgingly) use RTV. I was going to use Permatex Black, but the Permatex Copper says it's more flexible - little confusing. I think the Copper may be the way to go.
I know this has been covered many times, but since I never used RTV in the past, I usually didn't pay attention to others suggestions...shame on me! So now it's my turn. Any thoughts on the Black vs. Copper? (I think the Blue will not stand up to the temperatures of the exhaust manifold.)
Thanks.
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'60 PV544, '68 220, '70 145, '86 745T
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Background: Just haven't been able to fix an intake leak at the gasket between the intake / exhaust manifold and head. Could never get the idle to stay below about 1000 rpm.
Did all the right things like;
1. Checked the intake for cracks and leaks;
2. Checked the carb. bases for cracks or leaking gaskets;
3. Had the manifold "trued up" at a trusted machine shop;
4. Made sure both surfaces were spotless before installing a new gasket;
5. Torqued all the nuts evenly to about 17 ft-lbs.
I went through this 4 times. Each time it always seemed proper when it was done. Within 200 miles though, I'd notice the idle speed creeping up again and just not a good idle (some miss).
Well, I took it apart for the 5th time. I didn't want to, but was resigned to using some kind of RTV to seal this sucker up. So I pulled it apart again and could find no apparent reasons for the leaks.
Except - here's the dope slap moment. The manifold was machined about 0.040" when it was surfaced at the machine shop. I never even thought of compensating for that 0.040". So what was happening was the locating rings that insert between the head and intake manifold were keeping the intake from sealing all the way. It wasn't missing by much, I'll bet less than a thousanth or two, but it was just enough to prevent me from getting the idle down to normal.
This was really a dumb mistake. No harm done other than to my pride!
Now it's working like it should. It's nice to have this monkey off my back that I've been dealing with for better than a year.
--
'60 PV544, '68 220, '70 145, '86 745T
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That would have been a toughie to find - great work!
Rhys
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If you are blowing gaskets you have serious problems. Did you notice loss of power before blowing the gasket? You may have a collapsed muffler.
Never use silicone on an engine.
The gaskets should work fine dry, but I drown them with silver frost which makes them infinitely reusable.
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Three 164's, Two 144's, One 142 & a partridge in a pear tree.
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The leaks are on the intake side, not exhaust so I doubt there is a collapsed muffler.
I agree that they "should" work fine dry, but for some reason I just can't get them to seal. The gasket will be good for a few hundred miles and will then begin to leak. So I wouldn't describe it as "blowing out".
What is silver frost? Is that like anti-sieze?
--
'60 PV544, '68 220, '70 145, '86 745T
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What do you have for intake & exhaust manifolds?
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Three 164's, Two 144's, One 142 & a partridge in a pear tree.
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Cast iron combination manifold, the version with the secondary butterflies (which have been removed and the holes blanked off).
--
'60 PV544, '68 220, '70 145, '86 745T
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black is an adhesive and a sealer, blue is a sealer, and orange is a high temp sealer. i used gallons of rtv when in the trade but now that every thing does not have to be completed in 2 mins. or less i only use permatex #2 or a rubber cement product(gasket cinch).the surfaces must mate properly.
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Copper is the product designed for high temp use. I've built headers in the past and installed them without gaskets, just a thing smear of copper RTV. Works well. I use black in other situations, rarely, and never use blue because I don't want to look at it. Usually blue indicates someone unskilled.....as the stuff is used far too frequently.
But for the exhaust, copper is the best bet. Remember though that the only solvent for silicone is gasoline.
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Rhys, I'll bet you, Phil S., and Art have seen more blue RTV smeared over just about anything as anyone out there. I had to chuckle when I read your post. As is typical of your responses, spot on. To the OP, don't slobber it on too thickly, I'll bet you are looking for a small gap to fill.
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Actually I've been pretty fortunate with my cars, having obtained them from owners who generally have had them serviced at the dealer's shop for longer than most do. I speak cautiously, because I am not very far into the one 244ti acquired from an "enthusiast", who loved the IPD catalog, it seems. I have removed enough pretty colored zip ties to fill a coffee mug, but no blue boogers yet.
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Art Benstein near Baltimore
My father said there are two kinds of people in the world: givers and takers.
The takers may eat better, but the givers sleep better.
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