Carb intake gaskets

[10musketeer]

I have a Weber carb and have the standard air leak that I'm trying to seal up at the head on the intake manifold. What should I use? Will standard paper gaskets stand up to the heat? How much heat are we dealing with right there next to the exhaust manifold? I've looked at the RTV sealants including the copper hi-temp and the black oil-resistant, but both say they're not recommended for head gaskets and areas in contact with gasoline, which this area will be.

Any thoughts?

 

[racingenglishcars]

I think paper (cardboard) will stand up to the heat, on the intake part, but not for the exhaust part. And since the gasket is normally one piece, I would just go with the standard part. A little sealant can't hurt, but it should be fuel resistant. (actually nothing wrong with using exhaust sealant, also on the intake part) There are many silicone / permatex. etc sealants available that will do the job. Just a little on both sides of the gasket.

 

[John Moore]

I usually fit that gasket dry and make sure it's torqued properly. 15#'s I think. Remember that if the gasket comes with a silver side it goes towards the hot side, which in this case is the manifold.

 

[Morris]

Check to make sure the mounting flange on your intake manifold is not fouling the exhaust manifold flange. You may need to file a bit off.

 

[racingenglishcars]

That's the whole point, like Morris says. When installing an aftermarket manifold for the Weber, it probably will not fit. The flanges will be too thick, too thin or too wide. If it appears to fit, but leaks, then a thicker gasket might do, or some sealer, or sime filing. On rare occasions the carb and manifold are too heavy (sidedraft webers) and the gasket is pulled away at the top. The Alfa uses a brace to hold the carbs up.

 

[tosoutherncars]

John, I just want to make sure we're all talking about the same thing. You're referring to the long gasket, with the rectangular holes for the exhaust manifold as well as the intake manifold?

If so, yes, it's a metal-wrapped gasket, normally fitted dry. And if you've got a leak, the common wisdom seems to be that the intake and exhaust manifolds foul each other, causing the intake not to sit flush on the lower edge (where it's not really visible).

If you have some machinist's dye, you might consider putting some on your exhaust mani / headers, test-installing your intake mani, and seeing where they interfere (assuming that it's not obvious).

-Duncan

 

[10musketeer]

Well I knew I had a problem when I took the intake header off. There was no gasket at all and I could see that the exhaust manifold was in fact interfering. The weber manifold at the head is too thick (or at least thicker than the exhaust manifold) and they are not mating well. The PO used a combination of large washers with washers cut in half to achieve a less than adequate fit.

Is there a source for the exhaust manifold gasket w/ weber conversion? I have to admit I haven't looked hard.

 

[tosoutherncars]

Aha! Definitely sounds like the source of your problems... The gasket itself is the stock one - there is no real difference at that joint between the stock setup and the Weber and/or headers. (That is to say, the intake & exhaust passages & bolt holes haven't moved!)

To confirm: once you have the exhaust mani in place, the intake mani cannot be fitted up flush with the head, correct? Where is it interfering? Right at the head? or further back, the bodies of the two manifolds?

Or is it just the the "ears" that are used to hold both manifolds can't be tightened down adequately due to different flange thicknesses? If that's the case, it's definitely going to be a case of getting out the die grinder...

-D

 

[tosoutherncars]

Thank you, Moss Motors. Is that what you're looking at? If you couldn't see a gasket at all when you removed the prev. intake manifold, something is definitely missing...

-D

 

[10musketeer]

At this point is just seems to be at the ears. Hopefully tomorrow I'll get a better look at it. I'll get the standard gasket on order asap.

 

[jlaird]

I think that is funny in a sick kind of way. Oh well no gasket, I'll just do without. Gesh DPO stuff.

 

[bugimike]

I had a similar problem when fitting an after-market header with the stock intake manifold! The ears for intake and exhaust manifolds were of different thicknesses, the aftermarket exhaust being thicker. As mentioned above, a little judicious grinding to even them up was all that was required!! The stock gasket (as someone else mentioned above!) should work just fine with the Weber too! /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif

 

[Billm]

Is this for an A-block or a 1500?

 

[10musketeer]

A block -1275

 

[10musketeer]

UPDATE:

I thought I would let you know how this turned out.

Instead of grinding the manifold, I decided to use a semi-permanent fix to make sure a manifold leak was my problem. I used large washers with washers cut in half and held together with epoxy to make up the difference in the ears. I cleaned the manifold and put it back together with a gasket and to make sure it sealed this time I used gasket sealer (RTV #2) that has a 400*F temp limit (thanks to Bugeye58 for the temps (+/- 200*F)). After two days of driving it, the leak is gone and the carb works very well. It starts up right away and has no run on at shutdown. The power is constant throughout the RPM band now and the timing is much more predictable.

Now that I know a leak is definitely my issue, I'll run it for the summer, then this winter I'll take it apart and grind it so that they mate well.

Thanks for all the help guys. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

 

[jlaird]

Boy, isn't it nice when a plan comes together. Good on ya.

 

[DrEntropy]

"Have pyrometer. Will travel."

 

[Bugeye58]

"Have pyrometer. Will travel."

Yup. I travelled out to the garage, and then ran the '72 for ten miles to get it to operating temp! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

Glad things are working out for you.
Jeff