carb vacuum leak

[bosco]

After tightening my carb (Weber) attachment nuts I noticed my idle would not return to 850 anymore...it would idle higher. I sprayed carb cleaner on the gasket and I definately have a leak on the back (firewall) side. I'm not sure if I've warped the base of the carb or not. I have adjusted the nuts to the point where the idle now comes back down (although it takes longer). When I spray carb cleaner right by the carb linkage it still decreases the idle but does not seem to anywhere else (it also seems there is a cutout in the heat shield there so maybe my heat shield gasket is leaking). My question is.....if i take the carb off can I file down the base somewhat if its warped on one side? Also, when I originally put the carb on I did not use any gasket sealer...either on the heat shield gasket or the thick carb gasket/spacer(with plastic eyelets). When I redo it should I use some......might that help?

[opelgtmaster3]

dude you always want to use gasket sealling. it helps alot. next time you sould use it to prevent leaks

[Scott McDonald]

I used a (dealership-shop) gasket sealer made for gasoline/heat applications. They called it, "Pookie." They have different "Pookie" for different apps.

So I would suggest going to an auto dealership and asking the maintenance department if they have a sealer that fits your need, and if you can buy/use some.

BTW, the stuff is nasty. Varsol and a brush got it off my hands. And, it dries fast.

[tekenaar]

After tightening my carb (Weber) attachment nuts I noticed my idle would not return to 850 anymore...it would idle higher. I sprayed carb cleaner on the gasket and I definately have a leak on the back (firewall) side. I'm not sure if I've warped the base of the carb or not. I have adjusted the nuts to the point where the idle now comes back down (although it takes longer). When I spray carb cleaner right by the carb linkage it still decreases the idle but does not seem to anywhere else (it also seems there is a cutout in the heat shield there so maybe my heat shield gasket is leaking). My question is.....if i take the carb off can I file down the base somewhat if its warped on one side? Also, when I originally put the carb on I did not use any gasket sealer...either on the heat shield gasket or the thick carb gasket/spacer(with plastic eyelets). When I redo it should I use some......might that help?

NEVER use sealant of any kind in carburetor or it's mounting flange!

No matter how thinly and evenly applied, it will almost always cause "bleed-over" problems in those tiny vacuum and/or gasoline passages.

[jerseyopel]

Are you sure when you installed it you torqued it properly?? Remember to go corner to corner and never use sealant.

[Dmcbrass]

I don't understand why using gasket sealer on the carbureter base could cause contamination in the carbureter. ( plugging vacuum or gasoline passages). The carbureter base is on the outlet of the carbureter not the inlet. Any sealer that leaked would be sucked into the engine not into the carb. This would be no different than any other gasketed surface. Intake manifold etc...
I definately recommend using a gasket sealer as does OGTS. Permatex hi-tack is a good choice.

[bosco]

I just used "Hi Tack" on mine. I figured that since the heat shield and its gasket, as well as the carb gasket were downstream of the jets I should be ok. It "seems" to have worked. The only thing I can see is that when I remove the carb next time there will be more of mess to clean up.....

[tekenaar]

I don't understand why using gasket sealer on the carbureter base could cause contamination in the carbureter. ( plugging vacuum or gasoline passages). The carbureter base is on the outlet of the carbureter not the inlet. Any sealer that leaked would be sucked into the engine not into the carb. This would be no different than any other gasketed surface. Intake manifold etc...
I definately recommend using a gasket sealer as does OGTS. Permatex hi-tack is a good choice.

And you would both be wrong . . . and here's definite proof :



. . . either gasket sealer or even a thick, sufficiently compressible gasket could potentially block the tiny, arrowed idle mixture or vacuum ports of the 32/36's primary and secondary barrels! Would you really want to chance it with <0.5mm openings?!

[GTJIM]

There has been more damage done to engines with injudicious use of "gasket goo" than any other single cause. The introduction of RTV sealants is both a blessing and a curse - wait till YOU find out what happens when solidified RTV gets into an oil gallery! If new gaskets don't seal a carb base then there is usually a warping issue that needs to be addressed anyway. Tighter nuts don't necessarily mean more or better sealing.

[Dmcbrass]

The ports on the Carb flange are indeed vacuum ports; however, they work backwards to what we normally think of a vacuum port. The intake manifold is operating at a lower pressure than the carb which causes the ports to create vacuum in the carbureter. This pulling of a vacuum by the engine on the carb will pull any material which finds its way into the port opening, into the intake manifold.

[GTJIM]

Unfortunately there is only 10 to 12 psi, maximum, of differential air pressure available during engine operation. 100 psi from a compressor will not shift cured RTV from small passages. Any bits that do "find their way .. into the intake manifold".. travel further and inevitably get trapped between valve faces and seats or jammed down beside the top piston land into the ring grooves.
Anything that does not get "sucked" out prevents proper operation of the carburettor - it is better to not be there in the first place!

[baz]

got to go with otto and jim
better to use some wet and dry paper on a good level surface and address the warping on the carb than put gunk on ,that as every one admits will be pulled into the engine where only air and petrol should go

[GTJIM]

It's even better being agreed with!

[tekenaar]

It's even better being agreed with!

Especially if agreed with by the "Terminator"!

[BDD]

If the plastic stand-off spacers could be removed from the thick base gasket, would it then seal better without adding sealant?

[hrcollinsjr]

If the plastic stand-off spacers could be removed from the thick base gasket, would it then seal better without adding sealant?

IMHO the plastic stand-off spacers help guard against overtightening the carb base and ruining it.

Harold

[BDD]

So that thick gasket should work without sealant?

[yellaopelgt]

try permatex copper spray on the gasket....it wont break off in pieces and it seals things up a bit. Thats what I did ,and the gasket will even come off the base later on without making a big mess.
HTH
Joe

[hrcollinsjr]

try permatex copper spray on the gasket....it wont break off in pieces and it seals things up a bit. Thats what I did ,and the gasket will even come off the base later on without making a big mess.
HTH
Joe

I very seldom use sealant on carb base gaskets, only when Murphy has come for a long stay.

Harold

[BDD]

Does anyone know what sealants are recommended with this gasket?
OGTS does not recommend RTV but they do recommend some sealant.

Since this as a thick, relatively compressible gasket, without the stand-off spacers it could compress a bit and therefore seal without putting enough force on the carb base or intake manifold to warp it. The gasket flexes more readily than the metal. A thin gasket could never do this and must have perfectly flat surfaces to go against. The flexible gasket would also compress and tend to conform to the surfaces it is against.

OGTS does say in their literature though (if I'm remembering right) that the plastic spacers help prevent warping.