carb vacuum leak
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Thread: carb vacuum leak

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    Member My location bosco bosco's Avatar
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    carb vacuum leak

    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?
    Next stop the Twilight Zone.....

    1973 Opel GT

    Previously:
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    1973 Opel Manta
    1977 Datsun 280Z
    1993 Nissan 300ZX

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    Member opelgtmaster3 is on a distinguished road
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    carb

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

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    Air Muir s Air Tir! Scott McDonald Scott McDonald's Avatar
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    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.
    Is fhearr deagh chainnt na h-asail na droch fhacal faidh.-The good speech of an ass is better than the bad word of a prophet.

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    Cunning Linguist Site Supporter My location tekenaar will become famous soon enough tekenaar's Avatar
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    Angry Sealer for carbs? . . . NOOOOO!

    Quote Originally Posted by 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?
    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.


    1960: '61 Rekord PII 1.7 3S 3.9 '69 Kadett LS 'sprint' 1.9 3A 3.18
    1970: '70 GT 1.9 4S 3.44 '72 GT 2.2SSD 5S 3.44 '72 GT 2.4FI 5S 3.44P
    1970: '73 GT 1.9FI 4S 3.44 '75 1900 1.9FI 4S 3.44
    1980: '85 Bitter SC 3.9FI 5S 3.44P
    2000: '09 Solstice GXP Coupe 2.0 SIDI VVT "Stage 2" Turbo 5S 3.73P


    "De inimico non tantum loquaris male, sed cogites."

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    Member jerseyopel is on a distinguished road
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    carb to manifold

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

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    Member My location Dmcbrass Dmcbrass's Avatar
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    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.

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    Member My location bosco bosco's Avatar
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    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.....
    Next stop the Twilight Zone.....

    1973 Opel GT

    Previously:
    1971 Opel GT
    1973 Opel Manta
    1977 Datsun 280Z
    1993 Nissan 300ZX

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    Cunning Linguist Site Supporter My location tekenaar will become famous soon enough tekenaar's Avatar
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    Arrow 32/36 base visit . . .

    Quote Originally Posted by 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.
    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?!
    Last edited by tekenaar; 06-01-2012 at 04:37 PM. Reason: proof pic was gone?!!


    1960: '61 Rekord PII 1.7 3S 3.9 '69 Kadett LS 'sprint' 1.9 3A 3.18
    1970: '70 GT 1.9 4S 3.44 '72 GT 2.2SSD 5S 3.44 '72 GT 2.4FI 5S 3.44P
    1970: '73 GT 1.9FI 4S 3.44 '75 1900 1.9FI 4S 3.44
    1980: '85 Bitter SC 3.9FI 5S 3.44P
    2000: '09 Solstice GXP Coupe 2.0 SIDI VVT "Stage 2" Turbo 5S 3.73P


    "De inimico non tantum loquaris male, sed cogites."

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    Old Opeler My location GTJIM will become famous soon enough GTJIM's Avatar
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    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.
    GTJim
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    J D Henry
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    Member My location Dmcbrass Dmcbrass's Avatar
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    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.

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    Old Opeler My location GTJIM will become famous soon enough GTJIM's Avatar
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    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!
    GTJim
    Opel Owner since last Century!

    Copyright 2000-2009
    J D Henry
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    baz
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    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
    Copyright 2003-2012 barry williams
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    Old Opeler My location GTJIM will become famous soon enough GTJIM's Avatar
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    Up Side!

    It's even better being agreed with!
    GTJim
    Opel Owner since last Century!

    Copyright 2000-2009
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    Cunning Linguist Site Supporter My location tekenaar will become famous soon enough tekenaar's Avatar
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    Wink

    Quote Originally Posted by GTJIM
    It's even better being agreed with!
    Especially if agreed with by the "Terminator"!


    1960: '61 Rekord PII 1.7 3S 3.9 '69 Kadett LS 'sprint' 1.9 3A 3.18
    1970: '70 GT 1.9 4S 3.44 '72 GT 2.2SSD 5S 3.44 '72 GT 2.4FI 5S 3.44P
    1970: '73 GT 1.9FI 4S 3.44 '75 1900 1.9FI 4S 3.44
    1980: '85 Bitter SC 3.9FI 5S 3.44P
    2000: '09 Solstice GXP Coupe 2.0 SIDI VVT "Stage 2" Turbo 5S 3.73P


    "De inimico non tantum loquaris male, sed cogites."

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

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    Tennessean Site Supporter My location hrcollinsjr will become famous soon enough hrcollinsjr will become famous soon enough hrcollinsjr's Avatar
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    Quote Originally Posted by BDD View Post
    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

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    BDD
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    So that thick gasket should work without sealant?

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    No....its not a Buick.... My location yellaopelgt is on a distinguished road yellaopelgt's Avatar
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    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
    What ...we got here...is........failure......................... to communicate....
    Some men,you just cant reach...so you get what we had here last week...which is the way he wants it.
    Well, he gets it...I dont like it, any more than you men...


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    Tennessean Site Supporter My location hrcollinsjr will become famous soon enough hrcollinsjr will become famous soon enough hrcollinsjr's Avatar
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    Quote Originally Posted by yellaopelgt View Post
    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

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    BDD
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    Smile

    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.

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