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Rtv On Carb Gaskets? Yes Or No?


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I recently looked into this and most people recommended NOT to use RTV sealant on intake gaskets as if some comes loose on the inside it can make its way back into the carburetor (due to reversion pulses) and cause problems. I put my DCOE's on dry, using solid spacers (bakelite type) with gaskets on each side. If I have an air leak I will check the surfaces for flatness and have them surfaced if they are way out. Otherwise I would not have a problem with a thin skim coat of RTV on the gaskets. I think issues occur when folks are heavy with RTV application and it spooges out all over. One would also want to make sure that whatever sealant used is impervious to gasoline.


--Fred '74tii & '69 DCOE

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The only liquid gasket maker that is okay on an intake system is anaerobic sealer. Standard RTV hardens in the presents of air. Anaerobic sealer hardens when there is a lack of air. When using standard rtv, the bits on that squeeze out of the mating surface will harden and these can fall off into the intake manifold and cause issues. Anaerobic sealer hardens in the inside (the sealing surface). Any part of the anaerobic sealer that is exposed to air will remain gel like. I have used Anaerobic sealer on superchargers with no problems. If you do have a paper gasket, I would recommend just going with that as it sounds like you have been told already.

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NO, NO NO.  Don't use silicone for gasoline related applications.  This has been posted on the FAQ (and many other blogs) many times.  Gasoline is essentially a solvent for RTV and the sealant will eventually turn mushy (with the possibility of migrating into the inner orifices of the carb).

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NO, NO NO.  Don't use silicone for gasoline related applications.  This has been posted on the FAQ (and many other blogs) many times.


Well I never paid any attention because I have been a tii guy for years :) A quick search of the FAQ turned up a few posts not hundreds.


However, I did some research and learned something new--and relevant to the issue at hand. According to the Permatex website: "Silicones are not recommended for use in a gasoline environment. The gasoline will attack the product."


Several companies claim to make gasoline-resistant sealers. Not sure if they are all anaerobic or not. Here are three that I was able to find and review the MSDS to verify claims. Have not used any for carbs (though I do like Hylomar for some sealing applications), so this is not a recommendation of any:


Permatex #29132 MotoSeal 1 Ultimate Gasket Maker Grey: "resists high temperatures and performs well in a gasoline environment."


Hylomar: "resistant to a wide range of fluids including most industrial fuels, gasoline"


SS300 Gasoline/Solvent Resistant RTV Silicone: "Exceptional gasoline, oil & solvent resistance compared to normal RTV silicones."

--Other than a seven-day immersion test it does not say how long it will last.



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