Carb Stud Thread Sealant

[mwebfj60]

What have you used to seal the carb stud threads in a 2F manifold? My plan was red Loctite but thought something softer may be better? This is the last time I want to mess with this setup until the upgrade to 3fe head a couple years from now.

 

[GeologistFelix]

I can't speak from experience -- my intake manifold was in good enough shape to clean that gasket surface without taking the studs out.

That said, I think the amount of potential vacuum leakage that can get through the threads and the gasket/isolator on that corner will be negligible. Like, 'impossible to detect with anything but aerospace-grade instruments' negligible. As well, any material other than air that manages to get sucked in through that convoluted path will have to be so small that it will literally make no difference to the engine.

That said, you could coat the threads with fuel-resistant RTV/instant gasket (Amazon.com: Permatex 85420 Permashield Fuel Resistant Gasket Dressing & Sealant, 2 oz Tube: Automotive or similar) when you install them, it would be hard to go wrong with that. That specific example is rated to 500°F, which is hotter than your intake should ever get (I'm pretty sure your carb would be about ready to spontaneously combust, at that point).

 

[Output Shaft]

No sealant is necessary. The 2F emissions system already has a few small built in vacuum leaks that are part of the design. No air is going to leak past those threads. And if a microscopic amount does, it won't make any difference to anything.

 

[mwebfj60]

Good deal, I will use the Permatex just as a precaution as I have some in shop. I understand negligible air leak but I went as far as putting one of the Denso vacuum actuators hooked to a switch in the dash to control the "designed" vacuum leak on the HAC system.

 

[Output Shaft]

Yes, but take in mind that the little vacuum leaks that are part of the original emissions equipment (HAC) were accounted for by Toyota when it jetted the carb. They are are not detrimental or evil vacuum leaks, but contribute to the correct air fuel mixture.

 

[mwebfj60]

Yes, but take in mind that the little vacuum leaks that are part of the original emissions equipment (HAC) were accounted for by Toyota when it jetted the carb. They are are not detrimental or evil vacuum leaks, but contribute to the correct air fuel mixture.

When I was Desmogging and studying the FSM, I put more thought into this than was probably necessary. I played around with the HAC circuit for a while, leaving it as is with the vacuum leak below altitude, with a blue VCV, with the green as limiters to the leak, with the port on the carb capped, and finally decided capped was the best route for daily driving at my altitude (230). I wanted to keep the HAC for altitude trips and didn't want to pop the hood while heading up the hill so I just installed a switch in the dash to open the vacuum to the HAC when needed.

 

[Spike Strip]

Anti-seize is prolly better on those threads than RTV.

 

[CaptClose]

Well damn...I replaced the studs without using anything. But I think it will take way more than 20" of vacuum to pull air past those threaded carb studs anyway.

 

[mwebfj60]

Anti seize seems like a great way to go, piece of mind both ways.

 

[Spike Strip]

Do yourself a favor if you go with Anti seize: Use good anti-seize. Not the cheap copper crap they usually have in the Auto parts stores.

Amazon.com: Never-Seez NMCBT-8 Black Gray Mariners Choice Anti-Seize, 8 oz. Brush Top Can: Industrial & Scientific