Carb Bolt Holes

[XCScott]

I was wondering what tap size should be used to re thread stripped bolt holes that hold the carb onto the manifold.

[Bear45-70]

If you are trying to retain the original thread size, you can't just tap the hole. You need to use helicoils in the holes. The other option is to up size the hole by tapping them to SAE 1/4 X 20 and use the right length 1/4 X 20 bolts. To prevent this kind of stuff in the future, get a friclin' torque wrench. Steel bolts and screws will always win over aluminum and pot metal threaded holes.

[coolbeans]

Another option is to use a much longer bolt that will reach out the far side and put a nut with a lockwasher on the other side.

[Bear45-70]

Another option is to use a much longer bolt that will reach out the far side and put a nut with a lockwasher on the other side.

Be careful with this one. Too long a bolt will punch a hole in the carb body, making it junk.

[coolbeans]

I agree....to be more specific: another option is to use a bolt that will just clear the threaded carb holes and put a nut with a lockwasher on it.
It's still probably better to tap it out to 1/4" but I know what it's like to not have a tap and die set...

[Wheelman-111]

Greetings:

If there's a Harbor Freight Tools store in the Bad Part of your town, they sell a very cheap tap set that's Just good enough to do the deed. I recommend tapping to 1/4" x 20 for the ease of performing the operation and of locating said quarter-inch bolts in the needed lengths. It will not be necessary to pre-drill the stripped threads in the carb - just run the tap through, creating cool new 1/4" threads in the flange.

You may have to trim the tips of the 1-1/2 (near-side) and 2" (far-side) bolts to avoid what The Bear describes. You must also drill the manifold and carb insulator out to 17/64ths or so to permit insertion. Go easy on the Wheaties when you snug this up. The quarter-inch threads are only a little stronger.