I overtightened a couple of the bolts that hold the fuel bowls on my 670 SA. They stripped out. I want to heli-coil the bolt holes but the bolts have sort of a wierd thread size.

At first I thought they bolts had 1/4 20 threads but it turns out it it's something like 24 - 12 . Anyway it's very close to 1/4 20.

If I use a 1/4 20 heli coil kit should I try to reuse the original bolts even though the thread is slightly differant or should I try to find 1/4 20 bolts of the same length?

Also, Has anyone ever use a heli coil kit? Any tips or things to keep in mind?

Thanks.

 

You should use the right size Heli-Coil, which is NOT ¼"-20.

Your original guess was correct, the size is #12-24. You can get the kit from NAPA or a real bolt & screw place.

I happen to have one, for exactly that purpose.

About the only tips I can think of, is don't screw up while you're doing it; once you hose a hole that way, the casting is pretty much trash. And be careful if it's a throttle-plate to main-body screw, some of those are very close to the outer edge of the casting, and the casting is prone to crack around the screw hole.

 

If you can't find the parts locally;

Holley
Part #26-3 - Heli-Coil Inserts
Part #26-2 -Installation Tool Kit

Obviously your not the first to do this, it they have part numbers for this situation.

The instalation tool kit is on the very pricey side @ 68 bucks, and the heli inserts are 17 bucks. You can get them from Summit.

Ron

 

I got the #12-24 kit. It was expensive at $45. It was worth it. Three of the eight fuel bowl bolt holes were stripped. The helicoils were a good fix. Now I'll just snug them up to keep from stripping them again.

 

The absolute best & consistant way is using an inch pound torque wrench.
I like about 20-22in# w/Vasoline on the float bowl screws...

Ron