Float bowl threads stripped. Helicoil?
 

Noticed today I had a slight fuel leak. Turns out the threads on my demon carbs where the front fuel bowl mouns to the body are stripped out. It looks as if they were helicoil inserts anyhow.

My question is, how do those helicoils work? Would I have to drill out the old threads, then press in the helicoil? I think the bolts are 1/4" bolts.

MT,
I doubt that they were helicoiled, what you are seeing is just the threads pulled out of the carb body. I have fixed more of these than I can remember. They are an unusual thread size, 1/4 x 24 I think ? I have the Holley helicoil kit at the shop for them. Pretty easy repair IF you have done helicoils before. If you dont feel real confident then this is not the place to learn. If you are going to try it yourself, get the HeliCoil kit and practice on a piece of scrap aluminum. The trick to getting the "tang" out is to use a small square nosed punch and "smack" it real hard and quick with a small hammer. If you try any other way it will just twist and make a mess.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Helicoil is a wound-wire device. They tend not to be as reliable nor suitable for repeated use as a thread insert. An insert is basically a piece of threaded rod with a threaded hole inside it. The insert is retained either via a chemical locking compoind, mechanical staking via built-in retainers or external staking, or both. They're usually the next thread size up from your stripped hole. In something like a carb body where you have a shallow, blind hole, you'll probably have to use a taper tap, then finish with a bottoming tap.

The helicoil does have the advantage of being a smaller diameter. If your hole is close to an edge, that can be useful.

So Chris, do you think I should go the Heli coil route? I am pretty certain that somebody "helicoiled" all four bowl screws before, and thats probably why this happened. Maybe do the helicoil for now, then in the fall remove the carbs and have a machine shop drill and tap them

MT,
I am going to disagree with Chris on this application even though "he is never wrong" :) I have helicoiled at least 100 Holley carb fuel bowl screws and have never heard of one failing afterwards. If yours were helicoiled, and they pulled out, you should have a very hard stainless steel coil in your hand, that is what the Helicoils are made of.

I have helicoiled everything from Holley carb bowls to cylinder head bolt holes in blocks without a single repeat failure. There are other methods and some are every bit as good, but it depends on the application. There is not much room around the bolt holes that you have a problem with, and I dont know if a "solid" type insert would fit.

http://www.emhart.com/products/helicoil.asp

Just my opinion,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

After looking things over, I am going to guess that these bolts are not the original demon bolts. I remember my holley 800's threads were much finer.

It looks as if someone replaced the bolts with a coarse thread 1/4" allen socket bolt. The bolt only threads into the body maybe 1/4 if that. Im gonna guess this is why the threads pulled out.

What a mess. I think I am going to put in a heli-coil to match the coarse thread bolts for now, and after the season send the carbs out to BG or nickerson and have them rebuilt and redone correctly.

Thanks guys, appreciate it

I had 2 brand new out of the box BG's recently and they were both heli'd main body's, we noticed one was stripped even before it was installed, the wet flow chart was in the box with the shrink wrapped carb too... BG knows it's an issue, send it back to them, the inserts are a special length and thread

Hmm, thats good to know. I will call BG tomorrow and see what they say.

I agree that Helicoils are VERY reliable when done right. Had some holley float bowl threads strip once and couldn't get the special size helicoils in time. I found some 6mm bolts and threaded oversize for them. Worked perfectly after some clearance issues

Are the holes deep enough that longer bolts can reach good threads?