I do a fair amount of carburetors and see most every mistake that can be made to one. Stripping the bowl screw is a common one and the proper fix is more elusive than you'd think. Just like everything else in this sport, its always more complicated than it should be. The problem is that the screw is introduced thru the fuel bowl a couple inches away from the threaded hole and they must be perfectly in alignment. Thats the hard part. Heres my stuff to install helicoils, the tap and drill are holley items; the crank gizmo is an industrial inserting tool and well worth the price; the vise base to the left is modified to accept holley carbs. It works as well for the 4412 two barrells as all 4bbls This pic is the throttlebody being attached to the vise base. The throttlebody has to be held perfectly true to the drill bit, the vise base is how that is done. This is the drilling operation, the vise is firmly clamped to the deck (I can tell you from personal experience the soft zinc will grab and break a drill bit if you don't clamp it). You run the bit down until it bottoms out, don't force it. Then its over to the tapping machine. The tap is screwed into the socket that snaps into the machine. The vise base keeps the throttle body straight and true to the tap, you just crank the handle with some thread cutting oil in the hole. Run the tap down until it stops, don't force it. Now the tricky part. Getting the helicoil into the hole. You'll need to clean the shavings out as the oil will hold the chips in the hole. I use carb cleaner with the straw and wash the threads out under pressure. The helicoil is screwed onto the tool and the throttlebody is secure in the vise base. I've tried to use the inserting tool that comes in the helicoil kit, if you are down to your last helicoil this is the tool you want to use. You set the helicoil into the hole and crank with light pressure too muc pressure you distort the insert, it just takes a little. Run the crank down and you'll feel it tighten at the bottom. I use the longest available helicoils from McMaster-Carr and if you don't bump it a little they'll be out of the hole. It is safe to back the tool out for a looksee, you can run it back on down. The tool will bottom out, just give it another 1/2 turn and unscrew it. And there you have it, prettiest threads in the carb! Well, I had to put 3 helicoils in this one carb! Walking thru the pits I have seen guys with 3/8ths ratchets tightening the bowls. Looks like the other threads are pretty well abused too. Problem is I have just those 2 other helicoils and this is just carb 1 or 2 I have to have done for the guy for tomorrow. Tadah!! A nice little 950ish for a truck puller. And there you have it, how to put helicoils into a Holley for the fuel bowls. It is all about keeping everything straight and true so that screw will be able to pass thru the hole in the bowl and enter the threads a couple inches away.
Could you give me more details on your tapping setup? Is it powered or just turned by hand? I can't quite see the top of it in the picture you posted so I'm not sure how it's driven.
>>>proper fix is more elusive than you'd think>>> Impressive. But how about an improper fix? Might be less elusive. Fill the hole with JB Weld. Assemble. Dip in a greased screw. Let it set. Snug it up. Voila! Jack E/NJ
That little gizmo is worth its' weight in gold! I bought it ages ago from ENCO, it comes with that set of collets for 6-32 thru 5/8ths taps.
Thanks! This is great, We've got carb with a stripped bowl screw that we haven't had the courage to try fixing yet. Sent from my iPhone using Tapatalk
How much do you charge for a repair like this? Helicoils by themselves aren't very expensive, but all this work has to take a little more time than the normal "sloppy" install.
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