Hi all,

I went to repair the threads on my bellhousing last night and have made a mistake. This bolt hole is one of the four that hold the bellhouse to the transmission. After drilling, tapping, and installing the heilcoil I inserted the bolt to check the fit and discovered it was at a noticeable angle, maybe 5-10 degrees.

I am unsure of the best way to proceed, but will start by drilling the heilcoil out bit by bit to try and protect the diameter of the hole. One of the guys on here had also recommended and threaded insert. Would it be possible to find one to fit in a odd sized hole with a 7/16 inner diameter? I may go to a machine shop for this one.

Paul

If you can pick out the end of the helicoil you can probably unwind it out of the hole with no drilling.

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--> Check out my FI Turbo build <--
--> And the race truck build project <--
--> The Diesel Corvette <--

If you don't have a drill press then you should farm out this job.

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Joshua

Hi Joshie and Procycle,

I have a Harbor Freight one, but I think the best thing is to see an expert at this point. I'm honestly not sure why my drill would have gone crooked, but it is only the second time I've used a heilcoil. As far as picking it out, I don't want to do any more damage to the bellhousing before someone looks at it.

Paul

Probably a wise decision

_________________
--> Check out my FI Turbo build <--
--> And the race truck build project <--
--> The Diesel Corvette <--

The drill may have been straight, but that doesn't mean the tap was also straight.

What you have to do to make sure the hole is tapped straight is: 1. Secure the work to the drill press table. 2. drill the hole 3. remove the drill from the chuck 4. insert a tap follower in the chuck 5. tap the hole using the tap follower to keep the tap plumb/square

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Joshua

+1
Left to its own devices a tap will try to start crooked every time.

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--> Check out my FI Turbo build <--
--> And the race truck build project <--
--> The Diesel Corvette <--

One day I hope to have a real shop. That said, I don't know if I can adequately express how utterly irritated I was last night.

I'm going to have a very expensive bell housing.

Paul

Take it to a machine shop and have them put a keensert in it.

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63 Plymouth Valiant Wagon

You should be able to unwind the helicoil to remove it. I would not try to drill it out as the stainless is likely to mess up the soft aluminum.
You can have the hole redrilled for a timesert, keensert or EZ lok. They are all much larger than a helicoil so the current hole shouldn't be a huge ordeal.
I'm pretty sure the helicoil drill for that bolt is 7/16" where as the EZ lok requires 3/4-10 tap.

As others noted, likely best to get it on a large drill press to straighten out the hole.
Best of luck.

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78' Volare - 225 Supersix
77' Volare - 225 Supersix

check out your local makerspace. mine has a reasonably well equipped machine shop