Helicoil Bell housing bolt holes or drill and tap for 7/16-13 advice

[thedave8]

As I progress with my swap, it Seems everything I got so far in my trade for an 833 for my perfectly functioning A518 is in need of help.....both shift forks were just slapped together in the wrong position, which I didn't even think was possible, the input shaft/ pilot surface was destroyed.....went ahead and just bought a rebuild kit from Brewers to ensure no more surprises
On to the bell housing, turns out all 4 bolt holes to attach trans to bell housing are totally stripped out......are you guys heli-coiling them or is it common to just drill big enough to tap for 7/16 inch bolts ....
Seems that would be an upgrade, the transmission holes are big enough....
Your thoughts?
Thanks guys

 

[Oldmanmopar]

Helicoil, We do many vintage street and dirt bike engines. The aluminum get old and porcity sets in, all holes are helicoiled whether they need it or not. we do the same for aluminum bell housings. Better to be safe. If you go to a larger bolt you have to make the trans or bracket hole larger. Why destroy 2 things when you can repair one

Also if the hole is that bad the the helicoil is loose. you can go to a thread insert.

 

[thedave8]

I see your point in that the heli coil provides steel threads where as if I just drill and tap for 7/16 I'd still be threading into aluminum threads
Side note, I wouldn't have to open up the holes in the transmission, I already test fitted and 7/16 fit

 

[Newbomb Turk]

Bellhousing bolts ARE 7/16. You’d need to drill and tap them to 1/2 inch and then the bolts won’t go through the transmission.

Heli coil or some other insert is a correct repair.

 

[RustyRatRod]

Helicoil, We do many vintage street and dirt bike engines. The aluminum get old and porcity sets in, all holes are helicoiled whether they need it or not. we do the same for aluminum bell housings. Better to be safe. If you go to a larger bolt you have to make the trans or bracket hole larger. Why destroy 2 things when you can repair one

Also if the hole is that bad the the helicoil is loose. you can go to a thread insert.

View attachment 1716523153

Heli coil, but use THAT KIND ^^^^ and not the BS chinsey coil spring kind. Those right there ^^^^ are the heavy duty versions and what you need THERE.

 

[thedave8]

Bellhousing bolts ARE 7/16. You’d need to drill and tap them to 1/2 inch and then the bolts won’t go through the transmission.

Heli coil or some other insert is a correct repair.

Sorry, I meant 1/2, I'll double check tomorrow

 

[bcschief]

Helicoil no Keenserts yes.

 

[junkyardhero]

skip the helicoil and go straight for a time-sert in this application.

if it's too blowed out for even that, then it's time for a visit to the machinist...

 

[Oldmanmopar]

Heli coild work great in aluminum. Been using the for many years. Some areas there isn't enough room for inserts. The thread spinning against the aluminum is what wears the threads out . Once you install a heli coil the bolt is wearing against the steel coil. Inserts can eventually loosen against the aluminum and want to turn out after a period of use. A coil has constant spring pressure against the aluminum thread.

And the hole in the trans cannot be a perfect fit . They are always a little loose because the bellhousing holes never align perfect with the transholes. I Already tightened three and went to start the 4 th and had to loosen the other three to move the trans to get it started. If you don't need and insert stay away and use the coil type unless the hole is to large.

Time serts are what we use in blocks for heads and mains. A time cert is installed and tightened with a threaded tool to expand them. Without much material around the hole you can do more damage then you repair if not careful.

The most important when using a coil is it has to be shorter then the hole even if it has and open bottom . Also it should always be installed lower then the surface.