Slant Six Forum
https://slantsix.org/forum/

Torque contertor holes.
https://slantsix.org/forum/viewtopic.php?t=53988		 Page 1 of 1
Author:  Rick Covalt [ Mon Dec 02, 2013 7:00 am ]
Post subject:  Torque contertor holes.
Has anyone drilled and tapped their torque convertor bolt holes where the flex plate bolts up to a bigger size. Mine has the 5/16 fine bolts in it and they have come loose a couple times. But the real reason I was considering going to 3/8" is that the flex plate holes are almost that large already. And the 5/16 bolts have plenty of room to flop around. It looks to me that a slightly larger bolt would be a better fit and may aid in them not loosening. Is there any reason not to do this.
Rick
Author:  hantayo13 [ Mon Dec 02, 2013 10:53 am ]
Post subject: 
use grade 8 fine thread..... don't see why not
Author:  Exner Geek [ Mon Dec 02, 2013 6:57 pm ]
Post subject: 
I had an altered stock type converter once that had this done. The threads eventually failed, I believe it was because a 5/16" hole is too big to cut proper 3/8" threads. I found a table that shows that a 3/8-24 thread takes a Q drill, unfortunately I don't know what diameter Q is. You run into a similar problem if you try to re tap 7/16" head bolt holes for 1/2" studs. If there is enough metal in the lugs it might be possible to put in 3/8" fine helicoils.
Author:  Rick Covalt [ Mon Dec 02, 2013 7:14 pm ]
Post subject: 
Thanks Seymour that is good info.

Rick
Author:  Pierre [ Mon Dec 02, 2013 8:40 pm ]
Post subject: 
I went through this years ago but in reverse, trying to find a flexplate with smaller holes. I think at one point I had a bushing made even but never used them. Came to realize bolts were loosening because whomever had assembled the trans/motor back together didn't think those locating dowels were necessary.

Moral of the story, if they loosen somethings amiss, and its not the size of the holes and/or bolts in the flexplate. If the bolt head's clamping on the plate properly the flexplate won't move. Are you using generic hardware store bolts? I believe their head is a smidge smaller

If you insist on going to bigger bolts, I wouldn't use a helicoil just drill to the required size and tap. The last time I remember handling a converter, the lugs didn't have much extra meat around and a helicoil would only require even more being removed, risking cracking the lug. You'll also need a bottoming tap as there's not much room between the lug and converter.
Author:  Rick Covalt [ Tue Dec 03, 2013 10:30 am ]
Post subject: 
Quote:
if they loosen somethings amiss, and its not the size of the holes and/or bolts in the flexplate.
Quote:

Maybe, but many, many of those who are racers have had them come loose.

I personally have used both factory and longer Grade 8 fasteners. The last ones did not come loose but that was only after about 8 or 10 runs down the strip.

The underside of the factory bolts has a very small face surface and if the flex plate has larger holes than needed, I am not sure that the face of the bolt is hitting anything on the one side.

The convertor is an aftermarket one and looks to have plenty of meat to re-tap larger. I could not find any locking hardware for theses small bolts.
Author:  slantzilla [ Tue Dec 03, 2013 11:13 am ]
Post subject: 
Performance converters are tapped for 7/16" fine thread. You should be able to redrill and tap your 5/16" holes for that. You will probably also have to tweak the holes in the flexplate. I'd use a good step drill bit. :D
Author:  Pierre [ Tue Dec 03, 2013 12:12 pm ]
Post subject: 
ARP 12pt flexplate bolts seem to have bigger heads on them.

Safety wire? Those heads are awfully thin to drill though.
Page 1 of 1 All times are UTC-07:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/