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Helicoil tap size

Posted: Tue Oct 25, 2016 6:23 pm
by AlanH
Just checking out my new Sprint auto and finding the usual abuse that always seems to be there.

Amongst other things, one of the holes in the inlet manifold for the thermostat housing bolts has been drilled out and tapped to take a 3/8 UNC bolt.

Would this take a 5/16 helicoil insert? I can buy them fairly cheaply but do not have a kit and would like to be sure that they fit.

If the worst comes to the worst I can put in an M8 (which I have) but it would be better to use the correct bolt.

Re: Helicoil tap size

Posted: Tue Oct 25, 2016 7:21 pm
by Mad Mart
The drill for a 5/16" helicoil is 21/64" (8.3mm.).

Re: Helicoil tap size

Posted: Wed Oct 26, 2016 4:23 pm
by RJF_70
AlanH wrote:Just checking out my new Sprint auto and finding the usual abuse that always seems to be there.

Amongst other things, one of the holes in the inlet manifold for the thermostat housing bolts has been drilled out and tapped to take a 3/8 UNC bolt.

Would this take a 5/16 helicoil insert? I can buy them fairly cheaply but do not have a kit and would like to be sure that they fit.

If the worst comes to the worst I can put in an M8 (which I have) but it would be better to use the correct bolt.
Did you part company with the 1850 then Alan?
Cheers Rich

Re: Helicoil tap size

Posted: Wed Oct 26, 2016 4:56 pm
by AlanH
Did you part company with the 1850 then Alan?
No, still got it.

Missed out on a very nice 1500 and decided to buy this. It was sort of a rebound purchase.

It drives really well but, as usual, things are crawling out of the woodwork (or dropping off the body).

As the saying goes - Marry in haste, repent at leisure.

Re: Helicoil tap size

Posted: Thu Oct 27, 2016 8:36 pm
by xvivalve
As another approach, I have several spare inlet manifolds lying around the place...