On an EA81 where the exhaust bolts to the head there are 4 holes in a square pattern.Two of them normally have exhaust studs in them.the other two are empty.It seems the two "normal" holes stripped out and took the studs with them,so Im going to rotate the mounting ears for the exhaust.My question is what size threads are those holes?And how long of a stud do I need?

My question is what size threads are those holes?

 

They should be 10 x 1.25.

 

My 76 had the same size as my Loyale / EA82s.

 

They screw into the head about 1/2 inch, maybe a little more. The studs I have are about 1 3/4 " long. I've seen slightly shorter & longer ones.

I tried with a set of M10X1.25 bolts that were 1 9/16" long.They were almost the exact height of the 1" ASV spacer and the mounting ear for the exhaust.So that means if it needs to thread into the head at least 1/2" they need to be 2" long.No wonder studs keep pulling out.less than 3/8" of fine thread in the heads...

I tried with a set of M10X1.25 bolts that were 1 9/16" long.

 

Yes, bolts would be all wrong. With a stud, there is full engagement of all the threads before any tension is built up by tightening the nut.

On an EA81 where the exhaust bolts to the head there are 4 holes in a square pattern.Two of them normally have exhaust studs in them.the other two are empty.It seems the two "normal" holes stripped out and took the studs with them,so Im going to rotate the mounting ears for the exhaust.My question is what size threads are those holes?And how long of a stud do I need?

 

This also depends if you have those "spacers" for the exhaust loop thingy..what ever... then you have two bolts that hold the spacer to the head and two studs that hold the exhaust up too the spacer. The bolts that bolt spacer too head are 10mm 1.25 x 25mm Metric Socket Head Cap Screw.

Studs are an easy comodity from the auto parts and can be cut too length if you wanted it shorter. I try too double nut the stud to prevent them from backing off but these cant be the heavy sized as they won't have sufficient clearance to rotate. Good luck..

so Im going to rotate the mounting ears for the exhaust.

 

That's just stupid. Go get a heli-coil kit. Leave the ghetto mechanicing in south america where it belongs.

 

GD

Yes, bolts would be all wrong. With a stud, there is full engagement of all the threads before any tension is built up by tightening the nut.

 

I've used bolts - if you do it right it's not that critical. What's important is to NEVER allow the weight of the pipe to hang from the studs/bolts/etc when installing or removing the y pipe. That's what does them in every time.

 

GD