GUIDE : Helicoiling / replacing exhaust manifold studs

[JSeaman]

Courtesy of Mark3 on mkiiisupra.net:

1st off i plugged the induction passages with tissue, then i drilled the holes out to 10mm, i think the correct size is 10.4mm but i didnt have that size drill, better too small than too big a hole though, lol


then get cutting new threads for heli coils to go into using plenty of lubricant, i found using an 8mm socket and 12" extension and ratchet fitted to the tap to turn it made it easier to keep it going in square!




which leaves you with this nice new thread


Next find your helicoils, i used M10x2d (2d means there length is twice the diameter, so 20mm long) find your helicoild insertion tool and screw them in






when completely in they look like this


i didnt bother to snap off the insertion lug as it wasnt in the way of the stud.


Next the studs, i used M10x1.5mm hi tensile steel rod and cut them at 65mm long.




File off any rough edges so makking it easy to bite into the new thread


i installed mine with permanent thread lock


the finished item, 6 more to do and its sorted.




and its on, and all 7 locking nuts with flat washers torqued to 32lbft, 3 more than normal to overcome the courser pitch of the thread.


dont forget to use plenty of lubricant, degreeser before thread lock and a tin of compressed air comes in handy too for clearing out the holes completely

[suprarx7nut]

Good info. As a personal addition, double check that your tap is the correct size, regardless of whether it came in a kit or not. The tap must be a helicoiling tap. A regular tap does NOT work with helicoils.

[IJ.]

2 "issues" I can see

1: Hi tensile is neither needed nor desirable for the studs as something ductile is better able to cope with the heat and expansion.

2: Loctite in this area is useless as to remove a Loctited part you use heat.

[mark3]

Originally Posted by IJ.

2 "issues" I can see

1: Hi tensile is neither needed nor desirable for the studs as something ductile is better able to cope with the heat and expansion.

2: Loctite in this area is useless as to remove a Loctited part you use heat.

i was under the impresion the stock Toyota studs where hi tensile, so i followed suit! and if you ever intend to remove them at a later date, say after a few 1000 miles, mild steel will just sheer off when the nut rusts onto the stud.

as far as the thread lock goes it was more to stop the studs turning into the head when nuts tighted, just incase!!

[SwedishMeatball]

really nice guide.. but is it possible to do without removing the head from the car?

Cause ive had a BHG last year and just now my threads r giving up, not in the mood for removing it