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MG MGB GT V8 Factory Originals Technical - Oh no oh no oh no OH NO I stripped the threads!!!

I think I may have stripped my distributor hold-down threads!!! There is a steel bolt but I fear the threads are just aluminum (Rover 3.9). I think I simply forgot when tightening that we were talking aluminum block, and I felt that sickening lurch of the ratchet. Is there any way to repair the threads without yanking the engine out of the car?!?
Mike

Hello Mike,
Good and bad news. You can install a Heli-coil insert into the block. This is a steel spiral that replaces the ripped out threads in the block. If done properly it is stronger than the original alu threads. You will have to bore the old ripped hole out. All this is better done by a professional mechanic but if you are a handy man you might tackle this job also. Good advice. Try one in a mock up. or dummy hole in an old piece of aluminum.
Talk to a good mechanic. He will help you out.
Many alu heads already have heli-coils installed from the factory out for the spark plug holes.
Good luck with the repair!
Next time, use a torque wrench with the proper settings to torque your head onto the block.
Werner
werner Van Claodurp

Werner, have done heli-coils before, no real problem. But my guess is that in this case, a lot would have to be disassembled before sticking a drill in there, no? You wouldn't want a bunch of swarf to drop down into those distributor drive gears, surely?!? I'm not near the car now, but it seems to me this hole is on the timing cover, so I guess I'd have to take the timing cover off before doing this? Now that's just gotta be one heck of a pain in the rear with the motor in place.
Mike

I seem to remember an epoxy repair kit. You basically fill the hole with epoxy and then push the bolt in place.

I can't remember who sells it. Just about any hardware store will sell metal epoxy, that may be worth a try, although i'm not sure how you would keep it from sticking to the bolt as well
Michael Hartwig

You do have a few options, depending on how creative you are. The main problem is to keep shavings out of the engine. This could be done by pulling the distributor, making a vacuum cleaner nozzle that will fit through the hole and reach under the hold-down hole and catch anything that falls through. If done well it can catch everything. (remove the breather so you get some draft) I do not recommend the epoxy. You stripped the aluminum and epoxy is weaker than that. Harsh words I know, but practical too. Heli-coil is good and stronger too, but requires drilling and tapping. Third option is tapping for 3/8-16. The tap drill is 5/16 so no drilling is required. The hole in the bracket would have to be enlarged.
Jim Blackwood

you can use an epoxy thread repair kit to repair/make threads if you don't want to use a heli-coil repair. It works well and easily strong enough to hold down a distributor. Otherwise you'll have to do a carefull and slow helicoil without removing part.
Joaquin

Mike..just a thought having been in this situation. first blow out the hole and then try running a a bottoming tap down the hole. due to manf methods very often they do not tap down to the bottom of the hole as this would lead to too many scrapped parts due to tap breakages. you may as i have done be able to tap the hole deeper.
regards adrian
adrian salisbury

you could even glue the distributor in position but if you tap it, you don't want any swarf inside the timing case.

Two options; either a,remove sump Wash out swarf with flushing oil - collect at the bottom of the timing cover or b, remove alternator, rad, crank pulley and timing cover so that you can work on a bench.

The advatage of b, is that you get to replace your timing chain.

Hope this helps
Roger Walker

How about getting an appropriately-sized stud with nice new threads, screwing it into the hold-down bolt hole with some epoxy thread repair, and using a nut and washer after it sets up.

Wayne
Wayne Pearson

It can be heliarc welded and then redrilled and tapped, that is a premanent solution and a major advantage of aluminum over cast iron blocks (besides the weight advantage)
Michael S. Domanowski

If you go the epoxy repair route, spray the bolt with PAM cooking oil spray. Shake off the excess. We do it in the boat construction business all the time. You want to brush the epoxy into the threads of the bolt so you don't get air bubbles, which frequently happens, especially with thickened epoxies. Make sure that you thoroughly degrease the hole, as you do want the epocxy to stick there. If it doesn't work, epoxy is easy to drill and then go the helicoil route. Might hold until you remove the timing cover for some other reason, such as replacing the chain as was mentioned. Heli coil still probably best, though. Jim blackwood's vacuum attachment would definitely be worth checking out.

Best regards, David Walworth
David Walworth

purchase a stainless steel stud of the correct size, install it with blue locktite, tightening it hand tight. Run a tap through a new nut so the threads are certain to be good. install the hold down 24 hours later. This assumes you have some good threads left in the timing cover.

If the timing cover threads are completely shot, use a stud with Locktite Form-a-thread, pn 81668. For a 5//16" bolt, the max torque after 24 hours cure time is 16 lbs. The advantage of a stud over a bolt is that you can use more torque on the nut than you could use on a bolt. The stud is being pulled straight up with the load spred evenly over all the threads. Not so with a rotating object.

Not sure about the early motors, but the later Rover engines came with studs & nuts in place of bolts at this location.
Jim Stuart

Thanks for the tips. I ordered a SS stud from Summit (for SB Chevy, BTW) and fixed it in there with a dab of good old JB Weld (the stuff has never let me down). There were plenty of threads left to allow the stud to be tightened in there decently. Waited a few hours, put on the pinch bolt, and we are off to the races once again. I now realize that the pinch bolt need not be particularly tight just to hold the distributor from rotating. Phew ... got away with this one.
Mike

I STRIPPED THE same HOLE AND A valvecover HOLE.................
JUST FIND THE SLIGHTLY LARGER TAP OVER .250 (A 7mm X 1.25 or 1.5).......about .280"

PULL THE DISTRIBUTOR, CRAM A DAMP OILY RAG INTO THE HOLE TO CATCH ANY CHIPS
AND TAP AWAY YOUR PROBLEM. I use discretion now on tightening things and not in such
a hurry. C U ON THE ROAD..........
PAUL

This thread was discussed between 07/05/2001 and 23/05/2001

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