Pressure Plate to Fly Wheel Heli-Coil?

[Lloyd]

Ive got my engine together then pulled the original one and took off the bell housing and flywheel to put on the new engine.

One of the bolt holes on the fly wheel that holds the pressure plate on has some really bad threads, putting a bolt in does not need turning - just wiggle it some. When I took the pressure plate off there was no bolt at all in this hole. I tried putting a tap in it but it practically falls thru. I'm guessing the original bolt vibrated loose and tore up the threads in the process but not sure what happened. The bolt was not in the inspection cover. Will a heli-coil work on this? Ive used them before but never on something that would be vibrating as much as a flywheel. Kinda stuck but I would like to make certain I get all the bolts in. Only other real option is try and find another flywheel.

 

[William Davey]

I don't have any direct experience with heli-coils in a flywheel, but a buddy used them all the time for the spark plugs on a drag racing Harley Davidson.  The bike had very high compression blew the steel spark plugs out of the aluminum cylinder heads.  That thing vibrated worse than any car or motorcycle engine I've ever seen.  At one time, it was the fastest gasoline powered Harley in the US.  I can't imagine your pressure plate application puts any more stress on the heli-coil.  I think they usually are held in with red Locktite.

[Lloyd]

Hey William, thanks. Yeah I would imagine that machine vibrated quite a bit. Your buddy used the lock-tite on the heli coil insert or the spark plug? I never used anything on the insert, never really thought of it.

[dlrides]

Have a machine shop re-drill the flywheel and balance.

[Lloyd]

• Yep, that would be the best option. Save guesswork and hoping it works.

Thanks.

[builtfercomfort]

Would a slightly larger metric size work? Drill/ tap- bolt and be done? Or is it not that simple?

[Don Coatney]

Adding one metric bolt will cause problems for the next guy who works on the clutch. I would not do it.

[Lloyd]

Thanks for the input Don. You would have to color code it to make sure you put it back in the right hole.

 

While using one metric bolt may be an option and might even work I think dlrides had the right suggestion. I will be taking the flywheel to the machine shop and getting them to redrill and balance it - got to get it re-surfaced anyway for a new clutch and pressure plate.

Bottom line is any modification to the flywheel will require re-balancing.