FRDnemesis

iTrader: (19)

I have an Aluminum flywheel from Company "X", and it has only been in the car for 3.5 months (3k miles) and has never been raced. Well, recently my car spun a rod bearing and I had to remove the motor. When I removed the PP bolts, 3 of them came out with the threads attached to them. They were only torqued to the recommended 55 ft/lb.

I called company "X" and they don't have any more aluminum flywheels readily available so they wanted me to send them mine so they could Heli-coil it. I mentioned I could do that myself, since we have a state of the art machine shop here in the company I work for.

So I went and purchased a heli-coil kit, and took it to the machine shop. They didnt really want to do it because they say the coils may not hold in the aluminum permanently because of the direct pressure being applied when the clutch pedal is pushed in. Well, if they are correct, we all know what a flying clutch could do at 7k RPM.

I guess what I'm looking for is a second opinion, so blast away with some insight.

Thanks,
Jeff

daryl2cb@yahoo.com

iTrader: (2)

I would think you could just go up a size in bolts and retap the holes, I am not sure if this would hold any better than the helicoil though, just line the PP up with the pins, if you flywheel has pins. other thing you could do, depending on clearances would be to stud the flywheel, I do not know if this has ever been done, but it might be another option.

FRDnemesis

iTrader: (19)

I know that McLeod studs their flywheels on the Street Twins, but they cut the backside of the flywhee to recess the head of the bolt.

DONAIMIAN

iTrader: (18)

I agree, I would just go up a bolt size. See what ARP has to offer you.

bilt2rev

You could also try a Time-Sert. http://www.timesert.com/index.html. Threads will be better than new.

SUTTERERMAN85

iTrader: (42)

i used these in a 97 Northstar Caddy my old man has. works great on ALum. the head bolts have a tendecy to stip on those motors.

FRDnemesis

iTrader: (19)

I have NEVER seen or heard of those before Definitely something to consider I suppose. I saw the vendor list, but is there anyone of our vendors that sell them??? Where did you get them?

Thanks,
Jeff

bilt2rev

Try this place.http://www.fastenal.com/. They have locations in SC.

Josh

BJM

iTrader: (1)

With all due respect to your machine shop they do not know what they are saying. Read the technical data at the Heli-coil site (Click Heli-Coil at the top). I have one of their catalogues in front of me and it clearly explains how they work. In your case, the aluminum is the weak link, the fastener is way stronger than the aluminum.

Typically full strength is reached after 3 full threads of engagement are reached with a normal metal fastener. The Heli-coil increases strength 2 ways. The heli-coil, being a flexible member between the bolt and hole threads increases the effective number of loaded threads increasing the pull-out strength. In addition because the effective shear diameter in the aluminum is now larger than without the Heli-coil, the pull-out strength increases more. Military/Space and aeronautical applications routinely use heli-coils in aluminum parts.

You can step up even further and use a Keensert (at this page), its basically a slug with internal and external threads and can be used to step up the outer diameter until the stress in the aluminum threads is reduced to a much lower level since the thread area increases with the OD of the insert.

FRDnemesis

iTrader: (19)

I called Peter Wednesday night in Australia and spoke with him. He said he didnt have any Aluminum Flywheels in the US to replace mine with so he mentioned something about sending mine back to him so he could heli-coil it.

I mentioned to Peter, that I could have that done here (posted in my original post above). He said that was great, and if I still didnt feel comfortable with it after it was completed to let him know and we could get a new balanced unit (PP, disc, fW) swapped out.

He sent me a PM on Thursday and I replied; stating that I didnt feel comfortable with the heli-coiling after what my machine shop said, not to mention the cracking on the mating surface. I havent heard back but at this point, I'm putting my stock unit in the car, just to drive back and forth to work.

So if you could help expedite this process I'd greatly appreciate it. I have pulled my bank records as you requested and have the purchase date. I never did get an invoice with the setup.

Thanks,
Jeff