Decide the best insurance against the dreaded " Crankbolt Failure" is to pin the crankshaft.Since GM won't fix it until it breaks ( which I realize may never happen) and I feel it could hurt resale an the car I'm gonna bite the bullet and do it.I've been told this is a far superior fix to the Diamond washer any negatives or drawbacks to doing this. Thanks.

 

It will weaken the crank a little I would think. I believe I would prefer a key way. Why not heat the balancer and use an arp bolt, I would think that would hold forever short of a supercharged application.

 

I think pinning is a great easy fix....the problem is getting to the parts...not a lot of room in that area. Good luck with it!

 

That is what people have been doing for years on supercharged cars !!!
GO for it !

 

I was told a drilling fixture is mounted to the front of the crank.A whole is then drilled through the crank and the pulley from the front so that its 50/50 split between the crank and the pulley.A pin is then driven in,its like a keyway after the fact.The washer and bolt secure it in place.It can't affect the balance because you remove metal and replace it with metal pin.Sounds like the factory should have done this from the beginning.Hardest part is removing the stearing rack.Tech said it takes about 3 hours.A special drill bit is also used since the steel is so hard.

 

Why are you even messing with it? If probably wouldn't happen to you anyway. I think the failure rate is less than 1 percent.

 

I'm just one of those"better safe than sorry people",wasn't really concerned until people with 10,12,13k miles had it happen to them nearly a year later.Really don't feel like taking a chance getting stranded when I can eliminate the possibility for a couple of hundred bucks.Besides if it does happen it can damage the end of the crankshaft,why take any chance even 1%.

 

That makes since, I was thinking a hole through the crank and pulley. I still think an arp bolt would hold fine.

 

Remember the saying, "If it ain't broke, fix it till it is." I think this would apply here. By the way, you will have to remove a lot of stuff to get to the crank to drill.

 

Not me one of those "Hot Rod Techs".

 

Pinning the crank is a smart idea, I think. If you are willing to do the preventive stuff now you will be able to sleep good at night. The fixture that we use comes from Magnacharger for their installs. Basically it's a round fixture with two holes in it. You bolt it up to the dampener and drill the holes. Don't spin the bit too fast, you will just hurt the bit's sharp edge. Then remove the fixture, clean out all the metal shaving. Put the two pins in and you are done. The factory bolts, I think are just fine. We use a lot of red locite for extra saftey. The factory tourqe specs are hard to get using hand tools. So we get as far as we can with the big breaker bar. Then use a impact to go the rest of the way. This is a hard place to get into on the car, but then again if you put a supercharger on you will have one step done.

Randy

 

By the way, I have seen many dampeners come lose before.
I have one of the 1% Mazada 323GTX cranks sitting in my personal garage and it sucks. No fun when they don't run!!!

Randy

 

Will magnacharger sell me the two pin set?

 

I think everything is for sale, for a price. That is the case in most businesses. Give them a call and ask.

Randy

 

Attempting to drill the crank with a portable drill, even with a drill fixture, is a really iffy proposition. The crank is incredibly hard. The only way crankshafts can be safely drilled is in a drill press, which means removing the crank. The risk of damaging the crank far outweighs the risk of failure.....just my 2 cents....

 

We've been doing this on C5's for a few years now in S/C and N/A applications. I've never seen or heard of a pinned pulley that failed. I've done it on a couple myself and it's a given if you're already in there for a S/C, H/C or something else. Considering the work required to access the crank/pulley to pin them, I'd take the opportunity to add something that would warrant needing it pinned to begin with. This is a very quick and easy task once the pulley and crank snout are exposed.

Here's the pinning tool that comes with the ATI Procharger. It consists of a piloted collar that fits in the pulley bore, a .253" drill bushing and a M16x2.0x100 mm allen head bolt. I understand they sell for ~$125 from one or more of the S/C distributors. I drew this up in CAD in case anyone ever wanted to make one themselves.





A couple of shots of pinning my buddy's crank/pulley when we installed his Procharger. The tool is inserted and the hole is drilled at moderate drill speed to protect the bit.



A 1/4" SS dowel is inserted in the hole which is deep enough to accept the entire length of the dowel. The installed crank bolt flange retains the dowel. Back then we were only putting one pin in but folks have since commonly been installing two 180 deg. apart for slightly better balance and twice the holding power although no one ever complained of imbalance problems with the single pin setups.

 

Patches,
That is the way we do it also. Same tool and everything!

Randy

 

Patches ,thankyou so much for the Pic's ,really clears the air and looks like a great method for insuring that the pulley can "never" come loose.Makes me think about a supercharger now!

 

I've had that steering rack out 3 times now. Its a pain in my tush. Yup, I lost a balancer. I wish I pinned mine while it was apart but I could not find the hardware.

 

Makes sense to pin it for a supercharger.

But for just an otherwise stock vette? The bulletin fixes the problem. If you have a dealer that won't do the bulletin because your's hasn't failed yet - pay them to do it. Then send the bill to GM.

If your willing to pay a couple hundred bucks for an aftermarket fix, pay for the factory fix and make them look ridiculous for not doing it in the first place. The rep sees where you paid the dealer to complete a bulletin, I'd like to hear how they are going to explain not reimbursing you.

Advantage to the factory fix - warranty. Not a concern on a supercharged piece, cause their warranty is out the window anyway.
But on a stocker, what if Murphies law bites you and something breaks.
Dealer sees you've been in there drilling and pinning, just gives them an excuse to blame the aftermarket mod.

I've even seen people sell their vettes because "someday the balancer might fall off." Get a grip. Find a way to make the dealer do the bulletin. Whether it's two hands to the head, or a couple hundred bucks, do the bulletin and problem solved.