During a recent road race track event, I lost compression/engine during a 4th gear pull. I removed the heads to find 16 bent valves, ok, broken timing chain. After pulling the timing cover, I found I had sheared the cam bolts between the gear and the cam. I know of others who have done the same, ironically, we all share the ASP underdrive pulley. I'm going to replace the damper with a ATI unit. Is there any other recommendations to overcome this problem?

 

Honestly I don't see how an underdrive pulley could have anything to do with shearing cam bolts?!

 

How did the cam retainer look? Did the shear, or unthread?

 

I think smaller dampers have a adverse affect with harmonics within the engine. The bolts were definately sheared, cut clean at the cam, and the shoulder left on the bolt head side was about the thickness of the cam gear.

 

Humm, interesting - a lot of ppl run the ASP w/o problems though. Are you sure you didn't over tighten the bolts?

 

My Z06 has about 12K on the odometer and 10K on the H/C. It is tracked for 20-30 minutes at a time at four times a day. I have only tracked it for about the last 2K of the 12k miles, that includes mainly street driving. I know street and drag racing quite well, road racing by far the most abuse a engine could ever endure.

 

There are some really good articles on the ATI web site about harmonics and their adverse affects. When I bought my ATI at Carlisle a couple of years ago, the guy that was there told me they couldn't get a 25% under drive to provide proper harmonic control and that is why they were only 10% under. Not sure if this is coincidence or not with the other cam bolt failure, but it is interesting. ATI also has a tech line, you could ask them the question.