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JBurer JBurer is offline
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Join Date: Nov 2008
Location: Austin, TX
Posts: 205
I agree with Paul's comment below on further investigation.

I took a drive with Don in this car a couple months before you purchased it. He was making in the 550rwhp area and we did several runs up to ludicrous speed. Car ran great and I know Don used the car daily for several months afterwards.

Assuming nobody played with your tuning map, and all of the fuel delivery components were functioning properly, I can only imagine detonation being caused by a differential in fuel quality. Here in Georgia, we use 93 octane (US Grade) fuel... I know Europe's numerical values for fuel equate to a lower knock rating, but don't recall the comparison past that. If the car were tuned for a higher fuel quality, your comments about ignition advance might be right on the lower quality fuel.

As your friend was driving the car while the damage occurred, it's hard to know for sure what happened. Are you positive the car was fully up to temp before your friend revv'ed it out? I seem to remember Don telling me he rebuilt the motor once in the past due to not letting the car get up to operating temp - if I remember the story correctly, in that incident he saw contact with the valves.

Regardless of the cause, I can attest to the car being in great working order when I saw the car here stateside.

Originally Posted by 911nut View Post
Look closely at the adjusting slots on the sprocket pictured. There's witness marks where it was in one position and is now indexed a few degrees.
Also, you can clearly see the contact between the broken piston and the valve. There's a crescent shaped indentation on the piston top which should be a dead giveaway. Furthermore, the valve is bent from the contact.
You need to ask yourself how it was that the previous owner was able to drive the car and never blow up the engine if it was truly was too lean.
Not arriving at the right root cause may cause you to rebuild your engine more than once.
Old 10-09-2011, 10:19 AM
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