Tim I would think under the conditions that you were using your engines even at those stock clearances this should not have happened, no long term WOT, general break in running, never should have seized a guide, It must have been a tighter clearance then that or some other condition. I'm sure your machinist will get to the bottom of it.

On a side note. I had a similar situation with a friends engine, turn out to be the wrong spring setup for the cam, self destructed at 4k.

Result ==$ 5,500

This was a short burst at 5200 maybe 10 seconds

See even more evidence that IF it ends up being the guide's fault it was tighter then the advertised clearance. Just my thoughts!

What was the timing? Number 7 cylinder? At 5200 I would think you were in the meat and potatoes of torque/ cylinder pressure. How about a picture of the piston? I highly doubt not enough valve guide clearance was the culprit.

No way it was guide clearance. One of the first sets I installed I ran it on the hose double checked everything, took the boat for a 10 min run, then the customer sent me a video of a 10+ mile run wfo at 5500. I didn't touch those guides. Check cam timing again and verify lifter and guide clearance.

[ATTACH=CONFIG]541409[/ATTACH][ATTACH=CONFIG]541410[/ATTACH]

According to bob the tq should peak around 4600, I was 11.8:1-12.2:1 the whole time was not lean I have widebands...

Tim, you detonated the piss out of the motor and it bent the intake valve over. Make sure you replace the intake valve in the cylinder next to it.

Whos to say the guide clearance wasnt simply too tight , from a quality control standpoint ? Without physically checking it, you're taking someone's word for it.

While it certainly may or may not be the root cause of the failure, I certainly wouldn't write "improper guide clearance " off as a possibility, because someone else ran Afr heads with no issues. They need to be checked imo plain and simple, as well as the valve jobs.

Exact reason why Id rather buy my heads bare, and have my machine shop assemble them.

How was I detonating with 12.2:1 and 32 degrees timing, i don't see detonation here