Thread: Maybe solved the mystery of the bent valves

To recap, I have been preparing a pair of new heads that have done only 15KK before being removed.

After cleaning up the valves , I went to grind them in and found an inlet and exhaust were bent on one cylinder.

I wracked my brains trying to work out how, and I now recall I had a dyno tune done with the heads on.

I reckon that the tuner who shall remain nameless overrevved it. It's the only explanation I can think of as plausible.

I have decided not to have the valves recut as they have really good witness marks ( after replacing 2 valves) and the head has only done 15KK.
BTW someone suggested a three angle valve job. I now recall that when I had my 3.9 heads prepped by what I think is a good shop, they told me that there was not enough room in the seats to do it.

I remembered this when I was cleaning up this head, and noted that there is less than 1MM from the edge of the seal area on the valve seat to the inner edge. I believe that you would need to have a bigger valve in the existing seat to be able to reangle the throat on both the inlet and exhaust. unless you made teh seat area on the valve much narrower, which is undesirable in a touring engine.
I would be interested to hear of anyone who has done a 3 or 5 angle seat on Rover V8 3.9-4.6 heads as it doesn't seem possible without bigger valves.
Regards Philip A

plenty of room for a 3 angle cut on pretty much every engine, it just comes down to the skill of the guy doing the work and the tooling he has available.

I generally don't bother doing a proper 3 angle job as a, I don't have the gear b, usually if Im getting headwork done its just as cost effective to get the place thats doing the head machine to do the valves.