Leaking exhaust valve; 10k after rebuild.

[Frozen240]

I had the engine rebuilt by a machine shop about 10k ago. I left the valve train components stock but the valves were ground and the seals were replaced. The stock valvetrain was all in spec, not too shabby after 200k (we're talking kilometers, not miles).

Recently, I had noticed oil pooling on the top of the exhaust manifold on cyl#1 and thought that it was weeping out of the valve cover gasket. I removed the exhaust mani and found the #1 exhaust valve leaking oil into the cylinder.

Is this a cooling problem? I just recently installed an oil cooler, but the any benefit that this would have served would be negligible for the short amount of time that it was on the car.

Should I upgrade the exhaust valves, ie Ferrea or Supertech. Valves that are made of different material than the stockers and are designed for turbo applications. I would like to stay with the stock size regardless.

Is it possible that the machine shop screwed up? I would imagine that if it had been their fault, it would have shown up a lot sooner. I am planning to take the head back to the same shop to get the work done.

Is anyone else burning up their exhaust valves? I read the forums regularly, and I haven't come across many much info on valves.

[rotorimp]

Of the 1000 variables that can cause a stem seal leak it is most likely that the guy installing it didn't catch a tear in the seal or there was a burr on the guide from reaming---and it took 10k to finially show up

[Frozen240]

Allright, so I have the head ripped off and I'm taking it to the machine shop to get it checked out. I think that i will be upgrading the valves to either a Ferrea or Supertech.

Should I go with a larger size or stay at the same diameter? Is it an expensive proposition to machine the seat to fit the larger valve? What are the limitations associated with grinding the seats?

[WDRacing]

There's no need to go with larger valves. But there aren't any bad issues with having the head work done that I know of.

WD

[C-Kwik]

Your valve stem seal may be bad. If you have the right tools, replacing this seal should not require the head to be removed. The guides could also be worn as well, but simply replacing the valves is not a solution. Before buying more parts and spending money, determine where the leak is actually occurring.

[Frozen240]

Turns out that the guides are worn. Exhaust side only, the intakes are fine. They were replaced with oem spec cast iron guides. When the work was completed on the head, everything was within the specified clearances.

I'm going to try using a bronze guide instead. It should have better heat transfer characteristics and the tolerances can be tighter than a cast iron guide. Anybody else running bronze guides?

Here's an informative article on valves FYI.

http://www.aa1car.com/library/ar696.htm