Worried, 1 white exhaust valve!

[ArthurRAiken]

Tonight I was unbolting the manifolds off my '87 383 project ram and found that the #7 exhaust valve was paper white. All the rest were a dark charcoal color as expected. I need to hear some responses about why one cylinder would go lean and not notice any detination.

The motor is still in the truck.
It has only about 2000 on a rebuild.
I've only used 93 octane since the motor was built.
The #7 spark plug appears to be normal.
Compression ratio is between 8.5-9.0
Carter AFB 600 unchange from the factory.

I've been having fuel problems since I built the motor. It idles at 5lbs of vacume when hot and the exhaust fumes will make your eyes water. I really haven't had time to mess aroud with it till now.

I will be bolting up a new set of "thorley" headers tomarrow. (btw, the thorley's that I got are in just as bad a shape as those who have previously posted. They look as though they didn't prep them before they coated them.)

Thankyou for your replies,

Arthur

[Stoga]

One thing I would do, is spray some penetrant or carb cleaner around the ends of the intake manifold when idling. If the idle changes any at all, you have a vacuum leak, which I suspect from the symptoms you describe. This will also help show you the location of the leak.
Also, if the carb was adjusted with a vacuum leak present, you would have all the other cylinders rich just to get the one lean (vacuum leaking) cylinder to fire. I don't know if there is anything wrong with the steel shim intake gasket, but sometimes they need a little sealant to seal up all the way. Something has to be making that one cylinder lean enough to whiten the exhaust valve, and the intake gasket would seem the most likely culprit. Good luck, and let us know what you find.

[ArthurRAiken]

Thank you stoga for your quick response. I never thought about a vacuum leak comming form the intake. I used a new gasget and plenty of sealent, but that would make perfect sence, like you explained. Thank you for the heads up and I'll let you know how things go.