GeorgeS

I have a newly rebuilt 327. During the first 15 minutes of running I noticed a small burn mark on the Intake above #3 and #5. (the Chevy orange now has a nice black spot)
The black mark is about the size of a quarter. I was going to attached a picture but learned that I can't...

Any Ideas ?

c69vete

Sounds like the exhaust crossover. It happens if you do not block it off.

GeorgeS

Can blocking it cause a problem? What should I use to block it?

TimAT

With the intake installed it's a bit difficult, but if you can maybe slip a 2x2 piece of stainless steel between the intake gasket and the head by maybe loosening the intake bolts then you're golden. I'm not recommending that you do this, it's just a possibility. Blocking the heat crossover keeps the hot exhaust out of the intake, providing a little cooler fuel/air mix and also helps oil temp from the bottom of the intake. Other side is that the cold weather driveability may suffer a bit..

Durango_Boy

Yes, you can...

http://photos.imageevent.com/durango...g%20Images.pdf