i have a edelbrock performer rpm intake and the heat crossover on both sides has ugly burn marks.is that common? im aware that the heat crossover can be blocked off.will blocking it off affect engine performance or anything else?advise needed.

 

Are you saying you have burn marks on the bare aluminum, or did you paint the intake? Burnt paint is common due to the exhaust heat. Burnt aluminum is not.

The crossover is there to help with fuel atomization when the engine is cold. What year engine are we talking about? There is usually a flapper valve in the driver's side exhaust manifold outlet that closes when the engine is cold to force the exhaust under the carb and out the other side. This valve is supposed to open when the engine is warm, but the bushings can seize. If it's stuck closed, you have a problem that needs to be fixed. Most of these valves are operated with a bimetallic spring, but the later motors use a vacuum actuated valve and a temp sensor on the intake.

 

yes the marks are on the bare aluminum manifold.its a 1969 350 and i dont have exhaust manifolds.i have headers.actually about 98% of my motor is aftermarket.i only have 400 miles on this rebuilt motor.