When re-installing an intake manifold with EGR valve blocked off, is there any reason or benefit to also block the exhaust route from the heads that crosses through the intake manifold? This is the area of the intake gasket that sometimes has the metal restrictors. Will this affect fuel air temp? Will it cause any problem in the heads? How about engine temp?



|UPDATED|6/14/2004 5:23:55 AM (AZT)|/UPDATED|

Not really. As long as the exhaust is intact and the engine is running correctly, it won't bother it one way or another on a warm engine. Equal pressure on both sides of the engine cause exhaust not to flow through the intake. If there is unequal pressure it does flow.

Which bring us to the heat riser on the right side of the engine. Early ones are just bi-metallic spring control, newer ones are vacuum pot controlled. They close when the engine is cold, and open when warm. The closed flap creates more pressure on one side of the engine, so exhaust does flow throught the intake. This is designed to heat the intake on a cold motor, which heats the air and fuel. The result is quicker warm up and better cold throttle response. If you block the passage you will loose this. If your heat riser is stuck open or has been removed it won't matter.
If the heat riser is intact, or you want it to be later, leave the passage open.

Thanks Ken!