I have seen two different arrangements for gaskets with the 1972 351 Cleveland (2V heads). One does not use a valley pan and has two thick head side gaskets with cork end pieces. The other comes with a valley pan and uses very thin paper type head side gaskets with rubber end pieces. I'm confused... Should it be using a valley pan or not? Any disadvandtages/advantages to the valley pan?
The Cleveland engines have an intake manifold that has an area that runs in under the carby area that taps into the exhaust so that some heat from the exhaust helps to improve running when the engine is cold and the auto choke taps into it with the original carby. It heats an area around where the carby is bolted. You will see the ports for it on the intake face if the manifold is an original. The valley pan is to stop oil splashing onto this heated area and vaporising causing oil usuage.
Not using the valley pan doesn't generally cause many problems and alot don't bother with it but I usually use it.
I couldn't get my engine to idle/run properly until I installed an inlet tray. It helped overcome a persistent vacuum leak that wouldnt go away even after milling the manifold faces. Now all is good, finally.