HEMI Tech: Vacuum, Breathing and crank case pressure

I would use the lower pan as a baffle. It's there to make sure any oil flying off the lifters don't stream out the downdraft tube. I made an adapter for my 341 that takes a regular PC valve. I'm leaving the baffle in place to make sure that oil splashed up doesn't go up the valve. The benefit of the PC valve over the downdraft tube is that it can keep a vacuum in the block at idle and cruising. This will help not only in keeping the internals clean, but help keep oil from leaking out failing gaskets.

 

I am getting ready to install a Contrerras roller in my 341. It is a 282 X .475". The base circle is quite small compared to the stock cam which had only .330" Lift. He's right about the intake valve wear since the rocker drags across the top of the valve quite a bit. Even though I have adjustable rockers, I will be using hardened lash caps to help regain lost base circle diameter and help with the rocker arm geometry across the top of the intake valve. In this photo you can see the difference in the lobe base diameters.