I pulled the intake from my '70 351C 4v last night and figured out where the vacuum leak was coming from. There is a tube that goes down into the valley from the top of the manifold, that used to be hooked up to the original carb (kind of a heat riser thingy)...I also found where the valley pan and the intake gaskets had seperated and was also leaking. So, now I have the new valley pan and gaskets and will be media blasting the intake today so I can get a coat of paint on it tonight after work and will re-install it tomorrow evening...so, only this question...on the "heat riser tube"...since I changed the carb to the Holley (it now has an electric choke)...does that heat riser tube need to stay hooked up? Does it go to any sensor inside the dash someplace or under the hood, or can I do away with it altogether and just plug the thing off? The gasket under it had turned to sh!t and was nothing more than a bunch of crusty rust and carbon deposit.