Holley 600 Base Plate for Impco 425

[308RRC]

I have been using a Rochester base on my Impco 425 but want to change over to a 600 Holley. The pictures show the base plate I am going to use but I am not sure which ports I need to block.

[storm]

You don't, or shouldn't, need to block any ports. But you do need to block the hole that is smack bang on the middle of the baseplate between the 4 throttle blades. A Holley baseplate gasket will seal everything else.

[308RRC]

I have installed the 600 Holley baseplate onto the Impco 425. I blocked the hole in the middle and it is working ok, no vacuum leaks.