The plenum bit is bieng cut off and I am fabricating a new box to fit a 28/36 weber. I was only playing around with the polishing today to see what she looks like. Next time round you will need glasses to look at it . If i dont get bored first.

Very nice. Can you polish one up for me?

Consider than you get more performance with a dual-hole plenum. But the stock B210/B310 insulator spacer will take care of that

Yea I am making up a spacer that has the dual holes in that will match up with my carb. Do you know what thickness is optimal and what size I should be making my plenum??

So it depends on your goals. For best driveability, use the stock 1/4-thick insulator so that the tube will sit close to the bottom of the plenum.

For maximum high-rpm HP an open plenum might be best, but I don't really know about high-rpm stuff. For drag racing engines they often use a 1" thick insulator to keep heat off the carb.

The newer Hitachi carbs have another insulating gasket and stainless screws between the throttle body and carb body. The goal is to keep the carb cool.