I replaced the gaskets on the rear carb, as the spacer/gasket between the throttle plate and carb was apparently leaking, causing an air leak, and I think that had part to do with why it would die when putting it in gear. Now it sometimes goes into gear. If I spray carb cleaner around the rear carb, it still revs up a little bit, but I have replaced every gaskets, and every bolt/screw is tight. I am not sure what else I can do??

When the car is at idle, if I block the rear carb's idle air bore, the car revs up. When the car does go into gear, it runs fairly rough. If I block that rear idle air bore, it runs good. I don't necessarily think it has to do with the idle circuit, but I'm sure this bit of info is telling me the problem but I just can't figure it out!

Last question, on the Zeniths, are both carbs supposed to have the same gaskets throughout? Particularly the uppermost gasket. I assume so, but just double checking.