SO i have a 1980 Toyota pickup with a 20R i just recently installed a brand new remain crab onto it and now it seems to have the most illusive vacuum leak i have ever dealt with. it runs seeming alright when its cold, (choke closed but high idle) but when it warms up starts idling awful. sounds like a subaru with a intermittent misfire. it hardly runs and dies often. the mixture screw makes no difference in the way it runs. idle picks up when i close the choke slightly when warm cutting off airflow seems to mask the misfire a bit as well. i was pretty convinced that it was the gasket between the carb and the spacer or the spacer and the intake manifold itself.. but i have had the carb off 5-6 times attempting to reseal in with about every single gasket material known to man. but nothing seemed to improve or even change whatsoever. i have been looking for the vac leak with carb cleaner and spraying it right at the base of the carb on the valve cover side seems to make a pretty big change in idle. so i guess what im asking is there another large source of vacuum in that area? (minus the large vacuum line that runs from the base of the carb into the top of the valve cover) i have established that that is in fact not leaking. or a better solution for making an airtight seal to the intake manifold. i have searched all over looking for more specific answers but i cant really find any solutions to the problem and am starting to feel a bit hopeless, thanks.

 

Reman carb as in stock replacement, not a Weber? If so, what spacer is being used?

Spacer material is generally much weaker than what you're mounting it too, meaning it warps easy. If you have a Weber for example, a common failure point is the supplied adaptor.

There are hordes of vaccum plugs, caps and apparatus in that area if the truck is unmodified. The intake can also leak between the flange and head. Propane works well for tracing vacuum leaks.