vacuum leak!!

[bigbadchev84]

My brother just bought a 78 ford with a 400m the motor has been rebuilt. It has a vacuum leak that i cant get to stop underneath the carb on the drivers side. i have tried 3 different carbs and the all leak at the same spot when i spray starting fluid it revs up at the same spot everytime, on all 3 carbs. i know the other carbs are good, i took them off my other daily drivers. it has a 1/8" plate sandwiched between 2 gaskets, what is it for? it has a performer intake with an edelbrock carb. anyone have any ideas?

 

[ryoken]

pull it apart. check intake for cracks (unlikely). check your intake surfaces with a straight edge, i've seen them pull up the corners. if questionable, stuff paper towels in intake and drag a good med/fine flatfile across it. this will show you high spots in a couple passes. mill accordingly..

i like the roloc conditioning pads for gasket surface cleanup. fresh gasket, ya should be fine.. if its a thin plate, its probably there just for heat and can probably be pulled if questionable... hope that helps...

 

[diesel4me]

Plate might be needed

That 1/8 inch plate you mentioned is probably an adapter used to seal the gaps between a performer manifold and a square bore carb--many carbs base's dont "jive" with the weird shaped opening the performer intakes sometimes have,and need that plate sandwiched in there to seal off vacuum leaks--ford 2 barrel carbs used a phenolic plastic spacer plate on their stock manifolds that does much the same thing..

The Edelbrock carb has a dual bolt pattern--on a few intakes,I've noticed they also have the dual bolt pattern--on a few I've worked on,the holes were drilled all the way thru,allowing vacuum to leak out of the ones not occupied by a bolt--I think it was a previous owner that had drilled and tapped the holes out that drilled them all the way through,but who knows?--might be worth looking into if it seems to be leaking near the bolt holes..