Quote:
Originally Posted by Ol'Jim
I guess one might consider it a massive vacuum leak, but I believe it is un-avoidable with this car/engine. It is caused by a combination of the substantial valve overlap from the long-duration/high-lift camshaft I am running, (Solid/mechanical flat-tappet, Lift .637", Duration 312*/322*, (270* @ .050" lift). 13:1 Compression ratio. And an open plenum/single-plane high-rise intake manifold with a Holley 850 CFM Double-Pumper carb. Engines like this just don't build much vacuum. It is definitely not a street-driven car.
That is why I am thinking maybe I need to switch to a manual (Non-Power-Assist) Master Cylinder...  |
you must have good vacuum perhaps not a solid level but with little vacuum how is the fuel being sucked out of the carb ?
the brake booster vacuum line should have a check valve. the booster itself is a big tank to hold/smooth out the vacuum pulsations. the booster should have the higher vacuum with that check valve. if the check valve leaks/and or the booster leaks , then you won't.
placing your vacuum pump on the booster is a must do test with the proper components that do not leak. also checking all those vacuum lines for defects using the vacuum gauge and properly measuring for vacuum losses on each line including the carb vac operated pull offs..
its been a few decades since I messed with these vintage models but I also remember that the carb base gasket is also a big leak issue ..