Due to the time the valves stay open on the ‘big’ cams, vacuum is low and therefore you can’t get enough of it so the vacuum booster will not operate to its fullest extent.
Putting a big diameter booster under the floor in my experience is ten pounds of booster in a five pound hole’. If you have the room for a large booster fine, I never did. I had to go with a 8” made for a Mustang, if I remember correctly. That didn’t work well so I ended up with one of those ‘pancake’ types.
All in all, I believe my problems boil down to one issue..pedal ratio. Due to using the orginial pedal setup, which was drum/drum and no booster (39year). The long ‘throw’ on the pedal above the swivel pin and the short distance the brake rod moves is my root problem. If you have the same problem then get ready for a lot of pedal movement before the brakes start to work. The adjustment of the rod between the booster and master cylinder will be critical.
I just read Jerry response. He is correct if the vacuum produced by the engine is your problem. I would call the cam manufacturer and ask about the cam you want in you engine and the vacuum you can expect. The canister is a good idea. You know what will/will not fit so build/buy to that spec. Bigger is better.
Good luck in you quest.
Thanks, I appreciate the advice!
