first question is about brake boosters...
can disconnecting the vacuum to the brake booster affect brake performance in any way other than increasing the efort required at the pedal? I am wanting to disconnect the booster, will this be the same as running no booster at all? I can't see why not myself

second question, on B310 sunny's and quite a lot of the later datsuns, there is a cast manifold thing under the brake master cylinder. It looks to be a tee for the front brake line, but the rear brake line goes in at the bottom and comes out further up on the other side of the casting. I have been told that this is a brake proportioning valve which reduces pressure to the rear brakes, can anyone confirm or correct this? I have converted to rear discs and am going to use a wilwood bias valve, and was thinking of bypassing this cast iron part altogether. Am I on the right track?
Cheers for any replies, I want to rally the sunny this weekend and I'm not happy with the brakes yet....

yes, and yes sounds like a propoortioning valve.

cheers Damon. I hate bad brakes. especially in forests

you gotta watch those trees, they jump out at ya when you least expect it.