70sgeek

Replaced the master/booster last year due to failed master and since then have had sticky brake pedal. Initially installed a new Master Power Brakes 9" dual diaphragm booster with 1-1/8" bore m/c (both brand new parts) for my disc/drum setup. The brakes hung up fairly noticeably and I had to pull the pedal up to release them from a stop. Even after that, sometimes after parking the car and turning it off the pedal still had to be pulled again to release the brake lights. MPB replaced the booster, advising they'd had some issues with a run of their 9" boosters that mine came from and that may have been the problem.

They swapped it for a new 8" booster, assuring me the smaller booster would still be plenty for my brake combo. It was ok for a few weeks but same conditions have now come back. thinking the m/c to booster pushrod was too long, I shimmed the master 1/8" away from the booster and that seems to have released the drag issue I had at idle - the car now rolls from a stop as it should, however the pedal still isn't returning all the way up from a stop. No immediately visible binding issue with the pedal assembly. .

I even installed a factory pedal return spring set-up (the clip/spring assembly that came on manual brake cars) but it hasn't helped.

Master seems fine, no bubbles or leak issues, prop valve is newer as well.

So I don't know for sure if it's a booster, master or vacuum issue (or any combination thereof) - Pedal has decent feel (not hard or spongy, stops well. Vacuum is supplied through a Leed Brakes electric pump for a solid 18+ psi vacuum feed, as on my best day engine vacuum runs between 16-18 on its own.

At this point thinking of either going back to a 9" dual booster or maybe a factory-sized 11" single and wanted to see some thoughts here as to which might be worth considering and what brands are of most interest? I've looked at Tuff Stuff, Right Stuff and CPP, whose 9" boosters are all essentially deemed universal. ( which I take to mean no guarantee I won' have the same pushrod issue as I seem to currently). The 11" Delco re-pops all appear to be non-USA items, not especially encouraging though they are fairly cheap ($103 for the non-Delco logo version)

thoughts as to the issues or suggested replacement parts if needed would be welcomed!

thanks

green1972

Steve Gregori restores original power brake boosters , and they last, the smaller booster is nice with a 455 giving room to easily remove valve cover and pushrods if needed Tim

https://www.brakeboosters.com/