This is another post about my age-old brake demon and figured I'd post a new one that gets to a particular matter to keep things simpler. I'm thinking one or more has the smarts on this pedal ratio thing. I converted from front drums to disks and manual to power. I gather that the pedal arm has two holes, one for manual and other is lower, supposedly for power brakes. Except that connecting the rod to the booster using the lower hole cocks it (rod) way off line so quickly nixed this staying with the hole it had been on since the fore and aft action for the rod is on alignment. I had to shorten the threaded rod substantially to bring the brake pedal down as it had been way high. There must be some geometry or maybe trig here that is involved and maybe shortening the rod created another problem with necessary rod travel. What's bugging me with all the hunting to fix the intermittent gremlin is never taking this into account with the install simply using the pedal as it was setup for manual brakes. My guess is the return travel is incomplete allowing the booster to stay partially activated...just a wild guess. Thanks.
Brake Pedal Ratio
- Thread starter Ron H
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You are missing the bellcrank linkage used on power brakes.
This is interesting; the SSBC conversion kit in my '63 has a dual booster that is a delco/GM pert sure and their ten pages of instructions say zilch about the pedal connection, and no parts, crank, etc. Came with a chitty eye bolt that I had a machine shop bud duplicate using decent metal. As mentioned, after shop install the pedal was comically high, easier to reach with my hand than jacking my leg up to press it. Shortening the threaded rod brought the pedal height to an inch or so higher than the gas pedal and return to turn off brake lights. Wild guess, is this booster didn't require a bell crank or woulda thought it would be in the kit. I'll have to look up GM boosters/rods. Another wild guess is the rod isn't fully retracting having shortened it allowing air seepage into the booster. The pedal intermittently sucks way down; but does not engage the brakes though the brake lights will come on. I can still push the pedal further and brakes work fine. I need to pull the pedal back up and there is a resistance like a sucking action to bring it back up. Booster vac checks show it works as it should. I'm watching another thread on this now as the guy has what sounds like the identical problem.
I gather the DB conversion system I have doesn't use a bell crank (mentioned in my #3 post). The 10 page install instructions say squat about the pedal hook up. Surprising since the pedal ratio seems like an important tidbit converting from manual to power. So there must be some other trick here to hunt down...
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