Engine speeds up when brake is pushed

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gunmetal72

gunmetal72

Life is a dark ride
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I am not sure what is going on so thought i would ask all you smart guys on FABO. With power brakes, I thought when you push the brake pedal with the engine running, the engine will drop 1 or 2 hundred RPM's. But when I push the brakes the engine speeds up. Any ideas why??
I should add (just in case it's related) that I am having some issues with the brakes having not enough vacume to the brake booster due to the cam that was installed.
 
Well your having a tuning issue, use a vacume gauge to tune your car, start with adjusting valves if they are adjustable. then set float levels, then tighten idle mixture screws till they stop counting the turns as you go then back them out equal amounts of turns for a "Happy Medium" Now that you have done that hook up a vacume gauge to direct vacume and adjust idle mixture screw till the vacume reading gets higher then match the oter side same amount of turn that you did to the first one to increase the vacume (keep these screws equal amount of turns) when you have achieved your mhighest vacume reading you can proceed to set the timing....I do NOT own a timing light....never have...never will but...I do like them ones with the dial on em....they are neat to see what ya got...I will rev the warmed engine to about 2500 rpm's and adjust the timing by ear listening for the engine to labor then switching the direction I was turning the distributor and turning it ever so slowly listen for the sweet spot where she doesn't have a miss or seem to be laboring. then I will reset the engine idle speed and shut her down.....after about two minutes I will hit the key to start her up and if I hear the starter motor labor I will retard the timing a miniscule amount, restart the engine and run for a little bit and repeat the process till she fires properly...there may be others chime in with diffrent methods....
 
The valves are hydraulic so I can't adjust. I changed the carb to a edelbrock and never touched the floats, not sure when they should be or how to adjust. Would I hook up the vacume gauge to the large hole at the base carb, and how many lbs of vacume should I have, or am I just trying to get it as high as I can by adjusting the air mixture screws.
 
What cracked said, ya got a big old vacuum leak it's either that or you've just re-wrote one of the basic laws of Physics.:D
 
Probably the only one this has happened to... but I was having the same issue and found that when I was hitting the brakes the edge of my big a$$ foot was catching the gas pedal.
:banghead:
 
Clamp the line to the brakes. Do a SLOW test drive.
 
I tried to reseal the booster by cleaning the rubber using a little urathane on the gaskets, the one under the big clamp on the booster and where the master bolts to the booster. No Difference. Is there a someplace that would rebuild the booster or should I take it off and go a different route?
 
I agree with everyone else, the booster is shot. If your gonna continue to run a cam that has 10-11" or less of vacuum when properly tuned you might want to consider doing away with the vacuum assist. If you want to keep it power you can always add a canister that stores vacuum when you decelerate so it's available when you need it. Even if you took that route i would still look into replacing the booster.

P.S. When boosters go, it's internal. You wont be able to seal it up.
 
Ok, I guess i will start looking for another booster. I like the power brakes and I can always add a canister for additional vacume. Anyone know if anyone has a good used one or where i can buy new?
 
You don't state the car year or model (72?). A photo of your booster would help. Since you mention a clamp, it sounds like the same basic model on my 65 Newport (Kelsey, I recall). Don't fear taking it apart, it is very simple inside. My diaphragm had a hole where the vacuum port enters (gas vapors). I couldn't find a rebuild kit or diaphragm anywhere, so cut my own out of neoprene rubber and secured the inner edge in the welded plates w/ flowable silicone. It works when tested w/ manifold vacuum, but I haven't installed (replaced w/ one from a 74 Dart, drilled new holes).

There is one rebuilder recommended on hot rod sites - "Booster Dewey" I recall. I probably have the link at home.
 
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