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#1
02-02-2005, 07:31 AM
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Have a 68 Pontiac F/B conv w/455 .060 over. #62 heads, RAIV cam, headman headers peformer manifold, quadrajet carb. TH400 trans, 3:08 open rear (hopefully to be changed soon). Problem is the brakes sometimes don't work !!!! (power drums) I've adjusted them and bled them but I have to put the car in neutral and rev the motor to get enough pedal for the brakes to grab. Otherwise it's hang on and aim for something soft. I've checked for vacuum leaks and couldn't find any. Thinking about taking the anchor off my boat and keeping it with me.
Thanks in advance. Roy |
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#2
02-02-2005, 07:31 AM
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Have a 68 Pontiac F/B conv w/455 .060 over. #62 heads, RAIV cam, headman headers peformer manifold, quadrajet carb. TH400 trans, 3:08 open rear (hopefully to be changed soon). Problem is the brakes sometimes don't work !!!! (power drums) I've adjusted them and bled them but I have to put the car in neutral and rev the motor to get enough pedal for the brakes to grab. Otherwise it's hang on and aim for something soft. I've checked for vacuum leaks and couldn't find any. Thinking about taking the anchor off my boat and keeping it with me.
Thanks in advance. Roy |
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#3
02-02-2005, 08:31 AM
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Sounds like you are getting a hard pedal unless you rev the engine in neutral, and then it is okay? If the pedal is real hard sometimes, check the booster check valve.
if that engine configuration is making low vacuum you might need to go to manual brakes or add a vacuum pump. I dont know minimum vacuum required for the booster, but i would think at least 16-18"hg.
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#4
02-02-2005, 09:01 AM
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i'd say either the check valve is bad or the vac supply hose is sucking shut.
pull the hose and plug it and see if the engine runs differently to check for a bad booster but normally this doesn't come and go like you describe. i'd look at adding an aux vac pump and a vac reserve tank to that combo. the majority of 400's with the ra4 cam i've been around don't carry alot of low end vacuum. this can also cause the problem you describe. mike
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so many pontiacs, so little time.................. moderator is a glorified word for an unappreciated prick.................. "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." --Albert Einstein "There is no such thing as a good tax." "We contend that for a nation to tax itself into prosperity is like a man standing in a bucket and trying to lift himself up by the handle." - Winston Churchill |
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#5
02-02-2005, 04:58 PM
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Update,
It wound up that the distributor had worked its way loose and the timing was way off. Between a vacuum guage and a timing light I have it back on the money. Thank you all for the suggestions. I'm still thinking of the vacuum canister. Thanks again, Roy |
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