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Old 05-01-2003, 01:38 PM
stanjr41's Avatar
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Post power brake booster

Hi; I'm a new guy who needs a miracle; or just some good help.I have a 1941 chevy sedan with a mustang front suspension, chevy 11" front discs,1977 camaro rear with drum brakes,1977 camaro master cylinder and proportioning valve ,and an original 1979 pinto power booster.The drivetrain is 350/350 chevy.I have been driving the car for 5 years with no problem. The boosters diaphram ruptured,so I bought a street rod 7" booster to replace it.Easy,right?now it takes two feet to stop from speed.Motor has 19"of vacuum, the pedal is adjusted right,check valve is working,none of the high pressure side was touched.The supplier is lost for suggestions;how about you guys?really need help so i can drive it.

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Old 05-02-2003, 06:31 PM
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I'm trying to figure out if your brakes are locking or you have poor brakes since you say it only take you 2 feet to stop from speed? If your saying you have poor braking then I'll go from there. I see you mainly replaced the booster and went down in size. I take it you adjusted the rod inside the booster to the back of the master cylinder so it was just slightly away from the piston when the master cylinder was bolted up to the booster. I'll wait for a reply before I go further because I don't want to be making the wrong assumptions.
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Old 05-03-2003, 12:52 PM
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Thanks for helping. What I meant was I have to use both feet to stop the car from speed; which is around 25 mph. I am afraid to go any faster.I have the rod between the m/c and booster just barely away. The pedal rod has about 1/2"of movement before I can feel the braking start to begin.I removed the m/c and depressed the pedal and there is 1 1/4" of movement in the rod that goes to the m/c. I fastened the m/c back down and depressed the pedal and the rod going into the booster moves 5/8".I'm sure the m/c has more than 5/8" travel.I measured the bore size of the m/c at the end and it is 1 1/8".I also added a thin rubber gasket between the m/c and the booster to make sure it was sealed. I read that a leak there could cause a hard pedal. I hope the additional info. helps. Thanks
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Old 05-03-2003, 02:16 PM
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You might try a 1" bore master cylinder. The theory is the bigger the bore the less pressure you will get out of the master. So with a 7/8 or a 1 inch bore master, you will get more pressure to the brake cylinders. Other wise maybe a larger booster will take care of it....GlennK
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Old 05-03-2003, 08:33 PM
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I think your only solution is to go with at minimum is a dual diaphram 8" booster.

You know their are two holes on the pedal arm where the rod from the booster to the arm attaches...(upper for non-power brakes and the lower for power brakes). Try moving the arm to the upper hole for more leverage and see if your braking improves.

Joe
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Old 05-06-2003, 06:24 AM
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Thanks for the sugestions. I am using the original 41 chev. floor pedal,so there is no other hole. I figured out the pedal ratio and it is 3.5 to 1. If I drill another hole 1" higher it is 5.25 to 1. I don't want to weaken the pedal,so if several people think this will help I will try it. I' m not working, so buying another booster is not an option unless someone wants a good deal on a brand new 7" booster.I measured the pinto booster and it is 7.50" at its widest spot;so I figured it was a 7" also. That's what I get for thinking.
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Old 05-06-2003, 07:16 AM
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It is a bummer how thinking can get to you! I'm dying to know why you chose a rodshop product when the stock Pinto booster was working fine for 5 years worth of driving. I follow the simple rule...if it works don't f**k with it!
But I've been where you are too, so I am very sympathetic.
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Old 05-06-2003, 07:48 PM
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yeah, when you get old the memory don't do what it should. The original pinto booster had a basically flat rod that curved upward with an eyelet to connect to the pedal. I had to do some major modifying to end up with a straight threaded end so that I could couple the pedal rod to it.It seemed easier at the time to get a booster designed for rods and be done with it. Anyway, I talked to the dealer today that I got it from and he agreed to take the booster back as defective and refund my money. He didn't want to sell me a larger booster though-said he didn't want to be stuck with 2 boosters he couldn't sell. I don't blame him. Anyway, I bought an 8" dual diaphragm from Southern Air and it should be here in 5 days. We'll see what happens then. Thanks to all of you for taking the time to try and solve my problem
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Old 05-07-2003, 01:36 PM
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Let us know what happens when you install the new booster.
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Old 05-07-2003, 01:54 PM
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You have Jensen auto salvage yard up there in Fresno. Used to be a world class yard and when I drive by it in 99 it still looks impressive. I used to live there when I was going to FSC. Why not get one there?
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Old 05-08-2003, 07:31 AM
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Thanks for the replies I'll be sure and post an update when I get the new booster.Willys36-The Jensen wrecking yard is now one of those Pull-N-Save self help places. I did the original booster about 5 or 6 years ago.I don't have the capabilities now that I had then.Besides, I've got the 8" on the way.It may take me forever but I'm one of those people who wants to do everything himself no matter what(ego I guess).
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Old 10-16-2005, 11:17 PM
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re: power brake booster

How did you fix your problem? I have a similar problem and I'm curious what the solution was.
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Old 10-18-2005, 12:27 PM
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I guess the real question is why didn't you just order a replacement Pinto booster, but I think the 8" dual diaphragm will fix you up. Now I wonder if the Pinto booster was dual diaphragm, or you just got lucky that the pedal ratio on the 41 Chevy was about the same as a Pinto!
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