I picked up an early PU for my buddy bought, who lives in California. Its a sbc with a 700R4 trans. First thing I noticed when test driving it (and driving it home) was how hard the pedal was. Not getting any ***ist. (I have a booster in my 53 and have had other cars with boosters and this one is not working right. ) Upon getting home I decided to look into it to see if it was something simple. I notice the hose goes into the back of the intake (I have always put into the back of the Carb, which is a 1406 edelbrock) and I noticed something I have not seen, a canister (looks like a filter, see picture below)) in line. anyone know what it is for and is it needed. Also should the line be moved to the back of the carb instead of the intake. any suggestions. (yes it has those ****ty braided covers over the hose)
Pull the vacuum line off your booster and see if you have vacuum when the engine is running.. Next check the pedal ratio.. If I remember correctly the pedal ratio should be around 4 or 5 to 1 for power ***isted brakes. The other common problem is when installing a power booster the rod that actuates the master cylinder from the booster must be the correct length. Then you will be into checking for line pressure at each corner and each individual brake. Hope that helps......went through the same thing this summer on my model A. I don't think there is anything wrong with your vacuum source and I have never seen that little can thing before. It looks like a fuel filter.
I remember right that can is some kind of backfire protection valve, had a recall on my '76 olds to get one added, think I saw them on other GM cars too. Probably not really needed.
as stated above, check engine vacuum. 17" should be plenty. put a fresh piece of hose in there to eliminate that valve. it might be the proportioning valve may need to be reset. could be the booster is junk. any hissing sound? could be a restriction in the system somewhere like a collapsed line or hose. good luck and have fun.
I don't have a booster on my 55' stude, but I spent a lot of time picking the tech line's brains at SSBC. I learned that master cyl. bore diameter has a lot to with how brakes will behave and the how the pedal will feel. Followed their recommendations and my Stude stops like it has power brakes.
That is definitely a GM anti backfire valve. In the mid 70's-90's GM was installing them and also retro fitting them. They were supposed to keep gas fumes out of the booster, which would deteriorate the rubber in the booster. I don't think you really need it. KK
There's a fine line between moving enough fluid and bore size, another fine line between mc bore and wheel cylinder/caliper piston bore Then there's another between bore vs bore and pedal ratio. Think of those fine lines in the shape of a triangle that work together.
The vacuum source coming from the carb would be better, You need to make sure : the vacuum is getting to the booster The vacuum is staying in the booster The booster is responding to the vacuum by providing ***ist. Boosters go bad
You sound like the tech guy I talked to! It sure is nice to have brakes that you can depend on. (Knock on wood) wasn't trying to come across as knowing anything about brakes. Just putting it out there that those guys were a huge help to me.
more good info. I am going to swap out the line (remove the valve) to see what happens. the owner is coming up next weekend to drive it from Seattle to Sacramento. I will p*** along this info on ratios.
To see if the booster is working at all pump the pedal several times with the engine not running. You're using up any vacuum left in the booster. Put your foot firmly on the brake and start the engine, the pedal should sink towards the floor. If it does the booster is working and you probably have a pedal ratio or cylinder sizing problem.
I have driven my 4 whl disc brake(jag rear/speedway conversion early Ford) many miles and selected a 67 Corvette m/c with NO power ,no proportioning valve, and 6 to 1 pedal ratio using 39 Ford pedals and have superior brakes with not much pedal pressue(relatively easy to push) maybe I just lucked out,but I have excellent brakes with excellent pedal. Flatheadjohn47 Texas
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