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Discussion Starter · #1 ·
My brother-in-law has an "A" sedan streetrod. It has power brakes...yet the brakes are really stiff until the car has been driven then they work fine...this happens from a cold start or after the car has set for awhile. The line from the vacuum canister for the brakes is fed from the manifold, an Edlebrock Performer. He replaced the old dual master cylinder and booster. The engine is a freshly rebuilt 327 w/a mild cam, 350 auto...it runs great no issues there... vacuum is very good.
He is running a 1406 Edlebrock carb.

Now would it be feasible for him to put the vacuum line to the vacuum port on the back of the carb which can be used for power brakes on the 1406 and plug the manifold???? Would he notice a difference??? or is there something else causing this???...we did power air bleed the brakes, no air bubbles there.
you really have to stand on the brakes until the car is driven a mile or so.
sort of like losing the power brakes in a new vehicle.
 

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Trifive Automotive Electrical Wiring Expert
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It sounds like the pads/rotors are glazed or wet with fluid or grease and driving cleans them.
 

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Discussion Starter · #3 ·
No we pulled the frontpads and replaced them on the front discs(they were sort of glazed), cleaned the rotors(turned during the rebuild) w/ brake fluid...that was my first thought, then we pulled the rear drums, very clean no glazing on the brake pads or the drums...cleaned them also and still had the problem.
I'm no expert but it's like the brake vacuum canister doesn't get enough volume to activate the booster???yet again I'm no expert:):)

This car has about 200mi. on it and it has been this way since it was returned to the road according to Ed. Let it warm up, drive it for about amile then the brakes are good...stomp on them and the car stops instantly... yet gentle braking from first startup you do have to stand on them to stop...not fun!!
 

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I don't think you are going to gain any progress by moving your vacuum line from your manifold to your carb. What brand of pads are you using? How hard of material is the lining on the pad? Maybe once the pad gets warmer it softens up. :confused0006: just a thought.
 

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BAD BRAKES

I am wondering if you even have enough vacum to operate the brakes. Does the motor have a big camshaft. Try putting a vacum gage in the line . I think you need at least 15" of vacum to operate correctly. He may need to add a vacum cannister to the line.:anim_25:
 

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The other thing besides the glazed pads might be that they have a high metallic or ceramic content and they just need some heat in them to work well.

There are many other potential issues here, and the likelihood of problems might be a bit higher than with 55-57s but the issues are the same.

I'll list some.

1. Booster too small.
2. Master cylinder too big for the calipers.
3. Small bore calipers.
4. Pedal ratio.
5. Low vacuum from the engine.

The brake components need to work as a system. All the pieces need to match.

It might help if you could provide a list of components, as well as tell us what the engine vacuum is.

The vacuum port on the back of the carb is the same as the vacuum plumbed into the manifold.
 

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Discussion Starter · #7 · (Edited)
Ok, just got home from my brother-in-laws

Engine vacuum off the manifold is at 18-20 ", it flucuates when the car is first started then steadies out after it warms up a bit to a steady 19"
Cam is not radical just a mild performance one--Ed couldn't find the specs tonight
The car has a MII frontend using 11 " front discs, pretty much a "stock" type setup, pads we replaced were Napas for Ford discs, no competition or ceramic type pads
Calipers are typical MII/Ford type w/1 floating piston..everything is adjusted right
Booster is a dual brake 7" from Speedway
Wilwood dual 7/8" master cylinder
Rear drum brakes are Ford "stock", 9" rearend, and new
Manual proportioning valve from Speedway

and yes there is a vacuum cannister on the system

Checked the carb vacuum and it held steady from first start at 21"...Don't ask me but I always assumed manifold and carb vacuum would be the same:confused0006:
 

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Is there a check valve on the vacuum cannister (between it and the engine) to prevent it from loosing all it's stored energy (vacuum) after the engine is shut off...?
Or maybe the check valve is bad, it sounds like the vacuum is bleeding off when it sits a while...
With 18" to 20" vacuum you should be able to run straight from the manifold to the booster without an extra can...
 

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Discussion Starter · #9 ·
Dave, you may have hit on what it is. I do not think that there is a check valve on the canister...I'll have Ed look it over this evening after he gets home from work. I never thought to check if there was a check valve...Ed installed the same basic brake system I used in my '33 Vicky and I know I had a check valve in the line....maybe the lack of one is the culprit???

Thanks for the heads up!
 

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check valve

You may want to see that there is good strong vacuum making it to the booster, then ensure the check valve works if one is actually present. Do you hear hissing inside the passinger compartment ? mabe a vacuum leak into the inside of the car. ensure there is no carbon build-up where the vacuum fitting connects to the engine as it may reduce the volume of vacuum produced by the engine.
hope this helps
regards
Dave
Dave, you may have hit on what it is. I do not think that there is a check valve on the canister...I'll have Ed look it over this evening after he gets home from work. I never thought to check if there was a check valve...Ed installed the same basic brake system I used in my '33 Vicky and I know I had a check valve in the line....maybe the lack of one is the culprit???

Thanks for the heads up!
 

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There is a good troubleshooting procedure for power brake boosters at mpbrakes.com. Check it out. Covers the check valve, air valve, etc.

From the list, there's nothing wrong! So if the checks for the vacuum deal check out, everything else is still suspect, so go back through it.

Did the brakes on this car ever work as expected? Or has this been a problem since the build?
 

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Discussion Starter · #12 ·
RickL, this car was originally built in the late 70'-early80's, was sold a couple of times and the last owner started a rebuild until he was forced to sell it. Eddie bought it last year and has since rebuilt the engine, replaced the trans with a 350th, it originally had '48 Ford drums front and rear is a narrowed 9'' Ford with manual brakes, Ed has since converted to discs on the front, installed a new Wilwood dual master with a Speedway 7" dual booster. When the car has been driven say a mile or two then the brakes work great otherwise you really need to stand on them worse actually than when it had the non-power drums all around and no booster. And after the car sat for awhile, say an hour or two after being driven then restarted the same thing would occur again.

Anyway an update: we worked on the A's brakes yesterday. There was no check valve between the vacuum canister on the manifold vacuum line. So we installed one and that helped a lot yet was still not great the car still needed to be driven for a bit before the brakes started working right. So we then removed the vacuum line from the manifold and installed it on the vacuum fitting on the back of the EDlebrock carb and plugged the intake manifold just to see if it made a difference....now the brakes work great all the time, from first start, and even after sitting for a couple of hours. Seems the addition of the check valve and moving the vacuum line solved the problem. The car is now fun to drive and best of all it now stops easily right away. We had previously gone thru the brake system, replacing the front pads, made sure there was no air in the lines, cleaned the front rotors and the rear drums and pads.

Anyway thanks to all that offered their advice and counsel:)

P.S. Any advice on how Ed can get his wife not to hand him his head on a platter after he tells her he is having the interior done next week? For you see his deal with her is he would not spend a lot right away to fix the car up but would spread it out over time. So in about a year he has rebuilt the engine, new trans and fittings, new fuel tank,lines and fittings, new brakes, master cylinder/booster and lines/fittings, new paint/bodywork just a couple months ago, new rims and tires, new SW vintage gauges, new Lokar shifter and fuel feed and the list goes on...he said there for awhile UPS or FedEx was delivering boxes to his office nearly everyday and he'd sneak stuff home:sign0020:
So now she has wised up and sort of laid down the law so to speak...she and her sister, my wife, are sort of the same in that regard, what they don't know won't hurt us, until they find out:)...he asked me what I'd do I just told him good luck and asked him if his car was comfortable to sleep in:sign0020:
 

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simple solution

This is easy the car gets new interior for him the house gets new interior for her !!!!
RickL, this car was originally built in the late 70'-early80's, was sold a couple of times and the last owner started a rebuild until he was forced to sell it. Eddie bought it last year and has since rebuilt the engine, replaced the trans with a 350th, it originally had '48 Ford drums front and rear is a narrowed 9'' Ford with manual brakes, Ed has since converted to discs on the front, installed a new Wilwood dual master with a Speedway 7" dual booster. When the car has been driven say a mile or two then the brakes work great otherwise you really need to stand on them worse actually than when it had the non-power drums all around and no booster. And after the car sat for awhile, say an hour or two after being driven then restarted the same thing would occur again.

Anyway an update: we worked on the A's brakes yesterday. There was no check valve between the vacuum canister on the manifold vacuum line. So we installed one and that helped a lot yet was still not great the car still needed to be driven for a bit before the brakes started working right. So we then removed the vacuum line from the manifold and installed it on the vacuum fitting on the back of the EDlebrock carb and plugged the intake manifold just to see if it made a difference....now the brakes work great all the time, from first start, and even after sitting for a couple of hours. Seems the addition of the check valve and moving the vacuum line solved the problem. The car is now fun to drive and best of all it now stops easily right away. We had previously gone thru the brake system, replacing the front pads, made sure there was no air in the lines, cleaned the front rotors and the rear drums and pads.

Anyway thanks to all that offered their advice and counsel:)

P.S. Any advice on how Ed can get his wife not to hand him his head on a platter after he tells her he is having the interior done next week? For you see his deal with her is he would not spend a lot right away to fix the car up but would spread it out over time. So in about a year he has rebuilt the engine, new trans and fittings, new fuel tank,lines and fittings, new brakes, master cylinder/booster and lines/fittings, new paint/bodywork just a couple months ago, new rims and tires, new SW vintage gauges, new Lokar shifter and fuel feed and the list goes on...he said there for awhile UPS or FedEx was delivering boxes to his office nearly everyday and he'd sneak stuff home:sign0020:
So now she has wised up and sort of laid down the law so to speak...she and her sister, my wife, are sort of the same in that regard, what they don't know won't hurt us, until they find out:)...he asked me what I'd do I just told him good luck and asked him if his car was comfortable to sleep in:sign0020:
 
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