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Do you recommend this?

Dreadl0ck

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https://www.performanceonline.com/1...er-brake-booster-kit-wilwood-master-cylinder/

Background, my 69 roadrunner was converted to 4 disc brakes from SSBC with a weird looking setup:



Can't get it to work properly (pedal goes soft without warning even though I replaced fluid and bled the brakes 10 times) plus it's poorly adjusted so I figured I'd just replace the whole thing.

The kit I posted at the top - do you recommend that or something else? Thanks
 
If the pedal is soft you probably have air in the lines, not enough vacuum ( what kind of cam are you running?), or an improperly adjusted pushed.
SSBC makes a good product, I would try to get it working by doing a little tshooting first...
It's hard to tell in your pic but where is the booster getting it's vacuum? Should be off of the bottom of the carb or better yet off of the manifold.
 
I've tried bleeding it numerous times so I believe it's something bad with the master cylinder.

Vacuum is from electric vacuum pump located under the battery. Wouldn't no vacuum give rock hard brakes (like manual brakes?)

Brakes are probably fine - it's the booster and main cylinder package I'm worried about and thinking about replacing.
 
Pressure bleeding or gravity bleeding. Not sure what your system requires but it makes a difference.
 
I have a car that needed more vacuum for the brakes so I added an electric pump too. It is plumbed in to the booster along with the engine vacuum. Works great. Not sure that just an electric pump would be enough, is there an additional vacuum tank? You must have a big cam with lots of valve over lap to really need additional vacuum. I would hook it up to the engine and then the pump before you spend big money.
 
But would it really be soft brakes if vacuum isn't enough? Brakes feels spongy and not distinct at all when they do work, and then all of a sudden just nothing.

When you say hook it to the engine, and then to the pump - can you describe that a little closer how you mean?
 
As mentioned above there is a port in the intake manifold just under the back of the carb. It should have a plug in it, remove the plug, install a fitting in it place that allows you to run a vacuum hose from the fitting to the booster. Then you will have engine vacuum which should be enough. If it is not then "T" into the vacuum hose with the line off of the electric vacuum pump. Make sure you have no vacuum leaks.
 
I hope that I am not insulting anyone with the following....
Engines with rowdy camshafts often deliver very low idle vacuum. The long duration and heavy overlap makes for great power increases at midrange and high rpm but it also diminishes the low speed performance and idle quality.
I had a big cam in my 440/493 and the power brakes were way too stiff. The idle vacuum was around 5 lbs in gear! I added a vacuum can but it was not enough. A vacuum pump was added and it worked great. Later, I switched to a smaller cam and the idle vacuum was around 12 lbs. That was enough to work so I removed the pump.
Another option is to run a simpler manual brake setup...No issue with vacuum to deal with with a manual setup.
 
Have you replaced any of the brakes lines? IIRC if they are not tight enough they will let air in with no loss of fluid.
 
I agree Kerndog, one other thought was I have seen old soft rubber hoses expand and blow up like a balloon before eventually leaking when you step on the brake. Therefore the pressure never reaches the brakes.
 
Was thinking , just check the location of your bleeders, there is one aftermarket brand and I can't remember which that had the bladders a little lower than straight up 12 o'clock. I think they even recomended bleeding them with the calipers off so you could orient the bleeder up...
I've had boosters cause /have different symptoms, I wouldn't call it a soft pedal but soft stoping...to me they are definitely a pita to t shoot but if they don't have vacuum or the check or diaphragm is bad braking will suck.
Hash brings up a great point ,if those rubber lines are old they will expand and not force the pressure into the caliper..
 
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Was thinking , just check the location of your bladders, there is one aftermarket brand and I can't remember which that had the bladders a little lower than straight up 12 o'clock.

?????
 
Alright, let me see here if I can answer all questions. Brake install was by previous owner, hence I'm looking at replacing the booster+main cylinder to know that everything is correct.

Yes, it has quite some overlap and long duration camshaft, it only measures about 5 lbs vacuum, why I installed the vacuum pump. I've had a hard time finding a good tight check-valve but with bad connection there - there wouldn't be any brake boosting going on - and that's not the case here - spongy slow stopping with occasional total failure.

I'm running Motul dot 4 RBF660 fluids - I had some idea that the reservoir was too close to the headers causing the fluid to boil - so I went for a high temperature fluid.

Brake lines are brand new - no leakage there

With pressure bleeding, the orientation of the bladder wouldn't be an issue and I've checked with with SSBS and they said "normal" bleeding would be enough.

Again, since I didn't build it - I want to eliminate all sources of errors and do it properly.
 
I would replace the master cylinder first before spending on a new setup. Occasional no brakes is a master cylinder issue.
 
Problem is that the booster is a bit dodgy with poor fitment, so I figured I'd might as well get it as a package. Would 9" fit or should I go for the 8" ?
 
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