4 wheel power disc brakes that still aren't enough. PROBLEM SOLVED !!

[Kern Dog]

I really need to improve the brakes in this car!
I'm running the Cordoba 12" front rotors with single piston 2.75" sliding calipers. The rear is the Dr Diff disc kit with 10.7" Toyota based rotors, 1.5" single piston Mustang based calipers. I have a 75 Dart power booster with a 15/16" master cylinder. The engine makes low idle vacuum so I added a vacuum storage tank, but it still isn't enough. High speed braking is great but at lower speeds, the brakes just are not nearly good enough. I have looked at using an electric vacuum pump but the new kits are often $260 and up.
In 2012 I tried switching to a non power (manual) master cylinder. I tried 4 different ones, all with different bore sizes ranging from 15/16" to 1 1/8". None of them worked well either. Each one was capable of developing a firm pedal but none of them gave adequate braking. In fact, the braking was so bad, I was barely able to get the tires to skid on gravel! I really like the light weight and simplicity of a manual brake system and would prefer to go that route but with the luck I had, I really would benefit from seeing what other setups that other guys have used.

[fy469rtse]

Got similar problems, had some improvements going up to 13 " rotors and twin piston calipers,15 " inch rims  what power booster you got ,
I switched to hemi style diafram , marginal improvement, considering reservoir and pump like you, but starting to think more and more about the hydro boost set some guys on here have used, all the above adds up to over half of what it costs and the results are worth it ,
Like you stroker big block 505 with poor vacuum

[Finn]

Did you try adjusting the rod between the master cylinder and the booster?

[myk]

If low engine vacuum is a problem then the hydroboost setup is the only solution I can think of...

[Kern Dog]

Did you try adjusting the rod between the master cylinder and the booster?

No, I haven't tried that.

The pedal gets firm and is not anywhere near the floor. The brakes worked better with the 509 cam because it had a bit better idle vacuum than this Lunati I have now. I can pop it into neutral & rev the throttle and the brakes work much better.
I haven't looked into a Hydraboost system. It involves changing the P/S pump and  mine is fairly new.

[WHITE AND RED 69]

Hydroboost is the way to go. Never heard any complaints (other than the cost) from anyone who has used one.

My old brakes were the same, would barely have enough pressure to lock them up. Tried installing a vacuum reservoir, no change. Didn't want to listen to an electric pump running all the time so I installed a hydroboost setup and it made it like a new car.

You don't need to change the steering pump or box. The unit plumbs into the existing system with new lines included in the kit.   

[1974dodgecharger]

I'm shocked i heard the 509 is so low in vacuum it could not operate anything so people go to lunatic.

Did you try adjusting the rod between the master cylinder and the booster?

No, I haven't tried that.

The pedal gets firm and is not anywhere near the floor. The brakes worked better with the 509 cam because it had a bit better idle vacuum than this Lunati I have now. I can pop it into neutral & rev the throttle and the brakes work much better.
I haven't looked into a Hydraboost system. It involves changing the P/S pump and  mine is fairly new.

[Cooter]

One simply cannot mix and match brake parts such as HUGE calipers and a master cylinder that isn't matched.
My own junk has complete disc brake set up from Dart. Works awesome as a matched set.

[Kern Dog]

Guess you didn't notice that I mentioned that it is a "vacuum" issue, not a mismatch of brake components. The braking is excellent when the vacuum is above 12" or so.

[NMike]

well if $260 is too much for you to fix the vacuum issue, then the other solutions will be more offensive to your wallet

[Cooter]

Guess you didn't notice that I mentioned that it is a "vacuum" issue, not a mismatch of brake components. The braking is excellent when the vacuum is above 12" or so.

Not when you are going to manual which is what you stated as well. Good boosters (vacuum) can cover up a mis-matched combo, and force it to work ok.

[Dino]

Easiest and probably cheapest in the long run is getting a hydroboost setup.  Maybe you can get one from a junkyard truck or something to keep cost down a bit.

[Cooter]

Cheapest would be a vacuum reservior.

[Dino]

Cheapest would be a vacuum reservior.

Yeah that's true.  That would be cheaper than even a junk yard hydro unit.

[Kern Dog]

Cheapest would be a vacuum reservior.

I have one mounted behind the LH headlights in the wheelwell. It worked okay with the 509 cam but not so much now.

[472 R/T SE]

Vacuum pump solved all those issues for me.  They vary in price drastically.  I got a cheaper one & it's been fine since.  That was 8 years ago.  I don't mind the sound, I just tell folks' it's a fuel pump or turn the stereo up & say "huh" when they ask what the sound is.

It's a pretty important part for me.  If the motor dies on me I still have the pump delivering vacuum for brakes & that's kinda vital for me since I don't use hand controls in my Charger.

Here's one for $149.

http://www.summitracing.com/parts/hla-009428087/overview/



Heck, here's one for $50.  It's model specific but your Charger won't know the difference.
http://www.summitracing.com/parts/rnb-904-214/overview/



http://www.summitracing.com/search/part-type/vacuum-pumps-street?PageSize=100&SortBy=Default&SortOrder=Ascending&tw=vacuum%20&sw=Vacuum%20Pumps%2C%20Street

[Mike DC]

Are junkyard hydros a realistic option? 

The idea of saving a few hundred bucks is nice, but the idea of using an OEM item that will still be available 15 years from now is even nicer. 

[elacruze]

Sounds like you have crap brake pads. I use these and love them- http://porterfield-brakes.com/images/portstrt2008_11_06_02_45_30.pdf

Where did you get your rotors? I bought Cryo-treated drilled and zinc-plated rotors here; http://www.frozenrotors.com/

I use Dr. Diff's manual master cylinder kit with heat shield and stock drum rears, and I can smoke 'em any time I want to. They are smooth, powerful, and I never wonder if I need power brakes.

[Kern Dog]

Sounds like you have crap brake pads. 

I appreciate the response, but the problem is not with the brake pads. The car stops perfectly fine with the engine revving in neutral. It is at that point that the engine is making 15" or more vacuum.

[Kern Dog]

Today a friend from our local Mopar club gave me a vacuum pump that was originally from a late 80s Cadillac. I bolted it in the LF wheelwell behind the headlights. It is wired to be ON when the ignition is on. It makes some noise but once the engine is running, the cam and exhaust drowns it out! 

I'll drive it tomorrow but even just driving back and forth a few feet in the shop I can feel that the brakes are MUCH better.