Author Topic: 11" brake booster for my 6.4 swap - need help (Read 4551 times)

daryld · « **on:** July 22, 2018 - 02:46:05 AM »

Guys,

So I am nearing the end of my pro touring 70 Cuda build with a 6.4 392 and have run into issues with my brakes. I had a 9" booster with a OEM style master when I had my 440. I recently changed the master to a Wilwood 1" bore and kept the 9" booster. Now my breaks won't stop the car for nothing even though the pedal is hard as a rock. I am pretty sure I have narrowed the problem down to two things. The 9" booster is not big enough for the vacuum pressure from the 6.4. I may also need a smaller bore in my Wilwood MS.

From the research I have done it appears that people who have done these swaps and wanted to keep power brakes had to either use an 11" booster or hydroboost. Can someone please tell me where I can get an 11" vacuum booster for my Cuda? I really don't want to have to re-run my hydraulic hose in order to run a hydroboost. I am almost tempted to just take the booster off and run the MS strait to the firewall. Would save me a lot of headache and more money.

While I have your attention, I am also having a lot of whining from the factory power steering pump. I have had to add pressure reducer and run a cooler. Seems as if these pumps have way to much pressure for my rack and make the fluid very hot. I have had to dial the pressure way down to get the wining to tapper off but I still hear it under hard turns and now it is like not have power steering. If any of you have dealt with this issue please let me know what you did to resolve it.

I just want to enjoy driving my car and I want it to stop. Any help you guys can lend me would be greatly appreciated.

Thanks
Daryl

70chall440 · « **Reply #1 on:** July 22, 2018 - 11:33:50 AM »

Daryl - I would dump the booster and run a straight MC. I researched this pretty extensively when building my Cuda and arrived at the conclusion I didn't need it to stop the car. I believe I used a 3/4" bore Mopar MC. I have to admit that the car is not yet running/driving so I cannot state that it works conclusively, however a friend of mine was running the exact same set up on his road race car (which is where I got the idea). I drove that car in some auto X and the brakes were great; very firm and responsive.

As to the PS pump, could be a bad pump as it should not be having those issues with a R&P system. Stock pumps on new vehicles do have very high pressure (1200-1400 psi) but most R&P systems are designed to take it, unless what you have was designed for the stock old school pumps (about 800 psi max).

rusty dodge · « **Reply #2 on:** July 24, 2018 - 02:11:31 PM »

A 79 aspen 11" single one fits. Not sure if it would clear the valve cover in your combo but it fits firewall. I'm installing one right now actually, in my 74 chally with a 440 in it and MP cast valve covers. About 1/4" room between booster and valve cover. This booster takes new style 2 bolt master so get that too. about $90 bucks on Rock auto for both.

I orig. had the stock 10 inch single booster and 4 bolt master. Wanted to try manual. Swapped it over with 15/16 aluminum master and the straight adjustable pedal rod. Drove around the block and decided -- hell no that's not going to work. Took that stuff off and gong back to power brakes.

Almost pulled the trigger on the hydroboost setup but then figured I would give a new booster a shot.

I see many people say manual disk brakes are ok, but I don't see how you can get the line pressure required for disk brakes. Drum brakes sure, only need 300psi. Disk brakes need 1500 psi or more from what I have read. I don't see how you could get that kind of pressure without a booster.

70chall440 · « **Reply #3 on:** July 24, 2018 - 03:06:47 PM »

Manual discs have and are used by many platforms. I can't speak to the actual pressures but I do know that non boosted master cylinder with the correct bore diameter will provide the necessary braking force.

GoodysGotaCuda · « **Reply #4 on:** July 24, 2018 - 04:30:36 PM »

I�ve more than pegged my wilwood caliper pressure gauge when using a manual master cylinder. The gauge stops at 1,500, I think I hit around 2,500psi.

1� bore with a booster should be no problem.

I haven�t read the entire thread, but bleeding my wilwoods was an extensive process and took a few weeks worth of driving to really get it all out.

For what it�s worth, I would like to install a booster. My pedal effort is okay, but the stroke is too long. I would like a shorter stroke with the same [or less] effort....which means a booster.

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70chall440 · « **Reply #5 on:** July 25, 2018 - 11:12:24 AM »

Goody - what MC are you using?

GoodysGotaCuda · « **Reply #6 on:** July 25, 2018 - 11:38:18 AM »

Quote from: 70chall440 on July 25, 2018 - 11:12:24 AM

Goody - what MC are you using?

7/8� wilwood

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70chall440 · « **Reply #7 on:** July 25, 2018 - 11:43:26 AM »

I believe I am running a 3/4" Mopar MC, I had to search pretty hard for it as I remember. I will have to go back through my notes, I believe the MC I am using was not very common or isn't now; seems it was a manual disc, rear drum MC. A buddy was running one on his Lemons car which is where I got the idea.

GoodysGotaCuda · « **Reply #8 on:** July 25, 2018 - 12:14:39 PM »

Quote from: 70chall440 on July 25, 2018 - 11:43:26 AM

I believe I am running a 3/4" Mopar MC, I had to search pretty hard for it as I remember. I will have to go back through my notes, I believe the MC I am using was not very common or isn't now; seems it was a manual disc, rear drum MC. A buddy was running one on his Lemons car which is where I got the idea.

Id imagine it has quite a bit of stroke as well. I love the pedal feel of manual brakes but the stroke length can be a little concerning for a quick decision on city streets. No problem for racing.

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70chall440 · « **Reply #9 on:** July 25, 2018 - 02:24:04 PM »

I will let you know, I am having some wiring issues at the moment.

PlumCrazyChris · « **Reply #10 on:** October 03, 2018 - 02:29:09 PM »

I have the old 76 Dart manual disk brake MS on my Challenger. It works fine, but as Goody mentioned, the pedal stroke and effort is more than I like. Has anyone used the "hemi" booster for their cars? Its smaller diameter and sort of sticks out away from the firewall a few inches. I have installed thru-wall battery connections on the firewall under the MS and don't think a standard MS will fit.

I think one of those would fit, but would love to see a pic of one installed and see if it works alright.

Chris

70chall440 · « **Reply #11 on:** October 03, 2018 - 03:50:10 PM »

Quote from: 70chall440 on July 25, 2018 - 02:24:04 PM

I will let you know, I am having some wiring issues at the moment.

I have finally attended to the brakes to a degree, they still need another bleeding. As to the stroke, it is a bit long but to be honest I cannot tell if it is too much bc I dont have seats in the car so its hard to say.

Kevin71 · « **Reply #12 on:** September 20, 2019 - 05:12:12 PM »

What did you do about the power steering? Can you get a different pump? I have seen where people talk about a pressure regulator on it. I am considered going this route. looking a 6.4 hemi. It appears that with all the parts it's about 15k not counting any labor.

daryld · « **Reply #13 on:** October 03, 2019 - 12:20:20 PM »

Sorry, this is an old thread and I do not get on here much. I actually winded up going with a hydoboost set up with Wilwood 1 1/8 bore MS. I could not get my 8" booster to work and did not have the room for an 11" but wanted to keep power brakes. I also was not sure the 11" would give me enough pressure. Not only would the brakes not work but the stock PS pump was too much pressure for my rack. I even installed a pressure reducer and cooler and it was still whining. Going with the hyrdrboost was the best $900 bucks I could have spent. The brakes work awesome. I did have to put a washer or two between the booster and MS because the shaft is not adjustable and it was causing the brakes to always grab. A very cheap and simple fix.

I also had to switch to a GM PS pump. You can get a lower PSI stock pump from Bouchillon but I wanted a nice reservoir and Magnumforce had the complete set up along with the pulley and bracket to make it all work.

Hope this helps.

Kevin71 · « **Reply #14 on:** October 07, 2019 - 10:15:50 PM »

I have decided to go with a more stock setup. It's complicated enough for me anyway.
Thanks

Author Topic: 11" brake booster for my 6.4 swap - need help (Read 4551 times)

daryld

11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

rusty dodge

Re: 11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

GoodysGotaCuda

11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

GoodysGotaCuda

Re: 11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

GoodysGotaCuda

Re: 11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

PlumCrazyChris

Re: 11" brake booster for my 6.4 swap - need help

70chall440

Re: 11" brake booster for my 6.4 swap - need help

Kevin71

Re: 11" brake booster for my 6.4 swap - need help

daryld

Re: 11" brake booster for my 6.4 swap - need help

Kevin71

Re: 11" brake booster for my 6.4 swap - need help