Hard Pedal

[Gospel Runner]

I did not get a chance to check the vacuum pressure. I thought I could use my cylinder leak gauge, but it did not work. I bought one this afternoon and I will check it tomorrow. I do have a bunch of pics that I hope will help.

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[Car Nut]

You've got this "bass assward", smaller bore for manual, larger for power.

That's what I get for posting late.

 

[Gospel Runner]

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[Gospel Runner]

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[Gospel Runner]

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[Sixpactogo]

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Gospel Runner,
Looking at your booster, it appears you have the single ballast booster that came with drum brakes. It may not be all of your problem but IMO you need to upgrade to the dual ballast unit. Here is a pic from ebay. I made the same mistake when I put the front discs on my Charger

 

[Gospel Runner]

The pump is putting out 18 inches of vacuum. My booster is not connected to my engine so starting it with my foot on the brake to see if the booster is bad, will not work. Is there another test I can perform to see if the booster is working at all?

 

[Gospel Runner]

Today I called SSBC to see if they could direct me in what I should do next, and they were useless. I will have to make a decision whether to bite the bullet and change my single ballast booster to a duel or wait for my tranny to come back and keep trying to bleed and play with the set up I have. I am leaning towards getting the duel ballast unit while the car is down.

 

[Billccm]

Send an email to Dr Diff. If he advises a dual booster then you can get one from him.

 

[JG1966]

Do you have the electric vacuum pump connected to intake manifold vacuum? Maybe try running your hoses using option 2 on vacuum pump instructions. I had same setup and same problems. Turns out the my vacuum canister was bad. (I was getting 18 inches out of vacuum pump to canister but only 15 inches from canister to booster). I removed vacuum canister and ran left hose on electric vacuum pump to engine vacuum and right hose to brake booster -- and removed canister-- and it's much better.

 

[Gospel Runner]

I just sent an email to Dr. Diff.

I have no means by which to connect this system to my engine as this carb has no vacuum tube. I would have to add a plate, but that seems counter productive since there is no usable vacuum from the engine. High lift cam at .691.

 

[Gospel Runner]

Dr. Diff said I need a smaller bore MC maybe 7/8" and a dual diaphragm booster that costs $300. I just shelled out $150 for the power booster and $280 for the MC. I have to see if I can return these items before I can afford the new ones. Anyone need a single diaphragm booster or a 1-1/32" bore MC?

 

[Sixpactogo]

Dr. Diff said I need a smaller bore MC maybe 7/8" and a dual diaphragm booster that costs $300. I just shelled out $150 for the power booster and $280 for the MC. I have to see if I can return these items before I can afford the new ones. Anyone need a single diaphragm booster or a 1-1/32" bore MC?

I had the same issue as you. I also spent a couple hundred dollars to rebuild the single ballast booster before finding out it wouldn't work with the front discs. Mine is collecting dust as well. The picture I put on here in post 26 is for sale on Ebay for $199.00 with free shipping. It is the one that I bought and works fine for me. If Cass at Dr Diff says you need a 7/8" master, it must be because of your lack of vacuum. Anyway, just a heads up on the booster install. The dual ballast unit has a larger diameter rubber boot than your single one does so you will have to enlarge the hole in your firewall to get it to fit.

 

[Billccm]

I know it's a lot of water under the bridge now, but have you considered a Dr Diff manual 15/16 master cylinder? Many people on this forum are running this set up (including myself).

 

[lewtot184]

a big cam needs an aggressive ignition curve which will help vacuum. factory boosters seem to be marginal at around 14". may not be want you want to hear but i'd ditch the cam. probably a big hydraulic.

 

[Gospel Runner]

Sixpactogo what is the part number for that booster?

 

[Gospel Runner]

I do not have the money to try all of these remedies. I am going to save up and get this dual ballast booster. If it works I will be satisfied.

 

[Gospel Runner]

Does ebay sell the booster without the MC?

 

[Billccm]

I do realize your frustration and I've been there where lots of money has been spent and still no resolution. Having said all that, I'd buy from Dr Diff. He stands behind his products. I had a nightmare of a time with my Dr Diff disc conversion. After removal of the master cylinder for the forth time to bench bleed I stripped out the threads. I emailed Dr Diff and asked him to sell me another master cylinder as it was my fault. Dr Diff sent one on a Saturday morning and charged me NOTHING. I offered to pay shipping, and he said it was on him.

Once you buy from Dr Diff you will get support until the issues are resolved!

 

[Sixpactogo]

Does ebay sell the booster without the MC?

I bought mine from Pirate Jack. They sell just the booster. Here is a link to their Ebay auction.
1966-70 Mopar OE Bendix Style 8" Dual Power Brake Booster for Mopar B Bodies |
The factory pn for 68-70 is 2883 056. You won't find one but you asked. As far as I know all of them available these days are built in China but are as close to factory specs as what is out there.