Replacing MC on a 66 with a dual bowl

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wallyblackburn
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Re: Replacing MC on a 66 with a dual bowl

Post by wallyblackburn » Wed Dec 04, 2019 6:10 pm

wallyblackburn wrote:
Wed Dec 04, 2019 3:56 pm
Just for grins, I hooked a vacuum pump up to my power brake booster...

Even pumping furiously, the needle never even moved :( - this thing is obviously shot. I've never really done much with these - can they be DIY rebuilt? I see O'Reilly has a rebuilt one for just shy of $150...wow! Saw some of the other threads talking about a universal one - anybody have any luck there? I'm thinking of just sticking with the stock unit now that I've got the dual MC worked out.

Looks like mine is the Bendix twist-lock unit.

Appreciate any advice,
Wally
Just talked to a super nice lady at Power Brake Exchange in California. For $106.75 they will rebuild my unit. They don't have any in stock, so I'd have to send it and wait. She said it take 2-3 days for them to turn it around.

http://www.pwrbrake.com/inventory/386-u ... cyl%2F8%2F

I found this by looking at Rockauto and searching for what they had listed on Google...

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RedBird64
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Re: Replacing MC on a 66 with a dual bowl

Post by RedBird64 » Wed Dec 04, 2019 6:55 pm

That's a good deal, especially if yours is pretty nice ie not rusted, pitted and dented. When I called Booster Dewey about mine, he said most of them he gets as cores are beat and have had MC leak into them. Mine was cosmetically great so I sent it in for rebuild.

Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

wallyblackburn
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Re: Replacing MC on a 66 with a dual bowl

Post by wallyblackburn » Thu Dec 05, 2019 9:54 am

Just for fun, I called NAPA (they list one online - call for availability). Guy said there are none available, which means they are waiting for cores to rebuild. This picture just got real clear!

Wonder how difficult it would be to make something like this work:

https://swperformanceparts.com/1964-65- ... r0QAvD_BwE

I'm more than a bit confused...

Wally

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RedBird64
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Re: Replacing MC on a 66 with a dual bowl

Post by RedBird64 » Thu Dec 05, 2019 12:12 pm

Wally, that booster is only a single 7" where as the unit on 64's are 9" and the 65~67 are double 9's (20% more assist than a single 9).
So the Mustang unit would not provide nearly as much assist.

The whole thign is ultra confusing! Everything in the system affects everything else!
Looking at the changes that both Ford and GM made during the early years of disc brakes, it looks as though even they were learning and tweaking stuff.

Scott
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

wallyblackburn
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Re: Replacing MC on a 66 with a dual bowl

Post by wallyblackburn » Thu Dec 05, 2019 5:00 pm

Yeah, and I feel like I'm bouncing around like a fart in a windstorm, but now I'm thinking of picking up where Dave G. left off with the Universal unit from Inline Tube. This is, of course, after I've already modded my hood brace.

Their unit is made to work with a GM master cylinder. Lord only knows how that will fit, but I think I'm going to try. Working up the courage to order it now.

Based on all the troubles I've seen that folks are having, I'd like to come up with something repeatable and document it so there is another option out there. It's pretty obvious that the old units are becoming more and more scarce.

Thanks,
Wally

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RedBird64
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Re: Replacing MC on a 66 with a dual bowl

Post by RedBird64 » Thu Dec 05, 2019 7:26 pm

As pathetic as it sounds, I have spent hours pouring over different MC's on Ford and GM product using the Rock Auto site. You can look at the shapes of the unit and get all their specs like piston size and port sizes. GM liked to use bigger MC bores as a rule. A bigger bore requires more pedal effort OR more booster (uh oh, I feel an uncontrollable ramble coming on..)

Some GM MC's are really wide where others are narrow like Fords. I suspect the wide body units would have clearance issues for us but the narrow ones might just work out. I need to double check but I seem to remember that both Ford and GM MC's use a 1" stroke.
I think some of the 70's mid size GM cars could be a very good fit for our application.
Here's a good example: https://www.rockauto.com/en/moreinfo.ph ... 94&jsn=470
This MC has 1.125" (1 1/8") Piston where our 65/66 was 1". Becasue that's what Ford used on 65/66/67 Tbirds, I used a 69 Mustang MC with that same 1" bore but now after driving it a while, I feel that a 1.125 would work better. If I changed nothing else, it would require slightly more peddle effort for the same stopping power but could apply more power overall to the discs. All hypothetical though, I don't think the GM MC will just bolt up without some grinding and I couldn't find a Ford MC that's 1.125".

Now the question is, What size booster to use with the above 1.125" bore MC? A 9" would *work* but a double 9" or a 10" would be better if we have room. A 12" might work great but you can have too much boost too. Then the brakes become grabby.
GM used 12" boosters quite a bit for large cars and trucks but combined them with MC's that had even bigger bores (the wide body MC's?). On the other hand, our cars aren't exactly compacts so this combo might work fine (but there's little chance we have space for a booster or MC that big). Of course, there's always the hydroboost route that gets rid of the booster altogether...

Then there's an off the shelf booster/MC setup a lot of the tri-5 guys are using. Something like a dual 7", 8" or 9"?
Oops, there's that fitment issue again..

Oh my, that was a ramble. :drinking:
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

wallyblackburn
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Re: Replacing MC on a 66 with a dual bowl

Post by wallyblackburn » Fri Dec 06, 2019 8:57 am

Not a ramble...more of a...thoughtful dissertation? :)

I do not have the patience for analysis that you do, sir. While it is probably going to take more time and effort in the long run, I am going with the "brute force" approach! I ordered the Inline Tube booster and MC - should be here next week. I also have the Mustang MC on hand. I'm just going to play around and see what the possibilities are.

I'll report back,
Wally

wallyblackburn
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Re: Replacing MC on a 66 with a dual bowl

Post by wallyblackburn » Sun Dec 08, 2019 1:03 pm

Said I'd report back...

Got the universal booster and GM MC...I'm not even going to try. The GM master cylinder is HUGE! The booster could probably be made to work, but the rod sticking out is pretty long, and I'm not sure enough could be cut off unless it was spaced out a bit (making the clearance issues worse).

Anyway, given the above along with the fact that I have already modified the brace for this setup, I just boxed my booster up to send to Power Brake Exchange tomorrow.

I'll let y'all know how it goes with PBE.

Thanks,
Wally

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RedBird64
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Re: Replacing MC on a 66 with a dual bowl

Post by RedBird64 » Sun Dec 08, 2019 5:57 pm

Well that's too bad. There are narrower GM MC's like the one in my link above but even that one looks kinda long.
Hopefully all works out well with PBE!

S
1964 Coupe Wimbledon white/Rangoon Red w/black int. Owned for 42 years. It was my folks car before that (second owners). VTCI # 12013.

jtschug
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Re: Replacing MC on a 66 with a dual bowl

Post by jtschug » Mon Dec 09, 2019 5:07 pm

I got the compact dual MC from Wilwood. I'm also using their disc brake kit for the rear.

With my booster (the bendix unit) it will fit without any modification to the shock tower brace.

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