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15/16" MC with 2.75" calipers and 15/16" wheel cylinders ?

The line pressure will be higher but the pedal will move further. That size master could also over brake a street car with a dual diaphragm booster especially the drum rears.
I have no experience with the combo but (guessing) it will probably work brakes wise very well but you may have to sort out rear brake pressure and an abnormally low pedal that you will not be able to rectify.
It may be safer to use a 1 inch bore or the factory size with the Bendix booster was 1 and 1/8 inch.
 
I put a 15/16ths" bore MC on my 66 Belvedere with the stock wheel cylinders and my pedal effort was reduced but like steve said, pedal travel increased some. IIRC the stock single pot MC was 1"......but the replacement was a dual MC from a 69 Valiant. The 69 was a parts car and well, it had a fairly new MC on it so I adapted it to the B body. Only things that needed changing were the lines and the strike for the BL switch.
 
My current setup (the way it was went I bought it) is....8" dual aftermarket (china) booster/ with a 1.125" MC, 10.9" rotors, 2.75" slider calipers, All new hoses. an adjustable pressure valve to stock 10" drum brakes that have 15/16" wheel cylinders.
I've replaced the calipers and wheel cylinders, blead the system several times. The car has a very Hard pedal. The car will stop, but not fit to drive safely. I'm going to do more checks on the booster ( I have 17"-18" of vacumm ). But I know that the 1.125" MC bore can not be helping my problems ! The car is a 62 Plymouth Fury wagon. Would like to keep the power brakes.....But if all else fails... I will convert it to Manual disc/drum system.
 
I often use 1 1/8" master with 2.5" calipers and they work well so your 2.75" should be a little softer. Maybe your booster is bad?
Going to a smaller master will soften the feel and the pedal will travel farther down also
If the booster is absolutely good then go to a 1" master
 
I often use 1 1/8" master with 2.5" calipers and they work well so your 2.75" should be a little softer. Maybe your booster is bad?
Going to a smaller master will soften the feel and the pedal will travel farther down also
If the booster is absolutely good then go to a 1" master
Thanks for your reply, The booster might be bad . This conversion kit was install by P.O. and Ebay kit :( , so I'm trying for fix the problems, and make to system safe)
 
I have a setup pretty close to this in THIS car:
XH 654.jpg


XH 650.jpg


XH 629.jpg


15/16" manual master cylinder, Aspen/Volare 2.75" single piston front calipers and 10" drum brakes with unknown size rear wheel cylinders. It stops quite well.
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Edit...The rear brakes are from a 1987 Chrysler Fifth Avenue. A Rock Auto search stated that they are 15/16" size.
 
I have a setup pretty close to this in THIS car:
View attachment 1169362

View attachment 1169363

View attachment 1169364

15/16" manual master cylinder, Aspen/Volare 2.75" single piston front calipers and 10" drum brakes with unknown size rear wheel cylinders. It stops quite well.
****************************************************************
Edit...The rear brakes are from a 1987 Chrysler Fifth Avenue. A Rock Auto search stated that they are 15/16" size.
What master cylinder is that ?
 
It is an aluminum one from Dr Diff. 2 bolt mount with an adapter.
 
It is actually a '70....

jiggy F 14.JPG


Yeah, I got the adjustable pushrod to account for the thickness of the 4 bolt to 2 bolt adapter.
 
i've been thru this and found the 15/16" master cylinder doesn't have enough volume per stroke to feed the large 2.47 piston least wise a 2.75. maybe you'll get lucky, but i didn't. currently i use a 1.031" master cylinder with 2.47 pistons. pedal doesn't go to the floor with this set-up vs the 15/16" during hard breaking, but still nothing to feel good about. if i could do it over i'd never use a factory type caliper.
 
i've been thru this and found the 15/16" master cylinder doesn't have enough volume per stroke to feed the large 2.47 piston least wise a 2.75. maybe you'll get lucky, but i didn't. currently i use a 1.031" master cylinder with 2.47 pistons. pedal doesn't go to the floor with this set-up vs the 15/16" during hard breaking, but still nothing to feel good about. if i could do it over i'd never use a factory type caliper.
I can see that the 15/16" MC would provide less fluid to the system. Yet Kern Dog's 70 Charger is using the 15/16 MC and he says "it stops quite well" I sent an Email to Dr. Diff to see what he has to say about MC bore size . What came with 2.47" calipers ? the only sizes I know about are 2.60" and 2.75" .
 
I have a setup pretty close to this in THIS car:
View attachment 1169362

View attachment 1169363

View attachment 1169364

15/16" manual master cylinder, Aspen/Volare 2.75" single piston front calipers and 10" drum brakes with unknown size rear wheel cylinders. It stops quite well.
****************************************************************
Edit...The rear brakes are from a 1987 Chrysler Fifth Avenue. A Rock Auto search stated that they are 15/16" size.
I have the same set up. Looking to replace the front brake hose. What length are yours.
 
I've found it's best to keep the caliper and wheel cylinders the same as what was on the donor vehicle.

If you do that, you eliminate a variable.
 
My current setup (the way it was went I bought it) is....8" dual aftermarket (china) booster/ with a 1.125" MC, 10.9" rotors, 2.75" slider calipers, All new hoses. an adjustable pressure valve to stock 10" drum brakes that have 15/16" wheel cylinders.
...
The car has a very Hard pedal. The car will stop, but not fit to drive safely. I'm going to do more checks on the booster ( I have 17"-18" of vacumm ). But I know that the 1.125" MC bore can not be helping my problems ! The car is a 62 Plymouth Fury wagon.

I know this is an old thread, but jic it's still an issue...

Sounds exactly like my 65 Coronet setup. Brakes were swapped from a 70s Mopar before I bought it. MC, calipers, etc. the same as yours, except a stock pressure valve/distribution block.

I had a similar experience, due to lack of boost. The OEM booster was always marginal with discs (single diaphragm.) When I swapped the motor not enough vacuum = hard pedal effort, no stopping! I swapped to a 68 dual booster with a 65 pedal rod added by the rebuilder. Did the trick!

Couple of thoughts. Make sure the booster check valve isn't leaking. They do fail and then the booster has no vacuum! You won't hear it because there's no internal leak.

Also the early Bs had that long booster rod that bolted directly to the pedal arm. If the PO didn't measure this and/or adjust the new rod to the right length you've got much less length = won't fully actuate the booster = less braking. Should be obvious, though, if the brake pedal is as low or lower than the gas...

Finally check the booster to MC adjustment. The booster pushrod should be adjusted to the MC piston, leaving just a slight gap (FSM or booster manufacturer will say how much) to avoid brake dragging.

Good luck!
 
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