Disc brake swap - master cylinder question.

[Belvedere-II]

The spindles and calipers are 73-76 A body, and the first master cylinder I got was for a 71 B body with a very small front (rear brake) reservoir. We had problems, so I got a 75 A body "power brakes, front disc, rear drum" master cylinder. I have an adjustable proportioning valve in-line with the rear brakes and even adjust out fully (less brake) the rear brakes drag. The drum slides off without much effort, and the shoes are in good shape. The rear wheel cylinders are new (65 B body replacemnt), and the problem I'm having is that when I hit the brakes hard, the fronts don't lock up at all.

On level ground, if I come to a stop by normal means... not pushing the brakes hard... the car does stop okay and it doesn't seem to be a problem. If I brake hard and come to a stop, when I take my foot off the brake pedal the car will not move forward under idle until after a couple seconds (did this with the other master cylinder, too.

Since the car had a single reservoir and 4 wheel drums, I'm guessing that the tee, or 'distribution block', for the brake lines was just a block with four tapped holes (single inlet, RF, LF, Rear lines) and that it wasn't a "vavle" of any sort. Would that be correct? Or would you think that distribution block had something in it to adjust brake line pressure between front and rear?

 

[BBDart]

Yeah I deleted the brass dist block and put in the prop valve from a 73 up A body.sounds like it might be coming from the master like it's slow releasing the rears.The master I used is for a manual disc drum 71 340 dart.

 

[Belvedere-II]

I'm on my second master cylinder; one being defective I can see that happening, but two is hard to believe, especially since I'm having the identical problem. I guess I'll try to find a proportioning valve and see if that will help. This is just bugging the crap out of me.

 

[Belvedere-II]

Wow. I just took my car to a local Sears automotive for an alignment because I can't seem to find a shop that will work on a 65 plymouth. I asked the guy to check my brakes, and he backed the shoes out a little but they still are over heating. He had all four wheels off, and then told me he can't really work on my brakes because they aren't "stock". So he did the alignment and I noticed that my front end was clunking a lot. I put the front end in the air, removed the wheels, and gee... how did he not notice that BOTH caliper brackets were about to fall off the rotors??? The bolts were coming out, one was backed out almost all the way.

First questions you're going to ask is who bolted them on, and unfortunately it was a friend who helped me do the conversion. He thought he had put loctite on the bolts, but I didn't see any. He's a good friend and **** happens, so I'm not going to bust his balls... no harm, no foul. But I'm still amazed that the mechanic checking my brakes never noticed it!!

I think I'm going to officially drop back ten and punt.

 

[BBDart]

Wow that could have got ugly real fast!!..glad you caught it,good luck on getting this figured out.

 

[Belvedere-II]

Thanks BBDart... me too.

 

[tazxprs]

Had the same prob on my 65. Switched to a 79 D150 mc. Helped a lot.

 

[rgoss_10]

Here is an in depth article on what you need. I feel you will get a straight answer and can make your conversion an ez task. I'm going this route with my 65 Dodge...

http://www.moparaction.com/tech/archive/disc-main.html

I'm swapping the front drums to discs and have a couple questions. I'm using the later A-body spindles and calipers (11 inch rotors, slider calipers) and swapped in a Master Cylinder from a 71-75 B-body.

My questions are:
1. Does it matter if the caliper is to the rear of the spindle, or does it have to be towards the front? I've heard both, but anyone who has knowledge please help.
2. When replacing the master cylinder on my 1965 power booster, there is a spacer that was on the old single reservoir cylinder, does it stay or get removed?
3. When installing the new master cylinder, should the booster pushrod be firm against the MC piston, or barely touching it? Without the spacer removed, the master cylinder piston gets pushed in a little with the pushrod, with the spacer, it doesn't come in contact with the piston.

I know there are articles out there, but of the ones that I've read (one was an E-body, the other was a later B-body) none of them clearly defined the details on the master cylinder. I got a new one from Rock Auto (part # 10-1515) and currently the brakes work but if I slam them on I don't get wheel lock up. It stops, but not as good as I would have hoped.

We used an adjustable proportioning valve for the rear, and I have new wheel cylinders on the drums. We bled the brakes completely, but still not as firm as I would have hoped. (the MC was bench bled on the car to get all air out of system).

Thanks for any advice/suggestions on this.

 

[Belvedere-II]

Believe me, I've read that article numerous times, and others as well. The problem is there are tons of Master Cylinders that people have been recommending that "worked" for them, but I've had the same issue with two different recommended MCs. That article referenced above "highly recommends" the adjustable proportioning valve like the one I have installed, and I followed the advice (except I do have my calipers to the rear of the knuckle instead of the front, but the bleeder is at the top like it's supposed to be.

Here's a question maybe someone might know: the factory distribution block on the four-wheel drum cars: is it just a block with four bosses in it or is there a valve or something in it?

Thanks

 

[67 coronet]

Believe me, I've read that article numerous times, and others as well. The problem is there are tons of Master Cylinders that people have been recommending that "worked" for them, but I've had the same issue with two different recommended MCs. That article referenced above "highly recommends" the adjustable proportioning valve like the one I have installed, and I followed the advice (except I do have my calipers to the rear of the knuckle instead of the front, but the bleeder is at the top like it's supposed to be.

Here's a question maybe someone might know: the factory distribution block on the four-wheel drum cars: is it just a block with four bosses in it or is there a valve or something in it?

Thanks

should just be a diverter block with no valving if off an all drum car.

 

[Belvedere-II]

Hmmm. well there goes that theory. my friend put the line in from under the car while I was bending the brake lines and he put the rear line 'in' to what was previously an 'out' line to a front brake. But the car was all drums and the only reason we kept that block is becuase we couldn't remove the rear line from it, so we plugged two outlets and fed the rear brake line into it. Thanks.

I wonder if the valve I installed is just defective?

 

[67 coronet]

could be.i had a similar problem with line removal and solved it with a bit of heat from a butane torch.worked great.if your lines are seized it could indicate internal corrosion and be part of your problem.wouldnt cost all that much to replace the old metal lines if you cant find any other way to solve your issue.

 

[Belvedere-II]

Well, here's the latest: I replaced the adjustable proportioning valve and same problem. I've talked to a couple shops, and send diagrams of my setup and I've been told "everything is done correctly". So I'm going to try to blow out the rear brake like and replace the rear hose. Something's binding up in the rear and I have no idea what it is.

I know my front brakes are working, actually feel a little better now, and tried stopping using only the E-brake. Definitely getting good grip on the calipers now. But I can't figure out why the rear brakes are binding and holding.

I'll keep you posted. Thanks for all the input and suggestions!

 

[furyus]

This seems to me that it's not that the back brakes are a problem, but the front. I have had this same problem. If I try to powerbrake the car(64 Sport Fury) it will push the car even with a high stall converter. It just doesn't stop like it should.Slowing down from high speeds is scary.Takes a long time. So I went with the larger rotors (11 3/4)and the larger slider calipers(76 i think) and had no pressure. 15/16 bore MC. went to 1 1/32 MC and I have my pedal back, but the fronts just don't apply enough pressure. Rears are 11 inch drums with correct WC and new flex lines. Has been this way for years. Still have the 73 Duster prop valve that's been in since the conversion. If anyone has had this problem and fixed it I would also like to hear. I've been thinking of power brakes, but the system must have worked on the Duster it came off of, so, what's changed?

 

[Belvedere-II]

This seems to me that it's not that the back brakes are a problem, but the front. I have had this same problem. If I try to powerbrake the car(64 Sport Fury) it will push the car even with a high stall converter. It just doesn't stop like it should.Slowing down from high speeds is scary.Takes a long time. So I went with the larger rotors (11 3/4)and the larger slider calipers(76 i think) and had no pressure. 15/16 bore MC. went to 1 1/32 MC and I have my pedal back, but the fronts just don't apply enough pressure. Rears are 11 inch drums with correct WC and new flex lines. Has been this way for years. Still have the 73 Duster prop valve that's been in since the conversion. If anyone has had this problem and fixed it I would also like to hear. I've been thinking of power brakes, but the system must have worked on the Duster it came off of, so, what's changed?

I'm not sure if I'd agree that it's the fronts dragging because when I drive the car for about a half hour the rear shoes fry and the brakes are smoking (kind of a tell tale sign it's the rear! LOL) It's gotta be something, and please don't take my responses as disagreeing, just thinking out loud...

Thanks1

 

[furyus]

No, I was saying I think the rears are working, maybe need adjusting, but the fronts aren't doing their part. The rears could be smoking from doing all the work.

 

[Belvedere-II]

No, I was saying I think the rears are working, maybe need adjusting, but the fronts aren't doing their part. The rears could be smoking from doing all the work.

Oh, I see, sorry.
I took the car to a dirt road and at low speed slammed on the brakes. The fronts locked and the rears didn't, which makes this whole scenario even more baffling. I'm replacing the rear rubber line this weekend, and will look harder at the rear to try to figure it out. I'm also thinking of converting to manual instead of power... cheaper than replacing the booster.

 

[furyus]

Yeah I'm confused now too. I thought your problem was like mine in that I think I need more clamping force to stop my car sooner. Oh well.

 

[67 coronet]

just to address everything,check how smooth the contact points are where your rear shoes contact the backing plate.should be smooth and have a small amount of anti seize lube there.can cause binding in certain situations.

 

[Belvedere-II]

Thanks, I'm going to pull the drums off this weekend and see if I can figure anything out. I really hate the fact that most shops around here won't touch anything older than 1980, and those that will won't touch the brakes because they aren't 100% stock. I need to find an old shop that works on REAL cars, not just cars that you can plug a module into to figure out what's wrong! lol

Maybe I'll just get a $400 rear disc kit from eBay and be done with all this drum brake crap!

What do you think of this kit?
http://www.ebay.com/itm/mopar-8-3-4...t=Vintage_Car_Truck_Parts_Accessories&vxp=mtr