This sounds like a dumb question, but I can't find anyone asking this elsewhere. I've got a 63 impala (4 drums, power) that I'll be upgrading to front discs and a dual MC. At this point I'm not upgrading rear brakes due to a very likey rear end upgrade sometime in the future (9" maybe?). Can I buy and run a disc/disc MC with rear drums? I realize a drum master with discs is a poor choice but can't find a scenario the other way around. My thought is I'd run a residual pressure valve on the rears and adjust the proportioning valve accordingly. I'd hate to buy two master cylinders within a year or two . Any help appreciated!
I did the same thing on my 64 Belair. Got the MC and the proportioning valve from Master Power Brakes . worked very well. Call there help line and they can tell you what parts you need
Thanks for the reply! Im just glad it's possible! I think I'll go with the disc/disc MC. I think I'm going with a CPP kit, despite some not so great reviews. Hopefully their customer service people are helpful as well.
They look like nice kits. I've been debating on what to do for about two weeks. I'd like dropped spindles. That paired with the MC/booster that CPP sells that moves the unit up and away from my valve covers is kind of swaying me that way (I've got a BBC). They have a "new and improved" 12" kit that uses gm rotors and calipers that I'm telling myself I can't go wrong with. ScareBird brackets with other GM parts seems like another great option. MPB kits look nice, but would tap out my budget pretty quickly.
The difference is in the bore sizes and the proportioning valve that comes in the kit. Get the right MC & prop valve for what you are using right now, not what you might use in the future. In reality, the disc front and drum rear is the best combination anyway, can't really improve over that.
I've done it without issue.. Its best to run a metering valve on the front discs to prevent nose dive and a adjustable portion valve on the rears to prevent lock up. I always used the stand alone units..
Also, bear in mind that the disc conversion may set your wheels out an additional inch. With my 64 the 17's rubbed so I had to raise the front end to compensate.
Done properly...you don't need that ugly booster hanging off the firewall. Just select the correct master cylinder piston size vs the caliper/wheel cylinder size. The brake guys "should..." be able to help with this. Done this more than once with great results. Mike
>>>I'd hate to buy two master cylinders within a year or two . >>> Wow. What do you hate most about buying a disc-drum now and a disc-disc a year or two later? Jack E/NJ
This is how I roll, heads off a lot of problems cobbling an unknown array of parts together and getting them to work. This is the proportioning valve I use quite a bit and has always worked. https://www.summitracing.com/parts/...y9EHsrDq68WwBAfH-hiZvNk0eWeqP0JBoCRZkQAvD_BwE
I realize that sounds kinda cheap, but I'd rather buy something only once if I can get away with it. I've got a two year old, a limited budget, and lots of other crap to buy/fix. I think a disc/drum MC might be what I need... As I figure out what the hell I'm doing a bit more I'm hoping to be a bit more resourceful. I appreciate all the input, seriously. I'm not actually opposed at all to keeping rear drums, however I'm anticipating a rear end swap when I kill my stock rear figure if I have to put brakes on a 9" or something I might as well go disc... The CPP kit I was/am looking at says 3/8" wider than drum. Still wider than some, but less than most kits I've seen. I'd like to keep with the power brakes. I know its not absolutely necessary, but id like to keep them. I'll mull this crap over a bit, buy some stuff, and figure out how it all works! Thanks again!
>>> I've got a 63 impala (4 drums, power) that I'll be upgrading to front discs and a dual MC. >>>a limited budget,>>>I'd like to keep with the power brakes. If it was mine, the only upgrade I'd make is dual master even with an unlimited budget. Jack E/NJ
A master for discs will work perfectly fine for drums, aside from possibly having an internal residual valve the only difference is reservoir size and the disc reservoir will be bigger. Have at it. As said above if mixing and matching components you better understand how to size stuff. Sent from my iPhone using H.A.M.B.
That's the beauty of the adjustable rear proportion valve.. It helps you tie all the different parts together, but not always..
Just get the drum-drum dual master for a 1967 Impala and be done with it. Google "13062016" "master" "front drum" with the quotes and get it from Amazon or RockAuto. Jack E/NJ
I’ve never done a rear disc conversion that was worth the money. I’m back to using the 9” rear with the drums, cheaper, easier to find, etc. Unless you’re going to road race that Impala, set it up for what you’ve got, and put a new rear end in with drums. The advice above regarding the various valves still stands.
With 11" drums, I'd just swap to dual master then clean and adjust the drums. Maybe try Porterfield shoes, they make a very big difference..
I'm doing something similar, I have disc front/rear with a Master Power Brake under floor setup i bought in the mid 90's. The new engine doesn't make enough vacuum to operate the power brakes properly and the rear Lincoln Versailles brake parts are not as plentiful as they once were. I've already bought a set of 11 inch drums to swap for the rear discs and plan on shit canning the booster and making them manual. Now this would give me the disc/disc master cylinder with a disc/drum setup, like was mentioned other than possible bore size and definitely equal reservoir size I don't see a problem with it.
No problem with it, keep pedal ratio in mind if ditching the booster Sent from my iPhone using H.A.M.B.
It never ceases to amaze me how some in this day and age still cling to the notion that drum brakes are somehow better than a properly set up disc/disc system. Often, these same folks insist that bias ply tires are "just better" than modern radial tires. Self energizing drum brakes (virtually every drum brake setup built after 1960) have virtually NO threshold braking ability. When that "oh sh#t" moment arrives and your foot stabs the whoa pedal hard, the drums will lock. Period. It's what they do by design. Just remember..if your rears lock before your fronts, your car MUST change direction while skidding (i,e: front and rear ends swap places). Adjustable prop valves are great...and should be considered mandatory...even on relatively stock vintage vehicles they can help with distribution. Just remember that adjustable proportioning valves do not adjust front to rear pressure differentiation. They ONLY adjust the cut-in point of the rear brakes... or the point at which the rear brake circuit is activated. The full pressure of the pedal will be applied at this point. Someone above suggested that swapping out wheel cylinder sizes will help with true front to rear proportioning. This is absolutely true. A swap to a smaller dia cylinder will increase applied pressure. A swap to a larger dia cylinder has the opposite affect. You should perform a few panic stops once you have your swap done, with an observer to help. If your brakes are set up properly, your front discs will lock up first....but only just barely.
With all respect, what I said was I never did a “conversion” that was worth the money. My first 4 wheel disc were on a 64 XKE in 1966. All the high performance cars I’ve owned, including my daily’s were/are 4 wheel disc. I finally realized I, and most of the companies selling parts don’t measure up to what factories can do. Get into the real hipo brake systems, Brembo, Wilwood, etc. you can do it. But they are not low budget affairs. I simply don’t have the engineering background or experience to make it work by cobbling up parts, and I don’t think I’m alone. I know there are people here that can.
I know it as the split point but thank you Bob, as always good information Sent from my iPhone using H.A.M.B.
You have to look at what is being driven around you these days. 25 years ago I'd convert a '65 Chevy to a dual master and be happy with 4-wheel drums. Today you need to be able to stop as well as a new car will stop, or pretty close to it. If someone in front of you jumps on the brakes in a hard stop, his ABS takes over and the car stops on a dime. If you are that close behind, you need some serious whoa power. Just my 2¢.
ABS in and of itself does help...a lot. However, I recently bought my third Ram pickup. The one it replaced was a 1997 model with disc/drum ABS. It was a great truck that I drove to 260,000 miles and it was still running quite well when i turned it over to my son. The 14 model that I drive now, I was in it 3 months when my son and I took it into Calif for a car show / swap meet. A driver entered the fwy, cut across 4 lanes (from the onramp) and caused a multi-car collision right in front of us. I executed a panic stop from 70 mph. The 4 wheel disc setup hauled that rig to a stop in less than half the distance my old 97 model required. I remarked to my son as we sat there in the aftermath that the truck I handed down to him would NEVER have made that stop. I would have plowed into the ass end of the bimmer in front of me that rear-ended the person in front of him... A fair enough point, and for what it's worth, I didn't mean for it to seem as though I was picking specifically upon you, Miker98038. There were a number of folks on this thread that lamented that disc swaps just weren't worth the effort. As for engineering I can see your point there, too, but although I am a mechanical engineer by trade, I strongly believe in maintaining a car with as many factory designed components as possible. I read a lot of car publications and those that offer extensive tech articles (i,e; like "Mopar Action magazine") have been very useful in this quest. I have converted several of my cars to front disc using their tech, including the car in my avatar pic, and just completed a rear disc swap on my 1970 challenger (I know...not a HAMB car, but you see where im going with this). I pilfered the entire setup from a wrecked Jeep Liberty. Complete with 11" rotors, calipers and drum-in-hat parking brakes, the entire setup cost me $170 bucks with new pads. A couple of minor modifications were all that was required. The best part is it's all factory stuff. The 64 is getting it next. I just need to swap out the tapered axle nightmare thats back there now. There are a lot of people out there re-engineering this stuff for us...not just for Chryslers, but other makes as well. You just have to ferret out the proper articles, web sites or interface with the right people. Our cars are much larger and heavier than most modern rides. That makes it all that much more important that we update our brakes to keep all that flying steel from being destroyed. After all...it's usually not the classic car owner that causes such accidents. It's the other guy...usually in some late model eurojap sh#t box. Peace
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