Single Brake Master to Dual Reservoir on '66 Imp w/Auto Pilot Cruise

[Boomer]

Getting the parts together to upgrade the brakes on my '66 Imp and thought this would be a good time to swap out the master cylinder. However, since the car has the Auto Pilot cruise control unit nearby, it looks tight, at best. I don't have the dimensions of a dual reservoir handy to check measurements.

Wondering if anyone else has done this and, if so, was it a 'drop in' replacement? I thought I read that some of the 66 Imps had front disc brakes, must've still used a single reservoir?

Photos attached showing proximity. Not the best, I'll get more over the weekend.

 

[mr. fix it]

 

[Ross Wooldridge]

Front disc brakes were optional on 66 Chryslers and Imperials and used a special single res master with an extra tall pot for more fluid.

I did a similar swap on my 66 Chrysler with Autopilot.

I had to get a master cylinder with ports on the engine side, so that the lines didn't interfere with the Autopilot brackets. Your car may have room for the lines and the bracket, but mine did not. The master cylinder I used is # 1475 or 101475 depending on the vendor, (application is 68 Charger with discs and 10" rear drums) and looks like this:

Keep in mind that this particular master is for DISC brakes, which my car has. The combination works fabulously.

I don't know if there is a dual res master for drum brakes with the line ports on the engine side. You'll need to do some research.

Then I had to modify the control rod for the Autopilot to go around the front of the new master.

I made a heat shield (you can see a bit of it) to protect the lines from the exhaust manifold, and I also had to notch the Autopilot bracket to clear the edge of the master cylinder lid - this you may not need to do...

You'll also need a distribution block to deal with the dual reservoir master. If you're staying with drums I suggest using one such as this:

62 63 64 Mopar A B C Body Dual Master Brake Distribution Brass Tee Block Valve | eBay

Hope this helps.

 

[Boomer]

Thank you, Ross. That answers another question I had about the availability of something with ports on the opposite side.

I did find one dual reservoir Bendix for drum brakes, but it has ports on the same outboard side. I've never seen 90 degree adapters used on a master cylinder, but I'm not even sure something like those would fit.

Due to my limited knowledge of brake hydraulics, I have to ask - why couldn't your master cylinder set up be used with drum brakes in front? Obviously the reservoir is smaller, and I do know that the front brakes do a lot of the stopping. My recollection when looking at cylinders for the 300 I had was that even with a dual cylinder, it was the proportioning valve that made the difference for discs. As I said, I know little about the nuances of drum/drum vs drum/disc master cylinder uses.

I also noticed some specify manual brakes while others list power. Appearance-wise, outwardly they look the same.

Changing to front discs is not something even on my radar screen at this point, so it might be that staying with the single reservoir is the only option.

Here's a shot of the Bendix dual drum reservoir:

 

[Ross Wooldridge]

Hi there -

Disclaimers first...I am also limited in my understanding of hydraulics and braking systems. I am in no way to be considered a qualified expert! My knowlege is gleaned from learning from experts and careful trial and error.

Please make sure you double and triple check with many licensed pros about any mods you make.

There is a reason for disc masters having a larger reservoir for the front brakes (found at the rear of the master). I believe it's to do with disc pads wearing faster than similar front drums and the reservoir fluid level drops more quickly.

The bore sizes inside master cylinders are also different than those for drum brakes which is why master cylinders can look the same on the outside but vary internally and therefore be quite application specific.

Now that being said, your car is very heavy, already has the Bendix dual diaphragm booster on it to provide more oomph than C body drum boosters, and I would guess that using a disc booster (more oomph again) on a drum system will possibly make the brakes more effective to the point of being touchy. I am not sure.

Generally, discs take more effort to energize than drums hence the development of stronger boosters and narrower bore masters. When modifying braking systems, what one never wants to do is go weaker... that's why I firmly believe that the common use of a drum booster on a disc upgrade is a serious mistake. Sure, it bolts up and functions, but the drum booster doesn't have enough boost to fully energize a disc system and hence can let you down at the WORST possible time. This is why I believe the factory used the stronger booster (used on C body and B body disc systems) on Imperials with drum brakes in the first place. More power available to the braking system.

Using the disc master in theory should be a better thing on your heavy car... however, it's a research question only answered by trying the swap. Try it where you can safely test and retest the braking performance. You may be pleasantly surprised.

 

[Boomer]

That's good to know! Yes, safety is my primary concern here as my wife and daughter will not only be riding with me, I hope my wife will feel comfortable enough to take the car out if she wants to. Knowing that the brakes have been completely rebuilt and are safe is a big step in that direction. A blown rear wheel cylinder somewhere along the way in the delivery process of the car likely contributed to it being backed into a tree when they offloaded. A dual cylinder reservoir would've at least help lessen if not prevented the damage entirely.

The Imperial does have a power booster too, which figures into the bore equations somewhere, I'd bet.

 

[Ross Wooldridge]

What a shame.

Lesson learned I guess. Shoulda been kept on a winch cable coming off the trailer even if it was under its' own power.

 

[Yatzee]

Getting the parts together to upgrade the brakes on my '66 Imp and thought this would be a good time to swap out the master cylinder. However, since the car has the Auto Pilot cruise control unit nearby, it looks tight, at best. I don't have the dimensions of a dual reservoir handy to check measurements.
I did this very conversion on the same car as yours earlier this summer but the cruise was aftermarket and quite a bit smaller. I sourced the master ($78 at Rock Auto) and found that a'68 or earlier was perfect. Make sure as you browse through their listings that you select drum/drum and don't be surprised if you have to enter a different year or model to find one. They all pretty much fit everything Mopar made. Dimensions of the replacement are listed there or on the manufacturers website and everyone knows how to use a tape measure. Installation and piping was a breeze and there is no adjustments on the booster if you stipulate "power drum/drum" when you buy one.. If I find the exact number I will let you know.
Wondering if anyone else has done this and, if so, was it a 'drop in' replacement? I thought I read that some of the 66 Imps had front disc brakes, must've still used a single reservoir?

Photos attached showing proximity. Not the best, I'll get more over the weekend. View attachment 140964 View attachment 140965

 

[Yatzee]

Getting the parts together to upgrade the brakes on my '66 Imp and thought this would be a good time to swap out the master cylinder. However, since the car has the Auto Pilot cruise control unit nearby, it looks tight, at best. I don't have the dimensions of a dual reservoir handy to check measurements.

Wondering if anyone else has done this and, if so, was it a 'drop in' replacement? I thought I read that some of the 66 Imps had front disc brakes, must've still used a single reservoir?

Photos attached showing proximity. Not the best, I'll get more over the weekend. View attachment 140964 View attachment 140965

I did this very conversion on the same car as yours earlier this summer but the cruise was aftermarket and quite a bit smaller. I sourced the master ($78 at Rock Auto) and found that a'68 or earlier was perfect. Make sure as you browse through their listings that you select drum/drum and don't be surprised if you have to enter a different year or model to find one. They all pretty much fit everything Mopar made. Dimensions of the replacement are listed there or on the manufacturers website and everyone knows how to use a tape measure. Installation and piping was a breeze and there is no adjustments on the booster if you stipulate "power drum/drum" when you buy one.. If I find the exact number I will let you know.

 

[70bigblockdodge]

I would not use the disc drum master the reservoir would be fine, but there is no residual pressure valve in rear port. Reason for larger reservoir is as pads wear the piston chases the pad, fluid stays in caliper. Drum brakes always return to anchor pin. The adjuster is opposite the wheel cylinder.

 

[Ross Wooldridge]

There you go - gotta see how much room there is for a regular dual drum master and the Autopilot bracket.

Perhaps you can drill large holes in the bracket to route the lines to the master through the bracket.

 

[Boomer]

Indeed - this is why I ask here. Far smarter people than me, as well as first hand experience. Last thing I want to attempt is reinventing the wheel.

I did this very conversion on the same car as yours earlier this summer but the cruise was aftermarket and quite a bit smaller. I sourced the master ($78 at Rock Auto) and found that a'68 or earlier was perfect. Make sure as you browse through their listings that you select drum/drum and don't be surprised if you have to enter a different year or model to find one. They all pretty much fit everything Mopar made.

Just curious: which side are the ports on? Aftermarket cruise probably doesn't have the space constraints as the original. With the factory Auto Pilot, the unit itself is withing 2-3 inches of the master outboard and the linkage to the throttle wraps around the inboard side, as well as having the exhaust manifold beneath. It *looks* like the drum/drum master from a Coronet, RR, etc might fit the space.

I may end up just staying for the single for now, to get the car legal, safe, and back on the road. Then I'll have a little breathing space to test the fit a bit more.