Wrong Master Cylinder?

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kittypancake

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Do front disc/rear drum master cylinders have a small front reservoir and large reservoir?

I am putting KH 4 piston discs on the front of my 1972 Valiant. I ordered front disc/rear drum master cylinder from Rockauto way back when. The one I received has 2 equal reservoirs, but the port sizes are different than the original one.
 
Usually yes, they are big-N-little. I believe my MC is similarly coded for frt and rr lines. Just make sure the residual valve is only in the port that goes to the drums, usually the frontmost reservoir,closest to the rad.
 
been through this my self//a long feed was done here//the only accurate vender was (SUMMIT) racing !!!!! pay the extra !!! it will save you the aggravation!!
 
jazak5 said:
been through this my self//a long feed was done here//the only accurate vender was (SUMMIT) racing !!!!! pay the extra !!! it will save you the aggravation!!
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Sadly, I had already bench bleed and painted it before I realized it was wrong, and I don't know know if I still have the box. I checked to see if I ordered the wrong part. The one I ordered CLEARLY states front disc/rear drum, non-power, which is what I want.
I sent an email to Rockauto to see what, if anything, they will do for me...we'll see what happens...
 
kittypancake said:
Sadly, I had already bench bleed and painted it before I realized it was wrong, and I don't know know if I still have the box. I checked to see if I ordered the wrong part. The one I ordered CLEARLY states front disc/rear drum, non-power, which is what I want.
I sent an email to Rockauto to see what, if anything, they will do for me...we'll see what happens...
Click to expand...
Addendum...the one I ordered IS the one I received...right description, wrong part
 
It will work just fine. Don't beat yourself up over it. Just check the reservoir fluid level more than once a year and you will be OK; the guts and the operation of it are the same, so long as the pushrod fits and stays put.
 
I have a '72 Valiant also with factory disc brakes . I deleted the booster and installed a m.c. from a '73-76 Valiant/Dart without power . The front port in m.c. goes to the rear brakes and the rear port goes to the front brakes in both applications . The distribution block on the fenderwell is also the same for both . The front port in the m.c. goes to the top port in the block . The exit port in the block is facing the rear . The rest you can figure yourself . The reason the resivoir on the rear is larger is because disc brakes require more volume than drums . BTW all brake lines are 3/16ths . Hope this helps , good luck , Tom
 
383Scampman said:
I have a '72 Valiant also with factory disc brakes . I deleted the booster and installed a m.c. from a '73-76 Valiant/Dart without power . The front port in m.c. goes to the rear brakes and the rear port goes to the front brakes in both applications . The distribution block on the fenderwell is also the same for both . The front port in the m.c. goes to the top port in the block . The exit port in the block is facing the rear . The rest you can figure yourself . The reason the resivoir on the rear is larger is because disc brakes require more volume than drums . BTW all brake lines are 3/16ths . Hope this helps , good luck , Tom
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This does help a bit
 
Recently converted my original (still working) 72 Demon KH brake equipped disc master cylinder from this equal reservoir style

P1030323.JPG



To this 73+ style. The pedal effort in braking is much easier & port sizes were exactly the same....

P1030326.JPG
 
6pk2goDemon said:
Recently converted my original (still working) 72 Demon KH brake equipped disc master cylinder from this equal reservoir style

View attachment 1714985975


To this 73+ style. The pedal effort in braking is much easier & port sizes were exactly the same....

View attachment 1714985976
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So...your original 4piston disc master cylinder was the equal reservoir style? If that's the case, perhaps I don't have the wrong master cylinder. The 1972 Chrysler Chassis Manual says disc and drum masters have different bail, cap, and gasket...they didn't add an "except for when they don't" disclaimer...
 
kittypancake said:
So...your original 4piston disc master cylinder was the equal reservoir style? If that's the case, perhaps I don't have the wrong master cylinder. The 1972 Chrysler Chassis Manual says disc and drum masters have different bail, cap, and gasket...they didn't add an "except for when they don't" disclaimer...
Click to expand...

No, KH disc brakes did not have equal reservoirs from the factory. You need to realize that the brake parts listings that RockAuto and everyone else uses are incorrect. Sometime in the dark days of Chrysler, they experienced some kind of data dump, and the part number records for A-body brakes 67-72 were corrupted (possibly others, but these are the ones I am familiar with). It's why certain applications can be impossible to find, even though the parts exist -- they just aren't linked to that application. Your MC should look like the one labeled 73+ above (big toward the firewall, small in front). The A and B-body disc brake MCs did not change over the entire period, in appearance -- only the bore diameter changed, with variations per year, model, and power vs manual. The important difference between disc/drum and drum/drum MCs isn't the reservoir size, it's the presence of a residual pressure valve in the drum ports -- you do not want this in the disc port or it will cause the pads to constantly rub.
 
kittypancake said:
Do you remember the part#?
Click to expand...

The Raybestos one I wanted is a MC36406, but I couldn't find one locally so I purchased a new one from O'Reilly's that crossed to their #BHH NMC11145. This a new MC, NOT a rebuild unit. I won't buy a rebuilt MC


kittypancake said:
So...your original 4piston disc master cylinder was the equal reservoir style? If that's the case, perhaps I don't have the wrong master cylinder. The 1972 Chrysler Chassis Manual says disc and drum masters have different bail, cap, and gasket...they didn't add an "except for when they don't" disclaimer...
Click to expand...

Yes, KH disc manual brakes with the equal reservoir MC as shown above. It was still working fine, but I wanted better/easier pedal pressure.
 
mvh said:
No, KH disc brakes did not have equal reservoirs from the factory. You need to realize that the brake parts listings that RockAuto and everyone else uses are incorrect. Sometime in the dark days of Chrysler, they experienced some kind of data dump, and the part number records for A-body brakes 67-72 were corrupted (possibly others, but these are the ones I am familiar with). It's why certain applications can be impossible to find, even though the parts exist -- they just aren't linked to that application. Your MC should look like the one labeled 73+ above (big toward the firewall, small in front). The A and B-body disc brake MCs did not change over the entire period, in appearance -- only the bore diameter changed, with variations per year, model, and power vs manual. The important difference between disc/drum and drum/drum MCs isn't the reservoir size, it's the presence of a residual pressure valve in the drum ports -- you do not want this in the disc port or it will cause the pads to constantly rub.
Click to expand...

I respectfully beg to differ as my Demon is an original 72K mile car.....Spent some time researching too!! It doesn't really matter as I replaced my working MC for one that works better for ME :D

What is the correct master cylinder for manual disc
 
-The KH m/c on my 71 Demon parts car was a big-n-little. I parted it out in about 75. Since I was 3rd owner, I can't say it was original. I rebuilt it and ran it on my clone S for a while, but decided I wanted a smaller bore. I mothballed it in about 2002ish. I like the feel of the replacement,15/16 bore with a 73 booster.
-The KH m/c on my 68 Formula S car is also a big-n-little. It came into my possession in 1998. It had been languishing in the bush for over 20 years. The original owner crashed and rolled it and died shortly afterwards. I am 3rd owner on it too, counting the bush-owner I bought it off, who never did anything with it.
-The KH m/c in my 70 Swinger 340 was a big-n-little as well. I bought that one in the fall of 1970. I was 2nd owner. That car had about 11,000 miles on it when I purchased it from a slightly older than me fellow who had just become a father, and needed the money,of course. I still remember the serial number!
-The KH m/c in my 70Duster was a big-n-little. I bought that one as a roller,complete less engine. I only owned it for a short while as someone came along and made me an offer I couldn't refuse.
- My 1969 FSM, shows the KH m/c to be a big-n-little; page 5-56.
- jus saying...
 
So...my heads spinning...does anyone know how to see if there is a residual valve in the rear port WITHOUT destroying the tube seat?
...I should probably just get a big-n-little
 
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