Need opinion from those that KNOW.

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nodemon

nodemon

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I'm trying to replace my master cylinder. It's a manual, front and rear 10" drum setup..
My OEM M.C. has 2 equal reservoirs... I thought while doing brief research that 2 equal on the all 4 drum and a small and bigger combo reservoirs for disc. Inline Tube sales is trying to sell me the latter, the small front / larger second reservoir combo. Anyone know for sure..? Does it make a difference..? Also, he couldn't tell me if it was for 9" or 10" drums...which I thought made a difference.
T.I.A..
John
 
nodemon said:
I'm trying to replace my master cylinder. It's a manual, front and rear 10" drum setup..
My OEM M.C. has 2 equal reservoirs... I thought while doing brief research that 2 equal on the all 4 drum and a small and bigger combo reservoirs for disc. Inline Tube sales is trying to sell me the latter, the small front / larger second reservoir combo. Anyone know for sure..? Does it make a difference..? Also, he couldn't tell me if it was for 9" or 10" drums...which I thought made a difference.
T.I.A..
John
Click to expand...
The disc/drum master won't have a residual valve in the front brake (rear) port. May or may not be an issue, but the factory put them in there for a reason. The extra volume wouldn't be an issue, you just have extra fluid.
The biggest thing is going to be bore size, make sure it matches or is a step smaller than OEM.
9 or 10 (or 11) inch brakes was also one of the determining factors in master cylinder bore and wheel cylinder sizing.
 
I agree. You can find external residual valves, and some systems do fine without them. The reason for them is, that wheel cylinders can sometimes allow air to enter past the seals as things retract, and the purpose of the valve is to maintain a small positive pressure in the system so that does not happen.

I do not for certain know how you would tell a LACK of a valve, but if you are VERY CAREFUL, you could take a BLUNT probe, and GENTLY enter it into the disc side and find that you could easily push it through the fitting and down into the internal passage. If the drum side has a valve, there will be a small rubber diaphragm in there which will stop the probe. DO NOT use anything pointed and do NOT force it.
 
Only if you are doing a "correct" restoration does it matter. If the dual M/C (both styles) will work if set up for four wheel drums.
 
Good question.

I wouldn't spend money for the disk set up master cylinder when all it should be is a common drum master cylinder.
See the pdf here
Replacing Master Cylinder

No reason to have to guess whether the salesman or some stranger on the internet has a leg to stand on or is making it up as we type. In addition to the usual service manuals and parts books, Chrysler explained the differences in some of the sessions here
Master Technician Service Conference - Chrysler's Training for Mechanics

edit: changed first link to thread with a valid link to Brad's article pdf
 
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1967 parts book shows no difference in MC based on whether the drums are 9" or 10"
2808 599 for all drum systems A, B and C body
1700169565811.png
'

1969 the same
1700169755257.png


1970 shows a new part number but no differnce with respect to drum brake diameter.
 
I replaced mine last year, 69 Barracuda with manual 10" drums. This was as close to original I could find. It has the bolt on cover as seen at Summit. Works great!

Raybestos MC36221 Professional Grade Brake Master Cylinder​


Amazon product ASIN B000C73LXY
 
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I guess maybe I should have given more info... not sure if it makes a difference to some responses, but this is for a 1972 Demon 318
 
4spdragtop said:
I have equal sized reservoir, and factory front discs. Zero issues with my brakes.
Click to expand...
Agreed. Did a Summit brand booster and master disc kit. Had the GM master and had problems with brake drag to the front discs.Front and rear reservoir same size.BUT,,
Guess what. Had a residual valve in it. Also got a master for a 78 Chevy Malibu disc brake car and it had same size reservoir front and rear. Gotta be careful with aftermarket parts.You never know what you will get.
 
Reservoir was on when we bought car so no idea on make/part#. I have a correct #'s oem one I may install, but honestly I have had zero issues so why mess with it lol.
Darter6 said:
Agreed. Did a Summit brand booster and master disc kit. Had the GM master and had problems with brake drag to the front discs.Front and rear reservoir same size.BUT,,
Guess what. Had a residual valve in it. Also got a master for a 78 Chevy Malibu disc brake car and it had same size reservoir front and rear. Gotta be careful with aftermarket parts.You never know what you will get.
Click to expand...
 
I've read in a coupla places thru the decades, some others too, likely, that the reservoir sizes had more to do with having enuff fluid to get thru a shoe/pad lifetime.
Small reservoirs, = wheel cylinder capacity when shoes fully worn, plus a little bit.
Disc brake same, enuff fluid capacity for a full set of pads front(big), wheel cyl fluid capacity rear (small)
Bigger piston caliper, bigger reservoir yet, - more fluid so not to run out before pads gone.
So, if you popped the m/c cap during an oil change, and found the reservoir near empty, rubber condom hanging outta the cap, - chances are it needs brakes or look for a leak.

If you plan on running your car thru a full set of pads or shoes, without checking your fluid levels, we're talking years here, - then there's something wrong with you or your service-person that needs a boot up his/her *** . imho

Piston size/travel is only pertinent value, (with residual valve for drum when nec) they all pretty much interchange otherwise .
 
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CFD244 said:
You can buy kits for them if you want to rebuild yours.
Click to expand...
I consider myself to be a pretty good mechanic, but I have never had any luck rebuilding master cylinders. The two I tried were before the internet got really popular; thus before YouTube. I don't know what I did wrong. Oh well!
 
nodemon said:
I guess maybe I should have given more info... not sure if it makes a difference to some responses, but this is for a 1972 Demon 318
Click to expand...
I would not waste my $ on anything from in-line everything they sell leaks or in incorrect trust me I know from experience call Cass from DR.DIFF you will get all your correct parts and answers imo and experience
 
74 360 dart sport said:
I would not waste my $ on anything from in-line everything they sell leaks or in incorrect trust me I know from experience call Cass from DR.DIFF you will get all your correct parts and answers imo and experience
Click to expand...
I talked to Cass after so many recommendations.. said they couldn't help.
Strange..

Screenshot_20231117_081512_Chrome.jpg
 
If there is one, could you give the casting number on the bottom of the master cylinder.
 
That is a casting number. The Chrysler part number for it is 03461184 I Did a search at Rock Auto. More Information for RAYBESTOS MC36308
Buyer's Guide : RAYBESTOS MC36308 Master Cylinder
DODGECHARGER1971-1972
DODGECORONET1971-1972
DODGEDART1971-1972
PLYMOUTHBARRACUDA1971-1972
PLYMOUTHCUDA1971-1972
PLYMOUTHDUSTER1971-1972
PLYMOUTHGTX1971
PLYMOUTHSATELLITE1971-1972
PLYMOUTHSCAMP1971-1972
PLYMOUTHVALIANT1971-1972
Ignore my Canadian pricing. lol
 
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You have the original master cylinder, so which every way you proceed keep your old master.
Chrysler used one of their cost saving ideas relating to master cylinders. They had two housings, one with two equal size reservoirs and one with a large and small reservoir.
By the mid seventies all of the same size reservoirs were sold and they were replaced with the disc style master cylinder. So if you went to the dealership with the original style master, they sold you the disc type master as a replacement. It was cheaper for Chrysler to have different bore sizes while still using one housing. What's really confusing is they both had the same part number. Some of the aftermarket master cylinders did the same.
Looks like Raybestos still has the original style.
If you decide to rebuild, then this is the proper kit.
www.ebay.com

NOS 1971-74 Mopar Power Drum Master Cylinder Repair Kit 3579257 | eBay

Fury I; Fury II; Fury III; Sport Fury; 1971; 1972; 1973; ALL. Barracuda; Cuda 340; 383; 440; 440-6; 1971; 1972; 1973; 1974; ALL. Polara; Polara Custom; Monaco; 1971; 1972; 1973; ALL. Challenger; Challenger Rallye; Challenger R/T; 1971; 1972; 1973; 1974; ALL.
www.ebay.com
 
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nodemon said:
I talked to Cass after so many recommendations.. said they couldn't help.
Strange..

View attachment 1716167557
Click to expand...
I bought my MC from Rock Auto for my 69' that had 4 wheel 10' drum brakes and added disc Kelsey Hayes brakes from a 70' and it works fine. Have not tried it on wet roads yet. Did not add a PP valve yet because everything seems to work fine.
 
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