Technical Master Cylinder Question(s)

For years, my go to MC has been the Raybestos #36440. Fitment is for the mid 70's Granada, Comet, Maverick etc. with disc front/drum rear, manual brakes (I don't like power brakes for a hotrod). The bore is 15/16" (.938) which gives a good pedal feel with 6-7:1 pedal ratio.

Well, I went to Rock Auto to order another and Raybestos is no longer making this MC. They do have a #36445 for power brakes with the same size bore. What other relevant differences might there be between a power and manual brake MC?

Rock Auto does list the manual brake MC from manufacturers like "Dynamic Friction" and "Quality Built"...but frankly given the quality of recent aftermarket parts, I like using name brands like Moog, Raybestos etc.. Any thoughts from the HAMB brain trust?

I did look at the Chevrolet Nova MC's for similar years (disc front, drum rear, manual brakes) and it shows a 1" bore...I know that'll result in a slightly heavier pedal feel.

 

The difference is probably the depth of the hole that the rod goes into, manual = deep, power = shallow, the deep preventing the rod from dropping out, which isn't possible in the enclosed, powered application.

Chris

 

The power brake mc has a shallow dimple in the back of the piston instead of the deep hole used on a manual one to hold the rod.

I wouldn't be to concerned about the odd RockAuto brands. They are probably made in the same factory as the brands you are familiar with. I might pull one apart and check for corrosion before I install it, just to be safe.

 

Thanks for the info...I wonder if the hole in the piston for the rod could be bored deeper to provide security against the rod dropping out? Might need to purchase one and experiment.

 

My experience with Bendix masters for Fords are deep push rod bores on power masters. I'm sure this has to do with booster designs; guided/non-guided booster pins. Just be sure the master you choose has a deep primary bore if the manual push rod will not be retained in the bore.

 

Hi Tim, I am using Speedways #910-31425. It has a 1" with bore stainless steel sleeve. Stock 40 Ford brake pedal . I purchased it in 2012 It is used with a 11 disc front and ford drum brakes in the rear I have used it for 8 years with no problems. Pedal pressure is very satisfactory.


Sam

 

You could make guide to keep the rod from dropping out from the shallow hole master.

 

I'm using the 70's Corvette disc/drum manual master in my '39 Chev coupe and works great with 11" front rotors and Ford factory 8.8" rear drum setup.

 

I thought Corvette went from drum/drum to disc/disc in '65...I'm not aware of a Corvette disc/drum combo. Glad to hear that it worked well for you though.

Thanks for that suggestion...I ordered 3 of the "Quality Built" brand masters (1 for current build, 1 for next build and 1 as a spare). We'll see how they work, fingers crossed.

Thanks Sam, that'll be my back-up plan.

 

JFYI, Corvette never ran production disc/drum; Drum/drum to '64, then disc/disc in '65.

 

Have a bunch of master cylinders in storage, but I’d need some time to get to them to check numbers. 99.9% sure there are two MC36440 NIB ones.

 

To close the loop...I ordered the "Quality Built" brand MC from Rock auto. They are indeed made in China as suspected. The MC looks good and is made of aluminum.

 

For all the slagging China gets, they seem to make fairly decent castings.
It's the finish machining that needs to be carefully checked.