1970 B51 Power Brakes

[R/T's 4 R/P]

Did Ebodies have a power drum option? I know 70 B bodies did.
Or, were all Power Brake cars front disc?
If they are front disc, isn't there a second proportioning block on the frame rail?
Is there a brake package or code difference?

[Skdmark]

I think this is all of the variants.

B62 10" drum
B62 + B51 10" drum w/power
B11 11" HD drum
B11 + B51 11" HD drum w/power
B41 + B51 Disc brake front, 10" drum rear w/power
B42 + B51 Disc brake front, 11" drum rear w/power (AAR and T/A)

Power drum was an option.
Disc brakes required the power brake option.

A32 and A34 axle packages included the B41+B51

Proportioning valve

[6bblgt]

the A36 3.55:1 "performance axle package" did NOT include power disc brakes

the two 4.10:1 DANA60 axle packages did: D32 & D34

[Skdmark]

the A36 3.55:1 "performance axle package" did NOT include power disc brakes

the two 4.10:1 DANA60 axle packages did: D32 & D34

You are correct.
Typo on my part.

[6bblgt]

 

[Dakota]

Did Ebodies have a power drum option? I know 70 B bodies did.
Or, were all Power Brake cars front disc?
If they are front disc, isn't there a second proportioning block on the frame rail?
Is there a brake package or code difference?

I have an A66 70 Challenger.   According to the e-bodies.org fender tag decoder output, the A66 package includes "heavy duty 11" drum brakes".   There was no specific brake call-out on the fender tag.   Best I can tell, the "heavy duty brakes" included a power brake booster and 11x3" shoes up front and 11x2-1/2" in the rear.

Regarding the second proportioning valve on the frame rail w/ disc brakes, the answer is "yes".  It's called the "rear hold off" valve.

https://www.rosevillemoparts.com/product/proportioning-valve-1967-71-mopar-a_b_e-body/

There are several explanations available on the internet for the purpose of the hold off valve (some of which directly conflict other versions - what a shock).   This version makes the most sense to me in terms of why the rear drum system needs a little head start on engaging ahead of the front discs:

https://www.freeasestudyguides.com/brake-metering-valve.html

[Skdmark]

@Dakota do you have B51 on your fender tag?

The HD 11" drums could be optioned to have power.
Power was not required with drums.

[R/T's 4 R/P]

Thanks...very helpful.
So, how would power (drum) brakes been ordered?  Seems in the dealer options that power brakes are connected with disc brakes.
Or, am i missing an option line?

Is the booster the same for drum and disc?
Then the master cylinder is the same as the one for drum brakes??

[JH27N0B]

The booster is same disc and drum.
Master cylinders are different drum v disc.  The drum MC is same power v manual except a dust boot is bolted to the flange, and you insert a push rod with a hard rubber retainer ring into the piston that gets locked in place in the piston.

[Dakota]

@Dakota do you have B51 on your fender tag?

The HD 11" drums could be optioned to have power.
Power was not required with drums.

I double checked my fender tag.   No B51 present.

My car has had a number of changes made by prior owners over it's life, so it's entirely possible that the booster was added after it left the factory.