How to identify B-Body (or E-Body) firewall mounting plates | 1962-1974 | manual vs. power

cudak888

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***Repost of 2016 thread w/photos restored***

Last night, I wound up doing a few forum searches, trying to figure out if I needed to change my firewall bracket for my disc brake (non-power) conversion (I was also inspired to do so after reading this thread).

After sorting through all the info I found, I realized that the firewall plate variants are really quite easy to understand - provided all the information is in one place, separated by year. But it isn't...so #newthread.

I compiled everything I could find and assembled the following chart below. For the sake of identification, I copied a few photos that I found here that demonstrate the differences, and credited the sources (hope you fellows don't mind), as I'm not lucky enough to own every single plate made.

Would also be glad to edit and update this as more information comes out. One of the things that I can't find yet is a photo of the bellcrank on a power brake-equipped '65 (which I'd assume are rather unusual to begin with).

1962-1965 B-Body:

Manual booster at left, power booster at right. Power booster requires bellcrank. Not reproduced. | Photo: moparmarks:

62-65-manual-left-power-right_original_moparmarks.jpg


1966-1970 B-Body:


NOTE: 426 HEMI applications use manual master cylinder firewall plates and a much larger bellcrank that's built into the booster standoff (photos of this complete assembly shown in last section below).

Booster bracket for cars with manual master cylinders OR power brake HEMI 426 applications. Original shown. Not reproduced. | Photo: challengersteve

66-70-Manual-Power426-bracket_original_challengersteve.jpg


Power booster bracket for all applications excluding 426 HEMI.
Requires standard power booster bell crank without booster standoff.
Original, shown from reverse side Photo: 69bee:

66-70-PowerSTD-bracket_original_69bee.jpg

  • Reproductions of '66-70 power booster brackets (the same thing above):
  • Version #1, shown with bellcrank:
66-70-PowerSTD-bracket_repro1.jpg


  • Version #2, shown with bellcrank. Only apparent difference are the two extra holes. NOTE that I suspect this might be a vendor's Photoshop of a manual booster plate with the holes moved around, and that the only one you can actually get is the first version. Either way, it'll make no difference in operation:
66-70-PowerSTD-bracket_repro2.jpg



1971-1974 B-Body + 1970-1974 E-body:

Booster bracket for cars with manual master cylinders OR power brake HEMI 426 applications.
Original | Photo: moparmarks:
71-74-manual_original_moparmarks.jpg


Reproduction by Dr. Diff | Photo - Dr. Diff :
71-74-manual_repro_drdiff.jpg


Power booster bracket for all applications excluding HEMI 426. Requires bell crank for proper operation.
Original | Photo: eBay, wolf-pack68
71-74-power_original_wolf-pack68.jpg


Reproduction (shown from the rear, rotated 90 degrees) | NOTE: Some sites show a stock image of this part, but show it six holes that don't appear to line up with the original. These places have Photoshopped the '66-70 power bracket to look like this.
71-74-power_repro.jpg


Pedal rods, bellcranks, and other things you should see to know - 1962-74(ish):

Manual brake rod:
Manual brake booster rod shown on a 1968 B-Body:
68-manual-brake-rod.jpg


Power booster w/bellcrank for 1966+ applications, bellcrank pivots from bottom. Note: I believe 1965 is inverted and pivots from the top, but have not found a photo of one | Photo: moparmarks:

68-bellcrank_moparmarks.jpg


HEMI 426 (factory Gen II) booster (Note manual brake plate mount and built-in bellcrank. Offset plate and oversized bellcrank currently reproduced). | Photo: Chattacuda:
hemi-booster-chattacuda-1.jpg


hemi-booster-chattacuda-2.jpg


hemi-booster-chattacuda-3.jpg


That's it - six plates with eight unique factory applications, spread over three generations of B-bodies. Not really that complicated.

-Kurt
 
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cudak888

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Someone DM'ed me about where you can get the Hemi offset bracket.

There's a cad-plated Gen II Hemi bracket only that makes the rounds as a "1965-1970 Mopar Brake Booster Bracket." They're usually sold as a "power brake conversion bracket" for A/B/E Bodies. Part of that marketing makes me think they're taking advantage of people that don't read this thread and aren't aware of the proper bellcrank for B/E bodies without Hemis, but that's another story.

Either way, they're on eBay and other places. Play around with the search keywords "Mopar Brake Booster Linkage" and you'll probably find them eventually. Here's a link to an overpriced one ($98 - the same bracket is listed new on eBay for $58), on Speedway Motors - though the link will probably be dead in a year or two if they modify their website; seems to be the case with most links I find in older threads:
https://www.speedwaymotors.com/1965...5o6OGhCfTHIcTypV7eVkjKhfCjbumnQBoCs8MQAvD_BwE

91031989_L_13109e85-567f-4762-a58f-c02d960eb316.jpg


Dr. Diff sells a different reproduction with the booster. This one is painted black and isn't from the same tooling. You'll find it a $225 option in the menu.
https://www.doctordiff.com/bendix-style-dual-diaphragm-booster.html

back-hemi-booster.jpg


This said, I wouldn't fault anyone for installing one of these offset brackets on a daily driver with an LA or RB, and I'd recommend it if your build prioritizes maintenance over originality. The Hemi bracket makes servicing massively easier if you have to pull the booster, as the nuts are relatively accessible. Ditto for the master cylinder - no more unbolting it from under the dash and around the pedal box.

<rant mode on>

There's a very good reason I recommend the Hemi bracket for servicing: Removing a firewall-mounted booster from a fully-assembled '66-70 B-Body is a job invented in the fieriest depths of hell, and I sincerely hope the engineer who came up with the design is there now - and is being used as a voodoo doll.

It's one of those things where I'm still utterly mystified why Chrysler engineers were so intelligent with the A-bodies (knurled studs from the firewall out) and so stupid with the B-bodies (knurled studs on the master leading to one nearly inaccessible hole, and one totally inaccessible hole). This repeats itself all over the dashboard areas of these cars - A-body is an intelligent joy, B-body is a maddening mess. Doesn't make sense.

</rant>

-Kurt
 

snakeoil24

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Kurt so im still a little unclear untill i lookat more brackets. But your help is priceless. My next project is ac box. I want to find a motor that is real short so i can put the traditional air ac box in the car with a short blower motor so hemi valve cover wont hit the blower motr any idea where to find?? I have the bracket btw for hemi booster but im hoping the off set one your talkin about is considerably more off set
 

cudak888

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I have the bracket btw for hemi booster but im hoping the off set one your talkin about is considerably more off set

There should be only one HEMI-style bracket - they probably all follow the same specs, and thus are offset vertically the same amount. If they didn't, there would be linkage ratio differences.

Perhaps there are alternates, but I haven't tinkered with any of them to find out. I've only played with the standard bellcrank and booster repops.

Funny enough, and after having my repop booster leak and endless master cylinder issues (upper cover leaks + surface rust + fluid leaks), I lost patience and went straight back to manual disc/drums, installed the two-bolt master adapter plate, and fitted a modern aluminum master. Archaic, but it simplified the system, and it still feels good. It also made it a cinch to pressure bleed the system (which, in my case, was a necessity due to trapped air that was proving an impossibility to purge via conventional pedal bleeding).

-Kurt
 
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