Boss wants to order a disc brake kit, but what size brake booster, '67 Barracuda w/273 auto?

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ProjectBazza

ProjectBazza

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My boss purchased a (really clean!) '67 Barracuda last year, and now he wants to put a "disc brake kit" (his words) in it. (Edit: Car is currently drum brakes all the way around, and this "disc kit" is for the front brakes only.) He says he's found a "kit" somewhere, but he's confused as to what size brake booster to order, as he's found them in 7", 8", and even 9" in diameter. We both assume the differences are due to brake sizes (caliper and wheel cylinder bores), and I told him to reach out to his kit provider for their input, but he asked me to post this question here as well.

Anyone know what size brake booster would have come stock on a '67 Barracuda, 273, auto, w/disc brakes?

Pictures below are of his car as it sits right now (well, when he bought it last summer, that is).

Any input and/or advice would be greatly appreciated, and thanks, all!

Jim

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What "Kit" is he planning on using? manufacturer/ reseller/ part number.
there are typically a few ways to go with front disk. OEM (67-72 would be 4 piston fixed, Kelsey Hayes, front disk with 10x1.75 rear drum this retains the SBP 5x4" lug studs) OEM replacement (73 up single piston, sliding caliper, front disk with 10" rear drum, this also gets you 5x4.5 BBP lug studs) and various aftermarket "Kits" that may uses either of the above parts OR custom calipers from who knows what application.


Either of the OEM setups can be done with OEM parts, If the car has 10" front drums there are kits that use an adapter bracket to mount the calipers to the spindles or come with replacement spindles that are OEM or OEM replacements.

As for power brakes it's really not needed and can be added after the disk are installed if so desired. (That's the route I would go, "The parts you don't add, don't cause you no trouble")

Go to MYMOPAR.COM and download the 68 Plymouth or Dodge Factory Service Manual and the 68 Mopar Parts book (free PDF)

Also search here for info, there have been a million posts about good and bad front wheel disk swaps.


Advice... if you can find a donor car or a complete setup you will be in a better place as it will have examples of the nuts and bolts and how it all goes together
 
Actually, I don't think the size of the booster is necessarily related to the brake size. It was more related to the engine compartment clearances of different models and which supplier had the contract. Of course, one size is "correct" for OEM installation on 67-69 A-bodies, but it's not like the others wouldn't work with the correct pushrod, etc.

That said, I agree with Dana that a booster is not needed. But consider the 15/16" bore disc brake master cylinder. A larger MC bore will create a stiffer pedal that some people find objectionable. Options are 1", 1-1/32" and 1-1/8". I have 1-1/32" and that is a very hard pedal. I used 15/16 on my other car and it seemed perfect.

Oddly, power brakes used the 15/16" bore, because the booster needed the mechanical advantage.
 
mvh said:
Oddly, power brakes used the 15/16" bore, because the booster needed the mechanical advantage.
Click to expand...
That depends on the year


67 - 70 - 1" manual or power for A bodies w/disk or drum

71-72 Disk and drum Power or manual changed to 1-1/32


67
1780945756768.png


69
1780945917189.png


70-71 (dart and Valiant only as Barracuda was E body then)

1780946128729.png
 
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ProjectBazza said:
My boss purchased a (really clean!) '67 Barracuda last year, and now he wants to put a "disc brake kit" (his words) in it. (Edit: Car is currently drum brakes all the way around, and this "disc kit" is for the front brakes only.) He says he's found a "kit" somewhere, but he's confused as to what size brake booster to order, as he's found them in 7", 8", and even 9" in diameter. We both assume the differences are due to brake sizes (caliper and wheel cylinder bores), and I told him to reach out to his kit provider for their input, but he asked me to post this question here as well.

Anyone know what size brake booster would have come stock on a '67 Barracuda, 273, auto, w/disc brakes?

Pictures below are of his car as it sits right now (well, when he bought it last summer, that is).

Any input and/or advice would be greatly appreciated, and thanks, all!

Jim

View attachment 1716553148

View attachment 1716553149

View attachment 1716553150

View attachment 1716553151
Click to expand...
He needs to talk to Cass at doctordiff.com
End of story.
 
Let the Boss know he can get a copy of the IBM card for his 67 it has many of the codes from the build sheet

see post #1 for info

Dana67Dart

Thread 'Chrysler Historical new contact info.'

They are now Stellantis Historical Archives.

Danielle Szostak appears to be the go to person.

Her email address is Danielle.Szostak@Stellantis.com

This is the text of the email I sent to her in Feb of 2022

"Are you still fulfilling requests for vehicle specific data that Chrysler Historical once provided?"

This is the text from her e-mail to me:
"Thank you for contacting the Stellantis Historical Archives. At this time, we would like to thank you for being patient with us while we work through our backlog of requests with a limited staff and partial office hours.

To...
 
This is how the Boss' car decodes...

Looks like its a Formula S with HP 273 NICE!!! AND its a convertible even NICER let him know he is officially one of the COOL KIDS!
1780956428043.png
 

I'm not trying to tell you what to buy. And if I'm wrong for posting the pic please remove it moderators. But on my 66 Dart. Had 9" drums on front. Installed RPUI The right stuff disc brake conversion. $1500 manual brake kit. It doesn't take much pedal effort and it Stops gggggreat. Uses standard single piston 72-76 A body brake parts. Oh also bought a harbor freight vacuum brake bleeder for a 1 man job. It's a 1 day job.

MDC66SD-P-0__95456.jpg
 
I used PIRATE JACK'S for my 68 Fasback non-power front disc . They supplied ALL parts including 4" bolt pattern drilled and slotted rotors. The kit even includes new disc brake spindles (I didn't want to convert drum brake spindles to disc ) The kit fit and worked perfectly. 3 owners later the brakes are still working without issue. They even paid the freight and the kit is pretty heavy. I think if I remember it was around $700 shipped ?
 
Thanks, everyone!

Boss Man has been gone all morning, but when he got in, before I could walk over there and talk with him about the responses you all posted, he poked his head in my office and said he's had a change of heart. Despite me trying to gently push him away from doing this, he's going to leave the car as-is (drum brakes), and just add the brake booster (7" diameter, w/new master, I assume), for two main reasons: 1) Downtime (he can't get the guy who going to do the work commit to a schedule), and 2) He's going to be handing the car down to his wife and daughters eventually, and apparently none of them are comfortable driving it with "manual brakes" (their words).

My apologies for (somewhat) jumping the gun on this, but I posted the question with honest intentions.

Thanks again!

Jim
 
ProjectBazza said:
He's going to be handing the car down to his wife and daughters eventually, and apparently none of them are comfortable driving it with "manual brakes" (their words).
Click to expand...
Both my daughters have / can drive my 67 Dart, manual steering and manual brakes with oem front disk.

no issues
 
Dana67Dart said:
Both my daughters have / can drive my 67 Dart, manual steering and manual brakes with oem front disk.

no issues
Click to expand...
I don't disagree, but when it comes to our wives my boss is a lot like me, and learned these two words long ago:

"Yes, dear!"

:lol:
 
I personally like all the luxury stuff, power steering, power brakes and ac. Heck, give me a cruise control too! My Barracuda has all of those. But I am an old man who drives like an old lady…..

One thing to keep in mind; the smaller the booster, the higher vacuum it takes to operate it. Small boosters are often trouble with low vacuum engines.
 
Have them try it as is. Manual drums is a different world than manual front disks. The drum system used on these cars uses leverage to amplify the hydrualic forces. Its not like driving a Model T or even a 1940s Dodge. With good linings and everything set up right, those 10" drums are decent.

The downsides of the self-energizing action are:
Easier to lock up one or more wheels (booster won't help with that).
When friction goes down then there is less to leverage. (such as wet from driving through a stream or lining got too hot).
 
I was at a car show, a fastback cuda had a small block,headers,PS,AC,PB. No thanks only because I work on cars everyday for a living. I don't like working on my 66. But I respect guys doing this to their toys.
 
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