Brake Booster/MC Replacement Q’s

[Moparfiend]

I have the wrong booster and possibly the wrong MC as well. I want to know what the correct MC to use for my 70 Sat with factory front KH disc up front and rear drums.

I know I need a duel diaphragm 8” Bendix Hex Booster.

What I have is a 1-5/64 or 1.075? Bore size MC with the gm style gold booster.

 

[PurpleBeeper]

I used this from Pirate Jack’s and have had good luck with it. My ‘70 came power front disc originally & I used this booster when the original one started leaking. I had to open up the firewall hole about 1mm (the Pirate Jack one has a slightly larger diameter than the original) and I think I added a reinforcement plate inside the passenger compartment. Figuring out exactly which master cylinder to use is confusing for a ‘70.

Bendix Style Mopar 1966-1970 B Body Power Brake Booster Conversion Kit BCK8536-1 OEM Style for 1966-70 Charger, GTX, Road Runner, Satellite

 

[Moparfiend]

I used this from Pirate Jack’s and have had good luck with it. My ‘70 came power front disc originally & I used this booster when the original one started leaking. I had to open up the firewall hole about 1mm (the Pirate Jack one has a slightly larger diameter than the original) and I think I added a reinforcement plate inside the passenger compartment. Figuring out exactly which master cylinder to use is confusing for a ‘70.

Bendix Style Mopar 1966-1970 B Body Power Brake Booster Conversion Kit BCK8536-1 OEM Style for 1966-70 Charger, GTX, Road Runner, Satellite

It’s a bit confusing as there are some MC that appear “deeper” than others but other than having a bit more fluid volume not sure it matters. It looks like the 1.125” bore is what I need from my digging. I think there is probably one maybe two manufacturers of the Bendix style booster and both are Chinese. So not sure it matters where I buy it. I DO see a $250 difference in pricing though….

 

[R/T Boy 67]

Buy the booster from Dr diff and use your existing master cyl, if it is working properly. The factory never used an 1.25" master cyl. for that application.

 

[Moparfiend]

Buy the booster from Dr diff and use your existing master cyl, if it is working properly. The factory never used an 1.25" master cyl. for that application.

Ok maybe I am not reading this correctly or maybe this information is not correct. This is from an article by Brad Schroder in Restoration Tech on Mopar Master Cylinders credit also Ram-man Wayne Brown. Here is shows that 70 bbody except 426 part number 2944477 1-1/8” bore for front disc set up. Am I reading this wrong?

 

[Moparfiend]

So I guess I’m answering my own question with the help of Wayne Brown. He is the most enthusiastic Mopar Brake guy I have seen. What he cleared up for me is the master cylinder port orientation for the bbody and the Hemi. It’s all clear to me now. The brake assembly I have seen by many is technically a Hemi orientation ie line ports facing away from the engine. The non-hemi face in towards the engine. All master cylinders appear to be deep well and have a 1.125 or 1-1/8 bore.

 

[R/T Boy 67]

The factory did use a 1.125"(not 1.25"), in certain applications, but if it was me, I would try the one you have, if it is working properly.I have always been a let's try this and see if it works, before spending money, kind of guy. You should do what you feel is right.

 

[Moparfiend]

The factory did use a 1.125"(not 1.25"), in certain applications, but if it was me, I would try the one you have, if it is working properly.I have always been a let's try this and see if it works, before spending money, kind of guy. You should do what you feel is right.

Thanks understood my mistake in typo. I corrected it. I get where you are coming from.

 

[PurpleBeeper]

It’s a bit confusing as there are some MC that appear “deeper” than others but other than having a bit more fluid volume not sure it matters. It looks like the 1.125” bore is what I need from my digging. I think there is probably one maybe two manufacturers of the Bendix style booster and both are Chinese. So not sure it matters where I buy it. I DO see a $250 difference in pricing though….

I’ve seen 3 different, power front disc brake, mater cylinders for 1970 Plymouth Road Runners. All 3 look about the same depth, but one is more narrow than the other two. The “wider” ones (2) are shown in the 1970 master cylinder video. As the video describes it, my car came with the wider “Hemi” master cylinder with the brake lines entering the master cylinder on the fender side (away from engine). My car had this master cylinder from the factory and also had a 383 engine from the factory (not a Hemi). The 2ns master cylinder is also wide & is listed in the video as the “non-Hemi” with brake lines in the engine side. The 3rd type I’ve seen is narrower than the other two & has brake lines also on the engine side