oldsman330

i have a 66 olds f85....single res master....where can i find a dual res master to upgrade my brakes.....i have a power brake all drum system...

Run to Rund

John Andreotti at Ott's Friction Supply has supplied such dual master cylinders to me, the Centric brand looks almost exactly like the original used in 1967. You will need to scrounge up the cup shaped pushrod retainer used on A bodies with manual brakes from 67-72. He has also been my "one stop shop" for all brake parts for my Oldsmobiles.
John Andreotti <andreotti@ottsfrictionsupply.com>

oldsman330

thanks..dropping him a line now......question...whats the manual cup for as i have power drum brakes not manual?

joe_padavano

Note that you can get the Centric M/C from RockAuto. Personally I'd use a brand name like Wagner or Raybestos. You don't need the manual cup. You DO need either a 1967 power booster or you need to modify the pushrod between the booster and the M/C on your current power booster. The dual M/C requires a much shorter pushrod.

Run to Rund

My Centric cylinder has worked fine for 4.5 years now, and Ott's has had good luck with them overall.

I beg to differ with Joe on needing the cup retainer (actually more like a derby or bowler hat). Three NHRA stock racers have destroyed their cars and been seriously injured recently (Ken Etter is one) because the pushrod came out of the master cylinder. For example, if you are hard on the brakes and then sidestep the pedal, the pedal and pushrod can come back immediately while the piston in the master cylinder has to suck fluid to come back and may be delayed. The 66 manual cylinder uses a plate and snap ring to retain the pushrod by its flange head. In 67-72, without the bowler hat retainer, there is NOTHING to retain the pushrod positively. That is why GM used this retainer on ALL manual brake A bodies from 67-72.

The pushrod length to the stock clevis at the pedal arm will be about 4.12" with manual brakes.

I'm trying to find a current supplier for the retainer; AC Delco 179-1247 brake pedal pushrod retainer might be it; I have ordered one to check, as I couldn't find a photo on-line.

joe_padavano

Joe,

I agree with you completely about the retainer on a manual brake car, but from the O.P.:

There is no retainer, just the rubber seal at the M/C to power booster interface.

oldsman330

well like i said before...its a power brake all wheel drum brake system.....sooooooooooooo.......thanks for the heads up.......as im going to the englishtown swap meet this weekend...is there anything in dual res master cylinders to look for?? id love to come home with one and install it this sunday....what make and year dual master should i be looking for...otherwise..ill get the one from the guy at the beginning of this post.......as far as the rod...i can shorten it with no problem myself....been there done that...

Run to Rund

Oops, sorry, I didn't catch the power brake part. I thought he was converting to dual master cylinder manual brakes. I don't know if the same booster can be used with either cylinder; I suspect the pushrod inside the booster to the master cylinder will be different, though.
I am used to hearing from the guys who are running big cams and want manual brakes these days. . .

Don't forget the lines route differently. On a 66 single master, the output line goes to a 4-port distribution block that the two front and single rear line also connect to. On the 67, the rear line goes up to the master cylinder' rear port (closest to the firewall), and there needs to be a T going from the front output line to the two front lines.

oldsman330

ahhhhhhhhhhhhhh yes.....thanks run

joe_padavano

That is correct, as noted earlier in this thread. You can either use a 67 booster or cut down the pushrod on the 66 booster.