Old GM B body interchangeability

A friend of mine picked up a new toy. A 61 Buick LeSabre 4dr hardtop. It is pretty rad. I got the old nailhead running pretty well and attempted the maiden voyage and found the master cylinder seized. To add insult to injury it is rusted to the rod in the booster pretty well, too.

I haven't fought the master completely off so I have yet to measure the bore.

I am hoping there might be some sort of general GM interchange option. I would love to find a different booster/master combo that would drop in place. Preferably a dual circuit piece. We have struck out looking for a replacement and sending this one off to be sleeved and rebored isn't in his budget.

Is this GM B platform car totally different from the legendary later cars?

Resuscitating the beast

Not sure it'll help you but on my old 60 Cadillac A body I put in a 67 Cadillac booster and dual circuit master cylinder. Just had to elongate two of the holes.

The master in question

Very little interchange between GM brands back then. They used totally different engines, drivetrains and chassis. I don't know about the brake and booster, but it doesn't look at all like the one Pontiac used in 1961.

The one thing they did have in common was window glass.

GM used single circuit til 66, went dual in 67. I'd bet if you looked at stuff from about 1970, you will find they are readily available in the aftermarket, and will not look out of place in a classic. I also think that it won't be an unreasonable job to mount the entire booster/master/prop valve assembly from the donor car.

Do you have a classic car wrecker anywhere near you?

find an internet forum dedicated to those cars and find out how people have upgraded them to modern brakes.

a quick google search confirmed my suspicion that a master cylinder out of something newer bolts right up, with only the length of the pushrod from the pedal needing to be changed. a few of the links said 1970ish Monte Carlo/Chevelle master cylinder..

Be careful if you get up into the 70s about the switch to disc brakes on the front. That's why I went with 67 stuff cause it was still drum/drum so the MC worked. Plus Auto Zone had that year on sale.

Stampie wrote: Be careful if you get up into the 70s about the switch to disc brakes on the front. That's why I went with 67 stuff cause it was still drum/drum so the MC worked. Plus Auto Zone had that year on sale.

Truth.

I want to say you need the booster off a late 60s something or other too, I think that 4 bolt master flange pattern is exclusive to the single circuit brakes, at least from the factory. The firewall bolt pattern is likely common. I'd go the junkyard and look for medium and big 67+ GM cars, you might get lucky. Once you have a booster that fits and has that 2 bolt master pattern it should be easy to find a suitable master, so don't worry much about it having front drums.

I can tell you the MC is 1" bore, or so claim the rock auto rebuild kits.

Alternatively, you can keep it single circuit and make sure the parking brake is in realllllllllllly good shape.

You'll get lucky and find something. 60-64 were some of the last years before a large consolidation. My 66 Bonneville has some cast-off suspension bits from my 96 Impala SS.

The only thing I can think of that might be a hitch in the works is the booster bolt pattern. If that is the same, the sky is the limit. My 67 LeMans now has an S10-style booster with a B-body style master.

The A-bodies (in general) used a bracket that pushed the booster forward and up. The bracket used a four-hole pattern on the firewall side that is less-than-square. Take a look at this pic:

The holes marked with "1.7" are the firewall side. This was common for the intermediates; A, G, F, Y, S bodies. The other side marked with "3.375" is the booster side. What they did for B and D bodies was eliminate the bracket and bolt the booster directly to the firewall.

So, the bolt pattern (4 holes on the firewall) were spaced 3.375" for B and D bodies, while the intermediates used the 1.7" spacing. Measure the spacing from inside the firewall. If it matches either of those, you can use nearly any GM booster which will allow you to use nearly any GM master.

Here is what I did for the LeMans:

Take note that it includes the brackets to go from the 3.375" booster pattern down to the 1.7" pattern of the LeMans firewall. It also includes the adjustable pushrod. This kit would technically work in a B or D body if you just skipped the brackets.

The other thing to consider is the prop valve. If you are keeping drum/drum, you don't technically need one, but it is nice to have to fine tune.

Those kits are $150 on ebay and basically include everything between the pedal and brake lines.

So, if your bolt pattern is one of those two, upgrades are easy. If they aren't, bust out the drill and you're golden.