Retrofitting a master cylinder.

[celticwarlock]

Has anybody retrofitted a master cylinder from a different application onto a C-body? I think I remember somebody using one from a later cargo van or similar vehicle.

Mine works fine (it's an older re-manufactured unit that the car came with) and I don't intend to do anything with it soon, but I will be doing other brake work in the near future, and I'm considering replacing it. The car in question is a 1969 New Yorker with factory front disc brakes.

I remember having cars from the 70's when I was younger (back in the early 90's), and having master cylinders fail on me suddenly, which can be a harrowing experience. I am told that more modern master cylinders use more piston seals than older ones did, making them less prone to sudden failure. I figured this might be true, because I have not replaced a single master cylinder on any vehicle that I owned since then, and I've owned literally tens of vehicles, many with over 300,000 miles on them.

I have had the car for 16 years, and if there is a more modern master cylinder from a different vehicle that would fit my application, I would strongly consider using it.

 

[Big_John]

The things that kill the seals are pretty simple.

Age and ridges in the bore.

Age is simple... Rubber isn't like fine wine and I don't care what MC it is, old rubber is not good rubber. Beware the "NOS" offerings with old rubber.

Ridges can be from wear or from sludge build up in the bore. It never bothers you until something happens like you bleed the brakes and pass the rubber seals over the ridges and they ruin the seal.

So, the answer is just new seals in a good bore.

The new cars last a while because you are using them regularly. Simple as that.

IMHO, you aren't getting better than what's already on the car. The new pieces are often used because they are lighter or smaller. Not something you are probably concerned with. You have a MC with a large reservoir, and that's a plus. You may not have that with a modern piece.

 

[Davea Lux]

You have large diameter caliper pistons on you '69. This means you also need a large capacity disc brake master cylinder to accommodate for wear on the disc pads as the caliper pistons move further out to compensate. There are still new master cylinders for your vehicle available, so I would suggest staying with a stock type unit.

Dave

 

[fury fan]

A big problem will be getting a modern MC in 4-bolt style to fit your booster. (FWIW, I am using a mid-70s Dodge truck MDisk master cyl on my car, but I have manual disks).

You could swap to a 79-newer booster (I believe those are 2-bolt), to get more MC options, but you'd have no way to know if you were getting enough boost for maximum braking. Unless you compare the diameter of that type of booster to a '71-74 unit - that might give you a fair ballpark comparison. But that would also be assuming that a '71-74 single-diaphragm gives equivalent boost to your '68-70-style dual-diaphragm.

There are 2-4-bolt MC adapters available, but those might require fiddling to get proper pushrod insertion into the MC. And when changing boosters between car lines, or that have different pedal brackets, there is always the risk you'll need a pushrod adapter to mate the booster to your pedal.

You have large diameter caliper pistons on you '69. This means you also need a large capacity disc brake master cylinder to accommodate for wear on the disc pads as the caliper pistons move further out to compensate. There are still new master cylinders for your vehicle available, so I would suggest staying with a stock type unit.
Dave

Actually, I believe the 74-78 pistons are larger dia (presumably same bore length) and the GM calipers that are popular in the aftermarket conversion kits claim to be larger also. So there might be some GM MC that might retrofit as it would have higher volume.

IMO, if we need to change hte MC every 5-ish years that's actually good preventive maintenance - it gets you a new fluid flush thru everything.
And you might spend more time trying to adapt something that might end up not working as well as you hoped it would.

 

[celticwarlock]

Outstanding information.

This is why I consult the C-body Brain Trust before making decisions that could complicate things for me. In light of everything I've just read, I think I'll opt for a new Raybestos unit. At least I know it will fit right away and will be a reliable replacement for the current one.

 

[69PHOENIX]

G'Day Fellas,
Just Curious, I've Seen a Few Discussions of This Type But Not the Solution We've Been Using for Years over here.
Anytime We Have This Sort of Problem We Get the Original M/Cyl Re-sleeved with Stainless Steel. (Wheel Cyls Also)
Never had a Problem, Never had One Wear Out Once Done.
Is There a Reason That You Fellas Don't Do This?
Regards Tony.M

 

[70bigblockdodge]

Late 80s into the 90s aluminum master cylinder from a pickup truck or van will work. You need a adapter 4 bolt to 2 bolt and you may need to add something to pushrod to compensate for adapter. Only buy new aluminum master cylinders, it's hard enough to get a good cast iron reman let alone aluminum. There is no advantage other than weight, which on a power brake C body is about nill.

 

[Big_John]

G'Day Fellas,
Just Curious, I've Seen a Few Discussions of This Type But Not the Solution We've Been Using for Years over here.
Anytime We Have This Sort of Problem We Get the Original M/Cyl Re-sleeved with Stainless Steel. (Wheel Cyls Also)
Never had a Problem, Never had One Wear Out Once Done.
Is There a Reason That You Fellas Don't Do This?
Regards Tony.M

Cheaper to buy a new one. Simple as that.

 

[69PHOENIX]

Big_John,
Fair Enough, But Then I Seem to See Regular Complaints about the Cheap & Nasty Components Now Available.
At Least with Stainless the Job is DONE.
Plus No need to Adapt / Adjust / Modify.
Got Club members Who Had their M/Cyl done 30 Years Ago No Problems Since.
Just My Opinion.
Tony.M











-

 

[Big_John]

Big_John,
Fair Enough, But Then I Seem to See Regular Complaints about the Cheap & Nasty Components Now Available.
At Least with Stainless the Job is DONE.
Plus No need to Adapt / Adjust / Modify.
Got Club members Who Had their M/Cyl done 30 Years Ago No Problems Since.
Just My Opinion.
Tony.M
-

I do agree that it would be the way to do it right. There are a few places doing that type of work, but it's mostly done on master cylinders that aren't readily available.

It's economics though... The only prices I could find was to sleeve with brass for $145. I would expect SS to be a bit more, but let's just say $150. That doesn't include anything else, so now we have to source a rebuild kit with new rubber... and that might be a little tough to find, but let's say $20. Add some shipping and you are easily over $200. I can buy a new Raybestos MC for my car for $50. Granted, that's probably an offshore built piece, but it's a quarter of the price. Not a lot of guys are going to want to fork over the cash or wait weeks for their MC to be sleeved either. I realize that the economics of labor v. parts cost is probably much different where you are importing the parts, so it may make perfect sense to sleeve/repair what you have.

Years ago, I used to rebuild brake cylinders and have even done a master cylinder here and there. They became throwaway items somewhere along the line when it became cheaper to replace than rebuild. I've gone back to rebuilding brake cylinders, even sourcing older NOS or NORS pieces if mine weren't rebuildable and replacing the old rubber to give me the best bang for the buck. So, quite frankly, IMHO, having the old MC sleeved is a better and quite possibly more economical repair than buying some over hyped/over priced NOS piece that may have sat on a shelf for 50 years with 50 year old rubber. The next MC I do may be done that way, but we'll see.

 

[USSMOPAR]

 

[C-440-300]

Outstanding information.

This is why I consult the C-body Brain Trust before making decisions that could complicate things for me. In light of everything I've just read, I think I'll opt for a new Raybestos unit. At least I know it will fit right away and will be a reliable replacement for the current one.

Oh Master War Lock, Pray tell this minion the model number(s) of your cache? Thank you!

 

[Boydsdodge]

On some of the performance Mopars I have used the aluminum two bolt masters with adaptor to booster or no booster. The later 2 bolt master cylinders are what I would call a male base so the adapter does not cause an issue with push rod. You will need to check for proper adjustment of pushrod like you should do with any master swap. Richard Ehrenburg was selling aluminum master kits with adaptors.

 

[C-440-300]

On some of the performance Mopars I have used the aluminum two bolt masters with adaptor to booster or no booster. The later 2 bolt master cylinders are what I would call a male base so the adapter does not cause an issue with push rod. You will need to check for proper adjustment of pushrod like you should do with any master swap. Richard Ehrenburg was selling aluminum master kits with adaptors.
View attachment 600953

Thank you, Boydsdodge.. E-Booger, eh? Ebayer still? I'll check.

 

[Boydsdodge]

Security Measure

www.ebay.com

Mancini Racing

Master Cylinder Adapter

Watch what bore size you are buying.