Late model power brake booster upgrade

[Myself]

I just finished this up and thought I'd share what I've learned. The brakes were not working on this truck and the owner said "Do whatever you want, just make them work." I was heading to the junkyard anyway to get some other parts, so I was on the lookout for a brake setup. This particular unit is a dual diaphram booster from an '89 Chevy 3/4 ton van. The whole thing was $35. It bolts straight to the firewall, instead of a bracket like the original. This truck had already been changed to a ''75 ish setup at some point in time. Here are both of them.


I decided the first step would be to remove the bracket from the old booster. I just had to grind through the rivets,


and pop the brackets loose.


The '75ish brackets were a little bulky for my tastes, so some trimming was in order.


The long studs on the newer booster also need trimmed. About 1/2 way will do.

[Myself]

If the studs aren't trimmed they will interfere with the mounting studs on the firewall.


With that stuff done I figured I'd work on the brake push rod. The old one pulled right out of the booster. Let's just say the newer one didn't go so well. Here are the two for comparison.

And here is what happened while I was rough housing the other one to get it loose.


So guess what!??! Time to learn about brake boosters. Here is the original plane jane booster.


And here are the guts of a dual diaphram unit.

[crakarjax]

So basically you are saying "don't try this at home"?

[Myself]

So after dis-assembling a third Firebird setup I had around. I was back in business. I now recommend just wrapping a wet rag around the base of the rod, and welding it in place. From the back of the booster bracket (where it mounts to the firewall) to the hole center on the push rod, I ended up with about 8 1/2".


Once I got it mounted I didn't like the way it looked kind of slanted toward the firewall. I found a couple of 1/8" shims behind each top stud were just right. To make it a little more incognito later I'll stack a few washers back there. Now the only thing left to do was bend up some new short lines to the proportioning valve. The front and rear outlets on the '89 master cylinder are backwards from the old cylinder. Rear to front, and front to rear. The lines I used were 12" long. After a bleeding session all is working well. And to push the pedal is almost effortless.






I hope this helps some of you folks

[crakarjax]

Are there any late model booster/MCs that bolt right up?

[Myself]

Everything late model that I saw bolts right to the firewall. But the bolt spacing is just right for the old style bracket. It fit right on without modding any holes. Did I also mention this saved about 8#'s?

[ChevyAndi]

Hi,

im glad that i found your post!

I have a 71 pickup, an im parting a 90 G20, i was thinking to use the booster/cylinder on my pickup. Now i know it runs!

Have you disc/drum too?

What size of adapters do i need at the brake lines?

Runs great with that combination?

Greetings

[Myself]

Yes, the truck is disc/drum.
Not sure on the adapters, nothing was labeled at the parts store. Everything just said "3/16 brake line adapter". We just pilfered through them until we found the ones that fit.

The setup works great!

[crakarjax]

Originally Posted by Myself

Everything late model that I saw bolts right to the firewall. But the bolt spacing is just right for the old style bracket. It fit right on without modding any holes. Did I also mention this saved about 8#'s?

But you just went through all the mods you had to do to get this thing to fit... doesn't sound like it bolts up there. I'm talking a straight up swap, no welding necessary bolts up. Any of that out there?

[Myself]

Not later model, no.

[Andy4639]

If you have the brake booster already can the master cyclinder be used for the old booster? it looks like it bolts up the same as the older style...Just saying.

[Myself]

No, the bore sizes of the master cylinders are different.