brake booster and master cylinder mounting problems.

[71LS5Formula]

I have a 71 Formula. It has a brake booster from a 79 4 wheel disc trans am. I got a wilwood master cylinder and cannot get it to sit in place properly. The problem I'm seeing is the sleeve and pushrod from the booster are keeping it from sitting. Are there any adapters to help correct this? Thanks.

[Apogee]

First, which Wilwood master cylinder are you using with the '79 T/A dual-9" booster? Is it the #260-8556 unit with a 1-1/8" bore? The right picture showing the issue in this instance could be very helpful.

Tobin
KORE3

[71LS5Formula]

It is the 260-8556.

[71LS5Formula]

[Apogee]

Thanks for the pics. The pilot register on the Wilwood 260-8556 1-1/8" bore master cylinder extends .600" from the mounting flange, and the flat of the MC piston is about .168" shy of that. The Wilwood dimensions are consistent with most GM short pushrod master cylinder specifications with the pushrod spacer installed, so I'm not sure what the fitment issue is with your components. Maybe someone more versed in the 79-81 dual-diaphragm F-body boosters will chime in.

[Skip Fix]

I want to think the one I put on my 78 back in '82 had no pushrod and the factory one for it was adjustable. But been a few years. I think I have an extra factory 81 MC somewhere I can measure if you need me too. The 79-80 booster had a smaller register for the MC than the 81 as the 81 used a aluminum Quick Take Up for the Low Drag front calipers and 79=80 used a cast iron with a smaller register. Be sure the OD on the Wilwood is not hitting inside the booster if it is a 79.

[71LS5Formula]

Sorry. I think I'm leaving out something. The sleeve and rod in the booster are the problem.

[Skip Fix]

Sleeve in the MC recess? I know some MC(Summit 1" Vette copies) have a removable sleeve to take up the hole depth for manual or booster As I said some of the factory boosters had a removable adjustable rod-not sure if your is. If it is it slides out. Granted an iron MC is kind of ugly but you might pick up a cheap rebuilt one just to check if it actually fits the booster(then a booster issue) and to compare dimensions to possibly modify your Wilwood to match the depth.

[rohrt]

That booster is an odd one to me. I have a handfull of 79 9" boosters around the farm. That one looks more like my 9" booster from my 64 Tempest. The 79 boosters I have seen are fatter and longer but maybe it just the pic angle in your post. The 64-67 booster had a sleeve like that that would come out with the pushrod. What is odd it the pushrod/sleeve look to long for the shallow pocket MC and not long enough for a deep pocket MC.

I have been dealing with a lot of brake issues with my two cars this year. I bought one of the Master power brake tool to measure the depth of the pin and I have say I have used it a lot now.

Here was my 9" booster with the long pushrod




This is with the short pin ready for a dual master conversion



Here is my 68 bird using the Master Power break check tool





Here is the 79 booster left next to my 64 booster on the right.

[71LS5Formula]

Rohrt.
It is a 79 4 wheel disc booster. That one with the short sleeve and rod in the 2nd pic would probably fix my problem. What are they from?

[Hydratech®]

Is your brake pedal connected to the brake booster? If so, disconnect the pedal and see if the pushrod on the master cylinder side relaxes inward. I'm thinking you either have preload of the brake pedal rod under the dash (caused by brake light switch adjustment or rubber pedal stop) OR your vacuum booster is defective. The MC pushrod and the plastic sleeve should not be protruding outward like that.

"I got twenty bucks says your problem is under the dash"

[71LS5Formula]

Pedal is not attached.

[Hydratech®]

Get a replacement booster - the one you are dealing with is defective (looks like a freshly installed Cardone reman in your images). The MC pushrod definitely should not be sticking out like that. It is not a matter of your choice of booster, meaning get the exact same part number / application you currently have...

Or? Maybe consider one of ours?


http://www.hydratechbraking.com/GM_2ndgenF_Body.html

[71LS5Formula]

I'm gonna look into seeing if there is an adjustment that I'm missing. I've thought of hydra boost in the past, but haven't gone any further than that. Might look into it later.

[71LS5Formula]

Figured out the problem. The Black tube that goes through the firewall is grabbing the top of the adapter plate. I'll be filling the opening to make it clear.

[71LS5Formula]

Fixed. The hydraulic clutch master cylinder bracket was interfering with the booster. All good now.

[Hydratech®]

Well, so the problem turned out to be in the dash / firewall instead of under the dash (with brake pedal related issues). Does this mean I was 1/2 right?

At any rate, I'm glad to see that you have discovered the real issue at work here, and did not attempt to bandage the first knee jerk response by shimming the MC away from the booster.