Most Annoying Search...Hydrobooster

[C10forDad]

I am about to go to manual brakes because I can't find a clear answer to this question...

What hydraulic booster pairs up exactly with a master cylinder with a 1.125 " bore?

Currently there isn't a parts store around me where I can walk in with my Wilwood master cylinder (PN 261-13270-BK) for a test fit. I also cannot fathom paying $600 for Hydrastop.

Things that I do know...

81 and newer have metric lines and before that was standard
These boosters were in everything from 3/4 ton pickups, vans, and more
They were installed in both gas and diesel vehicles
There are a dizzying varieties of mounting plates -> equal number of part numbers

There are too many posts that say grabbed one out of or for an Astro, old square body diesel, or something else without mentioning a part number

There has to be someone on here that has a part number.

[C10forDad]

Here's that nice firewall and some countersunk washers and screws that playing around with

[Rust_never_sleeps]

You might call Summit and ask about their reman Cardone units. Spec doesn't indicate MC size on this one, but there are numerous options:
https://www.summitracing.com/parts/aaz-52-7409#overview

[Joyridin]

It is going to be a bit hard as the print for your master cylinder does not have the pilot dimension. It looks like the holes are slotted, but not sure how much. My hydroboost bolt pattern is 3.34" roughly from center to center of master cylinder mounting holes.

This is what I used.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Here is the master I used. You can look up the dimensions on the Cardone site.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Keith Seymore]

Random brake chart, since I had it scanned and it is a clear copy:

[Keith Seymore]

It looks like "none", at least originally.

These are all paired with 30mm or 31.8mm bores.

My guess would be the 1.125 (28.6mm) master cylinder is the same on the outside as the other masters.

K

[Jason Banks]

I have a hydroboost setup from a 2002 silverado 2500 and the exact same Wilwood master cylinder you mention sitting on the shelf(because I swapped it for smaller bore). When I get to the shop, I'll see if I can dig out the hydroboost and see if they will work together. I am 99% sure they will, because I'm pretty sure the mating surface on the master cylinder's are the same regardless of bore.

edit: looks like the Hydroboost joyridin links above is the same as the one I have.

[Jason Banks]

Pic 1

[Jason Banks]

Pic 2

[Jason Banks]

Pic 3 4 5

[Jason Banks]

The Wilwood bolts up to the hydroboost just fine. I didn't put the additional pushrod plunger in the back of the Wilwood, and I didn't get my pushrod measuring tool out, but it appears that would not be an issue either.

You can see in the pictures the diameter of the protrusion on the mounting surface of the Wilwood is about 3/8 smaller diameter than the master cylinder that came on the 2002 Silverado 2500.

[Dashman]

I used a GM 15854059 for a 2005 Silverado 2500, and a JB7 master cylinder with 1-1/4 bore. You may find a hydroboost that was specifically for a 1-1/8" bore master cylinder. Sorry, I don't know of one.

I called Bosch Automotive: https://www.boschautoparts.com/contact-us.
They seemed especially helpful even though I had a GM hydroboost.

I also used:

...a custom bracket from this guy: https://customfab-cda.com/.

...a clevis type brake pedal rod, and a sleeve welded to the uncut end of the GM brake pedal rod so I wouldn't have to pull it out from its stake.

...metric to JIC fitting adapters typically found on Summit, Jegs, or Amazon.

...Gates Gates 6G-7MIX90 - G25504-0607, and it's 5/8" counterpart 6G-7MIX90 - G25504-0606. They are short leg 90 degree fittings that fitting under the inner fender/wheel well.

...custom hoses from a hydraulic shop.

I had to fabricate my own custom socket to remove the hydroboost from the original bracket. I ended up having to re-clearance my hydroboost rod, so it had the recommended 0.020" gap. The original brake pedal hole was too deep into the brake pedal lever that I opted to drill my own hole that centered the rod. In doing so, I reduce my brake pedal ratio. Whatever bracket you get, I would recommend that you place the hydroboost as high in the firewall hole as you can to use a hole that is the same distance down from the pivot or shorter.

[57taskforce]

My 72 K20 has an 09 silverado 3500 hydraboost with I believe a 1 1/8 bore master originally for the K20 and I had no issues. I’m not sure how different the hydroboost units are from application to application. I’ve got some industrial cores from some airport equipment that externally are the exact same as the unit in my truck. I do know that the accumulators are different based on application, which can be seen by the different colored cans on the outside of the booster assembly.

[C10forDad]

Thanks everyone for your valuable suggestions. I ended up getting the one that Dashman used since it was the only one available in my area on short notice.

A good friend of mine fabricated this adapter plate so I can mount it straight to the firewall. I'll have to get it installed all the way but it looks like I'll need to use a different length rod