[krehmkej]

I am planning to change the power brakes on my Ranchero to a Hydroboost system. The Hydroboost unit I have is from a 1-ton diesel pickup, and has a 1-5/16" bore master cylinder. The ranchero's present M/C has a 1" bore. With all things being equal, I know that increasing bore size will increase pedal effort/lower pressure in the lines. Thhis leads to the question: Does the added boost of the hydro offset the bore size issue? An unknown is the pedal linkage ratio of the donor vehicle (86 K30). Options I have are to stay with the 1-5/16" cylinder or find a 1" one that will fit the HB.

Thoughts, anyone?

thanks,

[xntrik]

I had a new 77 Ford Country Squire 460 trailer package that had hydroboost on it. You might check that MC.

I also saw an 80 Mercury Monarch (Granada) with front discs only that had hydroboost. I have been kicking myself ever since for not getting the HB from it before it hit the crusher. It had an 8.7 rear that I put into a Versailles that I got the 9" disc rear out of. The front discs went onto a 65 Falcon.

[66GMC]

Originally Posted by krehmkej

I am planning to change the power brakes on my Ranchero to a Hydroboost system. The Hydroboost unit I have is from a 1-ton diesel pickup, and has a 1-5/16" bore master cylinder. The ranchero's present M/C has a 1" bore. With all things being equal, I know that increasing bore size will increase pedal effort/lower pressure in the lines. Thhis leads to the question: Does the added boost of the hydro offset the bore size issue? An unknown is the pedal linkage ratio of the donor vehicle (86 K30). Options I have are to stay with the 1-5/16" cylinder or find a 1" one that will fit the HB.

Thoughts, anyone?

thanks,

There's a good chance that I'm assuming wrong here, but I thought that almost all master cylinders mount up universally. (2-bolt mount)

The original single system MC on my 66 GMC was the same mounting as the split-sytem (dual) MC from the 79 GMC.

Have you tried bolting the Ranchero M/C up to the GM H/B?
Did the Ranchero have power (vacuum) brakes previously?

I guess what I'm getting at is that you may already have the correct master cylinder, and possibly the factory Ranchero brake pedal and rod may also work with the HB. Most of the brake parts are mfr'd by the same vendor (ie Bendix, Wagner)

As far as I know ... the method of providing pedal effort assistance (hydroboost or vacuum) is the only difference ... and you're just substituting one for the other.


73(?) Ranchero (You didn't say what year)


One of two (Stamped "1605") that fit an 86 K30


The other one (Stamped "1925")

The mounting on all 3 looks the same to me ...
What do the rest of you guys think ... am I nuts?

[krehmkej]

First thought was just mounting the Ranchero (78) MC to the Hydroboost. Discovered that the Chevy uses a 3.4" center to center measurement, whereas the Ford is 3.2" That would mean "hogging" out the mounting holes, or rotating the HB 90 degrees and making an adaptor AND a new pushrod. So, trying to keep it simple, just figured to get a smaller diameter Chevy MC if bore is truly an issue.

[66GMC]

Originally Posted by krehmkej

First thought was just mounting the Ranchero (78) MC to the Hydroboost. Discovered that the Chevy uses a 3.4" center to center measurement, whereas the Ford is 3.2" That would mean "hogging" out the mounting holes, or rotating the HB 90 degrees and making an adaptor AND a new pushrod. So, trying to keep it simple, just figured to get a smaller diameter Chevy MC if bore is truly an issue.

3.4" vs 3.2" ... bummer.

In addition to the bore sizes, you will also probably want to find an MC with the same sized fittings ON THE SAME SIDE, otherwise you are looking at adapter fittings and/or re-plumbing. <sheesh>


I would expect the GM hydrobosster to have Metric O-ring fittings on the hoses as well, whereas your Ranchero probably uses inverted flare fittings, right?

It mighty be easier to find or order a "Ford" hydrobooster or a custom-fit kit?

These guys make custom hydroboost kits. Be sure to check out the movies in the Multimedia section.

[Triaged]

Hydro-boost adds a lot of boost. What do you have to loose trying it? A few $5 adapters to hook it up to your brake lines? Hook it up and try it out. If there is too much pedal effort just buy a smaller GM master.

[37OldsCoupe]

Did you look to see if a master cylinder from a 5.7 diesel with hydroboost will work?

Rick

[krehmkej]

Good thought. Did not even know they had such a small diesel. 1/2 ton pickup? I was given the whole setup and would like to use as much as possible after a good cleaning.

[joe_padavano]

The 5.7 diesel is the ill-fated Oldsmobile diesel (die-sell). It was used in a wide variety of GM cars and trucks from the mid-1970s through at least 1982. All used a hydroboost brake booster.

Note that if you're mixing and matching master cylinders, you need to watch for the booster-to-MC pushrod length.

[krehmkej]

I hear you on the pushrod length issue. If the 1-ton MC doesn't work out I plan to just take it to NAPA and dig through their selection on Chevy ones.

[66GMC]

Originally Posted by krehmkej

I hear you on the pushrod length issue. If the 1-ton MC doesn't work out I plan to just take it to NAPA and dig through their selection on Chevy ones.

Just so you know ... that booster-to-m/cyl rod (and associated hardware) is NOT included with either the remanufactured NAPA booster or master cylinder.

All of the parts in this picture were "harvested" from an auto-wecker unit, and used with the reman NAPA components.

[krehmkej]

Interesting picture. Thanks. I had thought that the brake pedal to HB rod was "staked" in. Obviously not the case. This unit came from a running truck. I had not planned to open it up - my manual says it cannot be worked on, replace as a unit. Obviously these pieces came out without difficulty. If possible, I would like to remove the brake pedal rod to shorten it rather than doing that with it in place.

[powerrodsmike]

I would think that the 1 5/16 MC is way too big for your Ranchero calipers. Check the piston size difference of the truck calipers to your car calipers and I'll bet there is a difference.
The brakes will be so touchy it will be painful to drive.

I would look at a 1 1/8 or a 1" bore that will fit the HB unit.

Later, mikey

[66GMC]

Originally Posted by krehmkej

Interesting picture. Thanks. I had thought that the brake pedal to HB rod was "staked" in. Obviously not the case. This unit came from a running truck. I had not planned to open it up - my manual says it cannot be worked on, replace as a unit. Obviously these pieces came out without difficulty. If possible, I would like to remove the brake pedal rod to shorten it rather than doing that with it in place.

I think there was a locking clip that held the pushrod (Pedal to HB) that you can release by sliding a tubular object along the rod.

None of this stuff is internal to the HB unit ... they're right ... not user serviceable.

The star-shaped clip, spring, and intermediate rod are in between the HB and the MC.

The external snap-ring was behind the HB to firewall retaining nut, and is designed to make sure that the nut cannot possible vibrate loose and fall off.

The remaining items are a pre-bent return line, hose mounting bracket, and tube clip.

[joe_padavano]

Originally Posted by 66GMC

None of this stuff is internal to the HB unit ... they're right ... not user serviceable.

That's not true. My 86 Chevy truck service manual details how to rebuild a hydroboost. There are rebuild kits periodically offered on ebay for $40-50. A lot cheaper than the $250 for a rebuilt unit.

Note for the last 20 years or so, GM has broken its service manuals up and publishes a separate "Unit Repair Manual". That's where the info on rebuilding the brake boosters, steering boxes, transmissions, and axles is located.