Hey, Bullitt, keep asking questions! I'm taking notes!

One thing I am not clear on. I have a 76 w/vac assist, front discs, rear drums. Is my master cylinder what I need? I don't quite get the discussion about proportioning valves and discs in the rear.

My impression is that I am OK with my MC because I am keeping my drums.

Sorry if this is a redundant question.

 

i'm not sure on the prop vavle, and someone will correct me if i am wrong, but i dont think you need aa prop valve if you are running all discs, or all drums. i believe you only need a prop valve if you are running discs and drums.

 

You will be ok with your proportioning valve but you will need the 78 master cylinder as the bolt spacing on the 78 mc will bolt up perfect to your hydroboost the 76 will not it is 3/16'' too narrow when it comes to spacing.

 

thanks for clearing that up

 

every hydroboost has a large snap ring on the back side of it that keep the bolt from backing off. Once you flip the plate and put the large lock nut in place install the snap ring back in the groove it came from.




And yes my mistake I meant the post 2001 trucks have a metric spacing not the pre 2001 trucks.



Well you guys can get a reman hydroboost from RockAuto that is for a 1990 F-SuperDuty for 138.00 if you are having a hard time finding them where you live. But out here they are common and cheap!

 

Come on guys keep the input coming! This thread could be useful information later on!

 

I should be heading to the junkyards Monday, but I think I might be looking at more Chebby's than Superduty's. All in all, the boosters look (according to NAPA pictures) exactly the same regardless of the vehicle type. The "iffy" part would be mounting the booster to the firewall and hooking up the pressure lines. I assume it may be possible the Chevy lines use a different style than the Fords, i.e. JIC adapters versus Boss and etc.

Josh

 

Just make sure you are looking at "newer" chebby's.

From what I recall the diesel trucks and blazers had hydroboosts back to the early 80's. Youd want something in the mid to late 90's at the earliest.

 

The early chevy hydroboost units have the same thread sizes and stud spacing. But the mounting plate is different and the pushrod is way too short.All these units are made by Bendix and are allmost the same.

 

Hmmm - that just fired up the old noggin.

I think I might just fabricate a new mounting plate rather than making an adapter to go from the bolt pattern of my hydro to the bolt pattern on the firewall.

I'll have a look at this tomorrow hopefully.

 

I was thinking of shortening the studs on the original SD Plate...then make a plate that matches the firewall holes....use spacers or make a spacer block to adjust the length of the rod to the correct length...bolt the original plate studs to the adapter plate and the fabbed plate to the firewall.

 

So, if I am getting this right, (chances are I am not because I am a bit lost in this thread,) one could get an early chevy boost set up and modify it to fit our firewall, and then simply lengthen the pushrod to compensate for pedal height? Or is the pushrod you are referring to the pushrod between the master and the hydroboost?

 

That was in essence what I was looking at and how most people do it. My "spacer" was going to be a solid aluminum billet and I was looking at through bolting both (hydroboost and firewall). Based on bolt locations, etc that gets kinda tricky - so I will either re-drill the hydroboost mounting plate to the firewall pattern and then use a machined spacer and through bolt, or just make a new plate for the hydroboost and use a machined spacer and through bolt.

You got it right the 1st time - we are referring to the pushrod that connects the pedal to the hydroboost unit.

 

The post 2001 Superduty and Chevy units need the push-rod longer?

Wow, when I swapped in my manual brake 1985 Ranger m/c I had to shorten several inches off of the pushrod, just guessing but I would reckon the pushrod is about 6 inches long (ok no laughing).

I am also seeing two techniques for the swap. One is bolting the booster directly to the firewall and the other it reusing the vacuum booster bracket.

How much harm is there is just drilling new holes in the firewall for whatever pattern the booster studs happen to be instead of making adaptor plates and such.

I called my local junkyard and a used Chevy booster is $18, plus $5 for each pressure line.

Josh
Josh

 

2001 hydro needs a SHORTER rod - hence the spacer on the firewall. I'm not positive about chebby boosters - but it looks like they need longer.


You can very wll punch new holes in the firewall. I am running a spacer because I have a 2001+ hydro with the longer pushrod and I don't want to mess with shortening the rod or moving my pedal closer to the seat (just gets annoying haivng to lift your foot that much higher to hit the brake pedal).