Behold, Frankenbooster!

We4ever

Member
The back half is from a 79 cutlass diesel reman from auto zone.
The front half and piston is from a 1995 Chevy 3500 dually found in junk yard full of water.

The benefits of this rig: It fits gn firewall, It fits the stock pedal, and 84 regal power steering hoses fit.

Larger truck piston for SUPER brakes.

waiting on master cylinder to test.
 

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We4ever

Member
I've got a parallel thread on a gm truck forum. Trying to determine if I can fit a weaker master cylinder on this booster. Im worried the Jb8 will be a lockup monster or blow up my wheel cylinders. Also the truck I got the booster from had a proportioning valve that I didn't grab. Think I need one?
 
I'm using a hydroboost from a 1998 Astro van witch I'm pretty sure has the same bigger piston as your truck unit, a master cylinder from the same 98 Astro van but with a fluid reservoir off of a 95 Saturn SL (if I remember correctly), S-10 Blazer dual piston front brakes and a stock proportioning valve for the Buick and it all works together awesome! Wheel cylinders won't blow out simply from swapping to hydroboost unless you have a pre existing problem before the swap. Not sure if I'm understanding you correctly but there is really no such thing as a "weaker" master cylinder just different bore sizes that will affect the amount of pedal effort needed to get the same affect at the wheels.
 

We4ever

Member
Wheel cylinders won't blow out simply from swapping to hydroboost unless you have a pre existing problem before the swap. Not sure if I'm understanding you correctly but there is really no such thing as a "weaker" master cylinder just different bore sizes that will affect the amount of pedal effort needed to get the same affect at the wheels.
Thats why I asked. I used the word weaker because I figured the master from a 1 ton truck would generate more pressure in the line. I assumed a brake system designed to stop a huge truck and trailer would cause near instant lockup on a light car. Am I wrong? Im more than happy to be educated on this topic.

Im not sure about what master cylinders fit what boosters, i'm trying the 3500 at first just to guarantee proper fit (and its cheaper). I'll be happy to switch to something else after testing.
 

Chuck Leeper

Toxic old bastard
Staff member
I've used the smaller version of the HB on a few cars. The last being a 55 Chevy, with the Metric discs on the ft, Ford drums rear.
This was done as the 8" dual vac system would not stop the car.
I invested in a brake press gauge and found out why.
Less than 900 psi at the ft wheels.
The HB was installed, same mc, Wilwood adj prop, 2 psi residual check in rear.
The brake psi was then over 2000 psi Certainly didn't require much pedal pressure.
The aftermkt guys say there should be 1200psi, to work....NP here.

FWIW, the bucket list project 55:
13" Vette brakes in ft, 11.25" Ford discs rear, 15/16" mc, Wilwood adj prop, no booster.;)
 

We4ever

Member
Got it all bolted in yesterday and no surprise the piston seal on the junkyard half was weeping. Got a seal kit from pirate jack on the way, should be able to do a road test by Tuesday.

I think this might actually work!
 

TexasT

Texas, Where are you from
Can you post some pix of this and how you did the swap to the different front to rear when you do the pirate kit?
Thanx
 

We4ever

Member
When I first tried this job I was not sure if it was gonna work at all so, sadly, i did not document the construction. Despite this I believe I can demonstrate the procedure with the leftover parts.

The only significant internal difference between the 79 cutlass and 95 3500 boosters is the diameter of the main piston. Since we will be using the truck half to connect to the MC we need to swap the truck piston over to the cutlass shaft. This is technically a non-serviceable part, the piston is held to the shaft with a rivet. Drill out the rivet to free the piston and toggle thing that opens the spool valve. Take note of the orientation of the toggle before removal lol. Replace the rivet with another rivet or some kind of captive pin. Personally I used a teeny tiny nut and bolt that was left over from some gun or computer I built previously. Be sure to use threadlocker if you use a bolt.

At this point id recomend getting a rebuild kit and replace all the seals on the junkyard sourced half. Then re-assemble using the rear half from the cutlass and the front half from the truck, paint her up and shes ready to slap into the car.

I'm happy to report that this does indeed work and is currently the booster in my We-4. All told i'm in it about 250$. If you are of lower moral character than myself you could assemble the leftovers, paint and "return" to autozone. Likely the guy behind the counter wont notice the external differences and nobody will be the wiser until your garbage reaches the rebuild facility.
 

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We4ever

Member

This video shows how to change out the main piston seal. Be sure to put the new one in facing the same direction. Coating the new seal in grease makes the install much easier.
 

TexasT

Texas, Where are you from
Solid tech. I have a pirate rebuild kit. I think I have another 84 hydroboost unit I bought around somewhere. I will look for a truck unit next trip to the wrecking yard and am going to try this. I've been real happy with the 84 unit I swapped on yrs ago but they all seem to think without the accumulator I'm doomed. So I'll have this to try and use. Thanks for posting.
 

We4ever

Member
As far as I'm aware the only function of the accumulator is to provide you with enough reserve pressure to get you a few extra stops soyld you suffer engine or power steering failure. If you got strong legs it shouldn't be a problem.
 

TexasT

Texas, Where are you from
I have this hydroboost on our suburban and k2500 pickup. I've had the tensioner fail on the suburban and it is only good for another application or two of power brakes. It isn't like you don't have brakes. You just don't have power brakes. You don't have power steering either so there is that, too.
I have never had a problem with the Buick. But I guess if the tensioner or belt failed it could be a prob.
Either way, I love the idea and your execution. Great stuff!
 
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