you have to make the rod it was posted earlier. there is about 3/4" difference between the too. take a few pics and post them when you do this if you can so everyone can see how it is supposed to be. doesn't sound too hard to do but it is hard for me to picture without the stuff in front of me.

 

Your talking about the rod that goes to the brake pedal, I mean the push rod that goes from the HB to the master.

 

oh I am pretty sure it is the same

 

ok unbolt your master from your factory brake booster and a pushrod about 2 inches long will come out. It has nothing to do with the rod that bolts to your brake pedal although that does need lengthened due to the shorter rod on the HB unit. Your getting them confused they are two differnet things.

 

no I know what you are saying. The rod for the hb to the master is the same but you need to machine the ID on the hb to fit the master or use a 4th gen master which is supposed to be a direct fit. the rod to the brake pedal needs modded to work.

 

I am getting ready to do this mod. I have:

- a hydraulic brake boost unit out of a 94 GMC Safari (equivalent to Astro)
- a new steering box (IROC quick ratio)
- 16mm and 18mm x 1.5 steel o-ring to -6AN adapter fittings from KRC Power Steering (for the steering gear box and the boost unit)
- 4th gen LS1 master cylinder
- sawn-off pedal rod from the original vacuum boost unit

A few weeks ago I put some paint on the steering gear box and the hydroboost and installed the -6AN adapter fittings. I just wanted to make sure that I have more/less everything necessary to install this. I was planning on welding in some 3/8" all-thread on the pedal side of the hydroboost, then threading the original pedal rod. A coupler could then be adjusted for the right amount of "jiggle" on the brake pedal. Are there any other tricks to this setup?

 

it sounds like you have everything. put up some pics of the whole process if you get time. It would be an easy sticky on here.

 

I can take some pictures of the parts, and as much of the process I go through right now. The engine compartment is completely stripped for fresh paint (no engine, tranny, etc). I won't be putting on the master cylinder or testing the brakes for quite some time. I'll try to get some photos of hooking up the pedal rod. It is a tough spot to take pictures, that's for sure.

 

What has to be modified on the 3rd gen master to make it work..?
Does the OD or the length of the master cyl. part that fits into the HB need to be reduced (by 0.050" per previous post).

I plan on doing a C4HD brake swap and wad told that I must run a disk/drum 3rd gen master.

 

Mine is complete and looks great. I will be bolting on my heads, intake and turbos next week and have a new steering box from red head on its way and should be able to drive it next week sometime.

I went with the 4th gen master because it cleans up the engine bay and I like the cap design it actualy seals shut. You can use the 3rd gen master you just need to shave off the material on the OD so it will slide into the HB. The lenghth of the 3rd gen master is fine.

This realy is an easy mod. The rod on the back of the HB is about an inch short. I just cut it of and put an adustable jam nut and welded the old pedal end on my HB.

 

I want to do this mod especially since my power steering fluid is leaking. but Im aprehensive about shortening the rod. I'm not good at welding.
I have V-belts if I use the astro pump is it possible to swap out the pully?

 

yeah but make sure you don't change the ratio on the pulley or it will affect the output of the pump. and you have to add to the rod not shorten it.

 

I don't have access to a third gen master cylinder, but my fourth gen unit has an OD of 1.469" or 1-15/32" for that bore in the back, if you're interested in modifying your existing third gen unit.

My fourth gen master cylinder box says:

AC Delco #18M971
GM #89056526

I believe I got it from Rock Auto.

 

I took some pictures of the parts I'm using for this mod:

- hydroboost unit, with a fresh coat of paint and the KRC adapter fittings
- brake pedal rod from third gen vacuum booster
- vacuum brake booster bracket

 

ok so no one has comfirmed the the 4th gen does bolt right up. superirocz, does it? so what you need to do once removing the old is...
1.bolt on the old vaccum booster bracket
2.bolt on the astro HB
3.bolt on a 4th gen master cyl
4.plumb it up
5.and shorten the pedal rod under the dash

thats all there is to it?

 

here is my pump and the rod looks like it could work without changing anything. I am going to try and get it mounted without messing with the rod. Looks like it may be done.

 

the 4th gen will bolt up but it must be a 98+/ls-1 4th gen. I got my car running but have not driven it down the road yet. In my driveway the HB seems to be working great.

 

was yours (hb pump) the same style rod as the one I have pictured above or different? Did you have to change it? I haven't even started on mine yet.

 

it looks just like mine was. You will need to shorten it about an inch but take measurements to be exact. What I did was cut most of the HB rod off and put a threaded lock nut/bolt so I have some adjustement with length and while your at it may as well weld your factory rod onto the threaded bolt so it will silde over the brade pedal. The HB rod end is much larger in diameter that the stock rod on your vacum setup.

 

Are 4th gen master cylinders required? I would rather use a 3rd gen one since they are $30 for a remanufactured one vs over $100. Just in case I want I ever need to replace them or decide to go with new parts.

 

you would have to get the hydroboost pump machined to use our master cylinders but look on ebay and a couple sponser sites and you can find a ls1 master cylinder for about $30 also.

 

Old thread!

Guys using the van unit. I bought a new one, so i gotta find a spring, retainer, and pushrod for the MC side.

The spring keeps the cylinder in I take it? I noticed that it wants to spring forward towards the master, which is making it difficult for me so I know what size to make my rod on the rear side for the pedal.

Anyone know off hand if I can get the spring kit separate? I bought a new unit so I wouldn't have to rob a van in the middle of the winter

-- Joe

 

I still have not done this on any of my f-body cars yet, but it will happen.

As for the springs, I'm not sure what spring you mean. You should have one pushrod coming out the front to push the master cylinder and one going in through the back to hook to the brake pedal. On the cars and pickups that I have converted, I have used the master cylinder that matched the hydroboost unit. I don't remember a spring being inside there.

My plan is to take my car's master cylinder and to have the housing machined down to properly fit into the donor vehicle's hydroboost unit. If you are using an Astro van hydroboost, then use an Astro van master cylinder as the guide. Take both housings to the machine shop and tell them to make the f car unit flange match the astro flange.

The pushrod on the backside that goes to the pedal, well, I usually cut that one down until the rod fits the pedal just like the old one did. I usually do have to use a die grinder or reamer drill bit to enlarge the pedal hole because every hydroboost unit that I have had used a larger pin than the vacuum style.

Hope this helps and please take lots of pictures to help the rest of us who are still war-gaming this operation.

--KrisW

 

I'm using an LS1 master which fits fine. On the hydro boost unit, on the MC side, you have a pushrod, a spring, and a spring retainer. The new unit says to use these items from the old unit. I don't have an old unit so I will have to hit the junk yard tomorrow.

The spring I'm guessing keeps the hydro cylinder preloaded.

In this picture:



You see the pushrod, and the retainer which is locked into the channel. The spring is behind it.

See:




-- Joe

 

Thanks for the pics.

I guess the reason I never saw the spring is that it was always in the old unit. I only ever used old units hahahha.

 

Also, forgot to add, when you are working out the return from the hydroboost to the reservoir, do mod your reservoir to accept a second return line up high. The return that tees into the one line didn't work so well for GM on the pickups, and they got converted over to two return lines in the mid 80's.

 

There are TWO different length rods from the factory. one is from what I remeber about 1/4" shorter than the other. Both use the same retainer star washer and the same spring to just hold the rod in place for the pedal travel. If you put in in and the pedal is too much play prior to engagement, you will need the longer of the two rods. No one sells them new from what I was able to find- I found a used one from the guys at ABS in Orange Calif for $5.

The original shorter one I had was from out of an astro van. I do not know what vehicle has the OEM longer one

 

Yeah I have not decided how I'm doing that yet. I'm tempted to just tap a 3/8" NPT on teh top of the pump for the second return, but I don't know if that will create foam.

I'd swap pumps and go with a remove res, but removing the pump is a project on my car because the supercharger bracket is in the way.

I wonder if I could replace the pump tank with a canister style (for remote res) with the pump in place. I bet it won't slide far enough of the back before crashing into the block.

-- Joe

 

That should be easy to figure out. The spring and retainer is the most important part, the rod can be fabricated. I'd just measure the dept of the cylinder once the retainer is holding it back, measure how far into the cavity the master goes and you've got your target distance.

Is the rod that came out of the vac booster longer/shorter ? I don't know where mine went, when I took it out it must have rolled away haha.

-- Joe

 

I don't know if you guys measured or not but this is what I came up with.

The pushrod between the pedal and the back of the hydro is 7 1/4". I made mine adjustable between 6 3/4 - 7 3/4.

I picked up a retainer, pushrod, and spring for the master cylinder side out of a van in the junk yard. The rod was way long. After some trial and error, I found that with the hydro ALL THE WAY IN, I needed the pushrod to be 2 inches (like 2.100") with the LS1 master. Any longer and it would hang the master open a hair.

I gotta pick up some 10MM nuts for the 4 studs. For hoses, I'm using autozone # 91651. They are only $14 each and they are the right length. each hose has an 18MM and a 16MM end. One obviously from the pump (16MM) to the 18MM on the hydro. Then the 16MM on the hydro to the 18MM on the steering box.

The rubber gromet that goes to the firewall and shrouds the pushrod needs to be shortened by 1/2" or it will bind on the pushrod.

I used my 240volt mig when I re-welded the rod for the pedal. This needs some serious consideration because if the weld fails you die. I had the wire speed set to about 2, and the head quite high (about 120amps).

-- Joe

 

A truck power steering pump won't fit the stock serpentine brackets because the top of the pump is too wide.

Is anyone aware of a pump that has a skinny neck/tank but two returns?

I'm worried about a pump with a remote tank as my blower takes up a lot of room on that side of the engine bay.

-- Joe

 

On my Jeep truck that I converted, I drilled a hole in the back of the neck on the top of the reservoir, threaded a cut off piece of brake line through the hole, and J-B welded it for a seal. It never leaked. If you're handy with a mig welder you can make it nice by just welding it in.

With the cap off and engine running I could see the return oil flowing back into the reservoir, and no foaming to speak off.

I did the same thing with my second diesel fuel return line that I plumbed into the fuel filler neck. Its what I plan to do to mine too.

 

For OEM pump housings, try the G body cars that came diesel equipped with the Olds 350 diesel. I seem to remember them having two returns down low on the housing on the 83/84/85-ish model years.

Vin code N

 

They use a #6037 pump, which is wide like the truck pump.

Even the Fbody pump is like literally against the aluminum bracket, so their is no chance of a wide body tank fitting.

Did some reading and the valving on the hydro pumps is different than the non hydro pumps, so if I could get my hands on a hydro pump that fits it would be ideal.

-- Joe

 

I'm not sure what that difference might be, but my Jeep ran a non hydro Saginaw steering pump and I had no adverse affects after hooking it up.

 

Not a 3rd gen- I have it on Vetruck- but it may help you with ideas.

 

I decided to go with an Astro PS pump as well, autozone # 7079, and an external reservoir. Hopefully have some pictures over the weekend of the completed unit.

The routing is as follows:

Pump high side (16MM) into hydroboost (18MM port)
Hydroboost high out (16MM) into steering box (18MM port)
Return from power steering box direct to pump return.
Return from hydroboost to astrovan reservoir.

-- Joe

 

Sorry to be THAT guy that drags up an old thread, but, did anyone ever find a source for the Master Cylinder pushrod, spring, and retainer clip when using the 2000 G2500 booster? I just ran into that problem because I ordered before I read the entire thread and now I am searching for the solution for this. If a person was able to make a rod, is the spring required for pre-loading the hydroboost unit?

 

I grabbed 'em out of a junkyard.

-- Joe

 

For anybody that ever finds this and needs to know, the guys at Tallon Hydraulics (who I am not affiliated with in any way at all) knew exactly the spring, retainer, and master cylinder pushrod I needed as soon as I said what I had. Give them a call if you end up buying remanned and cannot find one of these in a Junkyard like I couldn't locally. http://www.tallonhydraulics.com/ I should get them next week and I'll let you all know if they work like they should.