Weird hydroboost question

[BigSix]

So I got the astro van hydroboost on the firewall captain fab bracket. The pushrod that the hydroboost pushes against the master cylinder is not adjustable. I yanked it out and tried to install my adjustable one...no go it won't clip in. So I gently tapped the stock pushrod back in. So what are my options in terms of adjustable push rods AND/OR a different master (that is all metal not plastic)?

[Twisted78SS]

Curious as well
Just getting to mine in the next week
I did gather a bunch of info but can't access it until tomorrow. I'll post what I have then

[BigSix]

Thanks - would be good to have an option for drum/drum and disk/drum and disk/disk just so it can be pulled up for others in the future. Really hoping I don't have to run the factory 94 Astro van booster

[Ozzy2013]

I took the half from a stock MC vacuum booster it unscrews in the middle .You then thread the hydro boost one to match.I didn't have that luxury helper lost the stock one so i cut the hydro-boost one and another one i found that matched the pedal hole and welded them together the length i needed.Bevel the ends fill them with weld grind down if preferred and it will look stock!

[Captainfab]

So what master cylinder are you trying to bolt up to the hydroboost that isn't working correctly?

[BigSix]

Originally Posted by Ozzy2013

I took the half from a stock MC vacuum booster it unscrews in the middle .You then thread the hydro boost one to match.I didn't have that luxury helper lost the stock one so i cut the hydro-boost one and another one i found that matched the pedal hole and welded them together the length i needed.Bevel the ends fill them with weld grind down if preferred and it will look stock!

I believe you are talking about the pedal side and I need the MC side.

[BigSix]

Originally Posted by Captainfab

So what master cylinder are you trying to bolt up to the hydroboost that isn't working correctly?

Right now I am drum/drum and have a 69 master but I should be getting a disk front and so really any master that is disk/drum and not all plastic would be good. Any suggestions for drum/drum in case my front disk doesn't happen would be good too.

[Ozzy2013]

Im talking about the pedal and hydroboost side you take the two join them the length you need and weld them together.

[bs46488]

Big Six,

You can use any MC that fits inside the bore of the Astro hydroboost. I think I ended up with a MC from a 1993 C3500, but some people like the old corvette mc's.

I bought a couple of lengths of pushrod and had to cut/grind them to a custom length.

[Twisted78SS]

I found some of the info I mentioned, here are some links to various threads. This is not what I thought I had gathered, but its all I have at the moment.


http://coloradok5.com/forums/showthread.php?t=306221

http://67-72chevytrucks.com/vboard/s...ferrerid=28772

http://67-72chevytrucks.com/vboard/s...3&postcount=46

http://67-72chevytrucks.com/vboard/s...d.php?t=372984

[BigSix]

Originally Posted by bs46488

Big Six,

You can use any MC that fits inside the bore of the Astro hydroboost. I think I ended up with a MC from a 1993 C3500, but some people like the old corvette mc's.

I bought a couple of lengths of pushrod and had to cut/grind them to a custom length.

So you recommend lengthening the stock astro pushrod? It is machined in the seat where it clips into the hydroboost so I think its best I add rod to it and then run whatever master I want. Right now I think since I will be going disk front I should consider getting an 80's truck master and I guess making my own pushrod.

Pedal side I will just cut, weld to stocker, and lengthen like I did when I went to power brakes originally.

[Ozzy2013]

I used a 1987 c30 master cylinder because thats where the hydroboost unit came from .You can use one of these older style or the newer plastic ones doesnt matter personal preference .

[BR3W CITY]

I just cut the adjustable end off and welded it onto the correct shaft. It took all of 7 minutes.

[Captainfab]

A '67-'70 drum/drum master cylinder requires the 'long' intermediate pushrod. A '71 and up C10, 20 or 30 master cylinder should require a short intermediate pushrod. I do know that in '79 a C10 was available with a diesel and a hydroboost. That would be a cast iron master cylinder.

All C/K 30's will have hydroboost brakes, but the master cylinder will have a bit bigger bore than a C10 will. This may make your brakes too touchy.

Originally Posted by BigSix

Right now I am drum/drum and have a 69 master but I should be getting a disk front and so really any master that is disk/drum and not all plastic would be good. Any suggestions for drum/drum in case my front disk doesn't happen would be good too.

[BigSix]

Originally Posted by Captainfab

A '67-'70 drum/drum master cylinder requires the 'long' intermediate pushrod. A '71 and up C10, 20 or 30 master cylinder should require a short intermediate pushrod. I do know that in '79 a C10 was available with a diesel and a hydroboost. That would be a cast iron master cylinder.

All C/K 30's will have hydroboost brakes, but the master cylinder will have a bit bigger bore than a C10 will. This may make your brakes too touchy.

So if I got the 71 and up C10 master - the pedal push rod would be something I could buy to mate to the hydroboost unit? What is the length on the intermediate pushrod and any idea where I would get that? The hydroboost pushrod has a different end on it than the vacuum booster pushrod.

[LostMy65]

Some have made the intermediate pushrod out of a bolt shank.

[Captainfab]

For the pedal to hydroboost pushrod, I would just cut both the hydroboost pushrod and your original pushrod and either weld them together or join them by a mechanical means. Most hydroboost units have the pushrod crimped in place and are not easily removed. I have seen a pic of a threaded pushrod for the hydroboost, but have not been able to find a source for it.

Was the back of the piston of the hydroboost master basically just a dimple or was it deeper like the '69 master you have? Do you know what the application was for the hydroboost you have? Most C10, 20 and 30 hydroboost units will have the short intermediate pushrod. I do have some hydroboost units and master cylinders from motorhomes based on the heavier C40 chassis which have a larger bore master cylinder and the deep piston bore and corresponding long intermediate pushrod.

Originally Posted by BigSix

So if I got the 71 and up C10 master - the pedal push rod would be something I could buy to mate to the hydroboost unit? What is the length on the intermediate pushrod and any idea where I would get that? The hydroboost pushrod has a different end on it than the vacuum booster pushrod.

[BigSix]

Originally Posted by Captainfab

For the pedal to hydroboost pushrod, I would just cut both the hydroboost pushrod and your original pushrod and either weld them together or join them by a mechanical means. Most hydroboost units have the pushrod crimped in place and are not easily removed. I have seen a pic of a threaded pushrod for the hydroboost, but have not been able to find a source for it.

Was the back of the piston of the hydroboost master basically just a dimple or was it deeper like the '69 master you have? Do you know what the application was for the hydroboost you have? Most C10, 20 and 30 hydroboost units will have the short intermediate pushrod. I do have some hydroboost units and master cylinders from motorhomes based on the heavier C40 chassis which have a larger bore master cylinder and the deep piston bore and corresponding long intermediate pushrod.

My hydroboost was from a 1995 Astro van I believe. The end that fits into the hydroboost is not plain - it has a groove machined into the side and it sort of clicks into place. I think I pulled it out with pliers the first time? Does this ring a bell at all?

[Captainfab]

I have not pulled an intermediate pushrod from a hydroboost, but I do know that they are retained inside somehow. If I remember correctly, you should be able to bolt up most any truck based disc/drum master cylinder as the Astro master cylinder should have had just a dimple in the back of the piston. I see no need to change the intermediate pushrod.

If you need a drum/drum master cylinder with just a dimple in the back of the piston, get a '70 Buick Estate wagon master cylinder. It is A1 Cardone 10-1363

Originally Posted by BigSix

My hydroboost was from a 1995 Astro van I believe. The end that fits into the hydroboost is not plain - it has a groove machined into the side and it sort of clicks into place. I think I pulled it out with pliers the first time? Does this ring a bell at all?

[BigSix]

Thanks! Glad I can reuse that rod! I assume the 71 C10 2wd was disk/drum? I think I can get one of those easy locally and its all cast which is nice looking to boot.

[Captainfab]

Yes a '71 C10 will be a disc/drum master cylinder and should have just the dimple in the back of the piston.

[BigSix]

Just to be sure that the 71 C10 master will work with my hydroboost - does this picture look like my intermediate rod will reach the dimple on the 71 C10 master?

[BigSix]

Oh and I assume I want the master from a 71 C10 with power brakes and not bendix brakes? Any particular proportioning valve to use with this master?

[Captainfab]

Yes a '71 master cylinder should work with that hydroboost. Any disc/drum proportioning valve will work. Use the one for the '71 if you have it..

[BigSix]

Thanks Cap'n