71cutlass350

I've done some digging all over the but haven't found the info I'm looking for. I bought a low mile rebuilt 350 from my 71 project and the engine has a pretty radical cam, which equals no vacuum for my power disc/drums. Looking at doing a hydroboost setup rather than a vacuum pump and trying to figure out my options. I found a guy who has a 84 Hurst parts car that has the hydroboost and power-steering pump. I'm guessing the pump will swap over no problems and ill get custom hoses, I'm planning on reusing my MC and proportioning valve, just curious if the hydroboost will bolt up to my MC and if it will bolt to the firewall without new holes or a bracket.
I know the more common swap is using a hydroboost from a Astro van or a HD 80's-90's truck but i belove those take some extra fab work, and I'd prefer to keep this as simple as possible and this looks promising.

Lsx442

Do you know any details of the hydroboost system like the brand? I think a GM master should bolt up. Is he not selling the master with the setup?

71cutlass350

Its a factory GM unit, I know the diesels came with hydroboost, but I guess I'm not sure if the H/O came with vacuum or hydraulic boosters.

VC455

I understand that a hydro-boost will work with any source of hydraulic pressure. My friends didn't change their pumps when they added hydro-boost.

I went the vacuum pump route. I got a salvage pump from an 80s Cimarron. The only time it comes on is when starting, or if I have to use the brakes more than twice in a row with the engine at idle. It hides under the driver fender and the vacuum lines run over the wheel-well so you don't see much of anything different from the way the car was born.

oddball

I put hydroboost in my '72 and overall I'm very happy with it. It did take quite a bit of work though.

Pump: There's lots of gnashing of teeth about pumps out there. I'm firmly of the opinion, after waaaay too much money, that any health Saginaw pump with regular gear output (not the lowered mustang rack output) will work just fine.

Plumbing: Do you have power steering? The booster bypasses most of the pump's output, and that high pressure fluid has to go somewhere. Don't want that shooting straight into a reservoir. Making custom high pressure AN hose is the easiest, but most expensive, method. Folks have worked out various approaches with stock parts. That's tough because of the mix of fittings (all boosters are late metric fittings) and routing (stock parts tend to have elaborate bent hard line sections).

Booster: (Nearly?) All hydro boosters are identical. The mounting plate/bracket is held on by a very large (1.5"-ish??) unusually shaped nut at >150 ft/lbs. The plate/bracket is custom per application. Some are flat plates with the same pattern as the back of the vacuum booster, so you can put vacuum booster brackets on it and call it a day. Others sell custom brackets, like Tallon Hydraulics and "sterlingworth16" on ebay.

Master: The booster has the common GM master mount, so it will bolt up. BUT: there were many different piston lengths and many variations of masters. So you have to measure and/or experiment to make sure the piston sits just short (0.010"-ish) of the master. If the piston engages the master all the time then the brakes will not bleed or load properly.

Pedal: The mount may line up with the manual hole on the pedal or the power hole on the pedal. I'm using the 80's Dodge D150 master, and it works *much* better with the manual hole, but the bracket I have lines up with the power hole. Hence more work remains. Mis-alignment will make the pedal feel a little bound up and will eventually wear out the bore in the booster.

71cutlass350

Yes I do have power steering and I'm converting the box to the Jeep G/C box so the lines from the HB to box should be metric on both ends, and for the rest of the lines hoping to use factory lines from other cars and hopefully making that work rather than paying a lot for custom hoses.

I actually ended up finding a pretty good thread with lots of details on the swap so I'll post it here for other in the future.
http://transamcountry.com/community/...?topic=65835.0

And after looking at my options I think I'll try and find an astro HB unit for cheap from a junk yard and buy an adapter online. I think I'll also reuse my stock pump and either add another return bung or use a T fitting.

oddball

T fitting (just hook it up the right way - booster goes on the leg, gear and reservoir straight through) works fine or if you're feeling fancy, a fuel Y-block.

I pulled a couple of boosters from yards. Unfortunately they were trashed - exposed to the elements for too long. Rebuild kits are available (e.g. MBM Brakes), and they're fairly simple units, so just be sure to tear it down and inspect the internals.

oddball

Whoops, forgot about the brake pedal rod.

Most stock hydro applications used an eye bolt to connect to the brake pedal. We need a threaded rod holding a clevis. The pedal rod is staked into the hydro unit. You can find instructions for removing it (usually has to be removed in order to rebuild the unit) and folks like Talon sell replacement rods.

If you get a tailored unit then it'll have the correct rod and bracket.

csouth

As stated above the hydroboost units will be either long or short rods deoending on the vehicle. That will determine which master cylinder you can use. You also need the correct bore master. Mismatching the system can make the brakes very touchy from what some users have told me.

joe_padavano

Consider avoiding all this work and simply converting to manual brakes. My 70 W-30 4spd stops just fine with factory manual disc brakes. Pedal force is not excessive.

71cutlass350

I haven't ruled out manual brakes at this point just figured I'd see what it would all take to do hydroboost. The extra work doesn't bother me as much, it would be different and I don't mind a challenge. But just looking at options as of now. If I did consider manual disc brakes, would I be able to use the same MC and just ditch the proportioning valve and get some manual brake lines?

joe_padavano

Manual disc brakes use a 1" master cylinder. Power disc brakes use a 1.125" M/C. The difference in piston area is to make up for the lack of boost. You are trading increased pedal travel distance for lower pedal force to get the same line pressure.

You still need a prop valve - that has no relation to the manual vs. power.

cherokeepeople

hey where you at in iowa.we might have a diesel car or two around that could be parted out for the HB and p.s. pump.you need a HB p.s. pump as it has an extra return line off the HB.

joe_padavano

There are bolt-in kits available for installing a hydroboost in the A-body cars (look for Chevelle kits).

Hot Rod ran an article about adapting a junkyard hydroboost and M/C from an Astro van to a Chevelle.

71cutlass350

I'm from north of dubuque but go to school in ames so I make that drive quite often.

cherokeepeople

ok wrong side of state.