converting to Hydroboost Brakes

by bitterfitter Mon Jan 16, 2017 3:23 pm

What can you guys tell me about converting over to the hydroboost brakes? It seems like a win, win project as it makes more room and gives you better braking and no need for vacuum.

From what I understand it is the units from the Chevy Astro vans that are being used. The plumbing sounds like just some -AN fittings and lines. Do these bolt up to our cars as is or is there some fabrication needed? Also I can weld up a conversion rod but does it come out at the correct angle?

by Joe73 Mon Jan 16, 2017 3:48 pm

Just curious, what do you need the room for ? Or are you looking for extra vacuum for your cam?

Every time I see a guy at a car show with a vacuum can for their "big" cam, I chuckle because I know the motor needs timing and carb adjustment.

I've installed 2 comp cams 305 duration cams in a small block with no need for a vacuum can. I'm putting a 292 duration in my small block and I'm not thinking twice about a vac can.

I like the hydroboost but I'm not a fan of the extra hoses running up to the master cylinder. My pickup is hydroboost since its a diesel so I'm familiar with it.

Just wondering.

by bitterfitter Mon Jan 16, 2017 6:03 pm

To tell you the truth Joe, I am interested in a little of both. I am always looking for a better way to improve the systems of the car. I am always reminded that the parts on our car, even in brand new condition, were designed for a stock car as it came from the factory. Once we start raising the performance, we need to consider the other parts as well. The hydroboost seemed like it fit the bill for the brakes.

I am in the process of replacing most of the braking system on my car as it is old and starting to fail. I noticed when testing the booster this weekend, it will not hold vacuum so I have to replace it. This is when I remembered the hydroboost setup and thought I would look into it before I purchased a new vacuum booster.

Not that my cam is over the top or I am stuffing a huge engine under the hood, just trying to think about what would work best before I just replace the factory stock parts on a not-so-factory stock car. GoFast

by 73ss Mon Jan 16, 2017 6:31 pm

2 things to check, The check valve & grommet, and the rubber cup gasket under the master. That could be why it's not holding vacuum. These parts could be found in the "help" section of most parts stores years ago.

FWIW My 73 originally had a smaller single diaphragm booster. The big block & wagon models (in 73) got the larger dual diaphragm booster. At some point 75? all A bodys got the larger booster regardless of engine size. I installed the larger dual diaphragm from a monte and also the larger 11 inch rear drums from a 77 Elky. I'm pleased with the brakes, stops as well as any modern car and is trouble free. My motor pulls 12 1/2 inches of vacuum. The booster also holds 2 pumps after the engine is off.

by bitterfitter Mon Jan 16, 2017 6:36 pm

I didn't have a lot of time this weekend as I am installing new floors in the house, but I did check the check valve and grommet. They were not leaking at all. I am not familiar with the rubber cup gasket under the master cylinder. Is this located between the master cylinder and the booster? I remember changing my master cylinder a while back but do not remember any type of gasket there??

by 73ss Mon Jan 16, 2017 6:43 pm

Yes, in between. It's not so much a gasket but a seal that fits in the booster opening. shaped like a cup. The push rod comes through it.

by bitterfitter Mon Jan 16, 2017 7:02 pm

I will try to get out there tonight and check it out. Thanks for the tip.

by 73ss Mon Jan 16, 2017 9:47 pm

https://www.summitracing.com/parts/aaz-54-81001/overview/year/1973/make/chevrolet/model/chevelle

Heres a pic. click on the last pic. the rubber piece in the middle. Sometimes that piece gets cruddy and won't seal. A light coating of clear grease can soften it back up. If the MC was leaking it might be done. Also, Not trying to say hydroboost is bad. Just seems like it's heavy and more hoses and parts under the hood, if you don't really need it.

by bitterfitter Tue Jan 17, 2017 2:41 pm

I did get a few minutes to pull the master cylinder away from the booster. I am not sure if that seal is leaking but I did find the area full of fluid. It looks like the master cylinder must have been leaking out the rear. Surprising because I had replaced this one no more than a couple years ago and never driven the car since.

So now I am looking to replace the master cylinder also. So you guys are really not into the hydroboost? Guess I'll stick with the stock mastercylinder/booster.

by thatfnthing Tue Jan 17, 2017 3:02 pm

bitterfitter wrote:So now I am looking to replace the master cylinder also. So you guys are really not into the hydroboost? Guess I'll stick with the stock mastercylinder/booster.

I say go for it! I would have tried it if I hadn't gone the direction I did. I always find it fun and challenging to do something no one else is doing, and if it makes the car better and gets more attention at the cruise, it's a win-win. Fortune favors the bold!

by bitterfitter Sun Feb 05, 2017 2:06 am

So I did decide to continue with the hydroboost conversion. All has gone well and the unit is installed. I am changing my steering box while I have the power steering system drained. The one in the car goes about 2 1/2 turns lock to lock. I am looking for the same thing but with the metric connections. Am I correct the one I want is from a 92 camaro without the soft ride option?

by bitterfitter Sun Feb 05, 2017 2:08 am

Reason I'm changing box is that it is leaking everywhere. Not because of the connection threads. The one I'm talking about is part# 27-6550.

by crice63 Sun Apr 16, 2017 3:07 pm

bitterfitter wrote:So I did decide to continue with the hydroboost conversion. All has gone well and the unit is installed. I am changing my steering box while I have the power steering system drained. The one in the car goes about 2 1/2 turns lock to lock. I am looking for the same thing but with the metric connections. Am I correct the one I want is from a 92 camaro without the soft ride option?

Any more details on this? Pics? Did you get the part off a JY Astro, or order it new or reman? I guess your steering box was already metric connections, what about your pump?

by pila Sun Apr 16, 2017 4:02 pm

I had thought about a hydro boost brake in my '75 Elco. I thought the Caddy engine in it didn't have enough vacuum because of the cam. Turned out that the vacuum was enough, but the booster was from my '77 Elco that I bought new, and was OLD ! Replaced the booster, and now the brakes are great !! Simple things can ambush us sometimes... Surprised

by bitterfitter Sun Apr 16, 2017 5:56 pm

I can get some pics another day but here is what I ended up doing. I changed out my leaky gearbox with one from a 1992 Camaro WITHOUT soft ride suspension. I bought a hydroboost unit from an Astro van in a junk yard. The unit worked and could have been cleaned up but I decided to get a new one to make sure it looked and worked like new. NOTE!! When buying a new unit make sure it comes with the internal pushrod, spring and retainer. Mine did not and I had to harvest these from the used unit. They do not sell these parts separately!!
I used a brand new master cylinder which I already had. For the pump I just changed the threaded fitting in the rear. This can be bought new or harvested from the scrap yard. So at this point I had all metric fittings. For hoses I used a set from a 1985 Delta 88 with hydroboost. The diesels had hydroboost. I used a 3/8" brass Y to connect the returns to the pump.
One last note. You will have to modify the hydroboost brake pedal rod as they are short. I cut the rod off the back of my vacuum booster and threaded it. Then I also cut the end of the hydroboost rod and threaded it. Then used a threaded coupling to connect them and allow adjustments in length.

Sounds hard but pretty easy conversation. Brakes are rock solid every time I touch them. Steering is awesome also!! I love it.

by crice63 Mon Apr 17, 2017 10:52 am

So the Astro unit worked with our stock MC. Did you have to do anything with the firewall? Covering holes or making new ones?

by bitterfitter Mon Apr 17, 2017 11:05 am

Everything worked great. Just grind the rivets of the bracket that is attached to the back of the old vacuum booster and bolt it between the firewall and the hydroboost unit. I will post pics soon

by bitterfitter Mon Apr 17, 2017 11:18 am

Don't mind the wiring mess in the background. Also the middle and last picture show the hydroboost unit before I flipped it 180 degrees. The accumulator ends up towards the valve cover not towards the fender as in these 2 pics. Top picture shows how both the factory hoses from the Delta 88 worked out. Very pleased and it looks factory as I used all GM parts.

converting to Hydroboost Brakes Img_8110

converting to Hydroboost Brakes Img_8110

converting to Hydroboost Brakes Img_7911

converting to Hydroboost Brakes Img_7910

by bitterfitter Mon Apr 17, 2017 11:22 am

Here is that internal pushrod, spring and retainer that is needed and not usually supplied with a new unit. I bought a junkyard unit to strip these from.

converting to Hydroboost Brakes Img_8010

converting to Hydroboost Brakes Img_8010

by thatfnthing Mon Apr 17, 2017 2:23 pm

Now THAT is some fine car crafting, sir! cheers

by bitterfitter Mon Apr 17, 2017 2:27 pm

Thanks a lot! I finally snuck it out for a short street test on Saturday. The new fuel injection needs to be driven to self learn a little more.

I can tell you this much; the posi works great!! GoFast

by crice63 Mon Apr 17, 2017 5:39 pm

Interesting and very helpful pics and information. Did you order the delta 88 hoses new or find them at the JY? Also, why did you flip the unit--I thought on the Astros the hoses face down but just now I'm not certain.

Impressive work and great documentation.

by bitterfitter Mon Apr 17, 2017 7:23 pm

I bought the hoses new from the local auto parts store. They were like $12- $15 bucks each. As far as the rotation of the hydroboost unit; I installed it with the accumulator towards the valve cover because the hoses worked out good this way. I wanted to try and install it the other way but the hoses would not have worked. I think the way I installed it is the way it was originally.

by bigredlaguna Mon Apr 17, 2017 10:27 pm

Nice conversion! On a side note, I've never seen a master cylinder with the bleeder valves like that.

by bitterfitter Mon Apr 17, 2017 10:28 pm

I had a choice when buying it and figured this would help bench bleed the master.

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