Hydroboost
 

I'm planning on installing the Wildwood 4 wheel disk brakes system on my 70 GTO. It presently has power disk front, rear drums. And I presently use a small vacuum pump to get enough vacuum for the brakes. My engine only produce 8-10 mmhg. The Wildwood require 18+. I'm looking to get rid of the vacuum pump and go to a hydroboost system. What hydrboost system do you recommend for power 4 wheel disk brakes?

Honestly I would recommend going MANUAL brakes with a Wilwood set up. Easier, simpler, cleaner. AND WORKS! Need more bite? Then change pads. You'd be surprised how good a properly manual setup is.

Having just done a wilwood swap from an underperforming power booster setup myself, I recommend manual brakes.

Here's the problem with hydroboost in my opinion. The systems are largely a copy of what can be found on late 80's through earl 90's GM vans and some ford stuff like the mustangs of the late 90's and early 2000's. Those cars were designed with hydroboost in mind. In general they had power steering systems that were designed with the capacity to meet the flow and pressure demands of the hydroboost and calipers sized to counteract the incredible pressure the hydroboost sends to them.

In practice with these muscle cars, they tend to get put in front of a power steering pump that can't handle the brakes and the steering at the same time. They are also typically used in front of calipers that have very large pistons. This is why in a typical power boost setup on a GM muscle car, you see the use of the 1 1/8th" bore master cylinder, or even larger if available. You're trying to kill as much input pressure as possible in order to reduce the output pressure to the calipers. The problem with that approach is the fact that the larger bore master pushes a lot more fluid volume and the hydroboost is still creating a lot of line pressure. You end up with a very immediate "On/Off" brake pedal. There is typically very little feel in the brake pedal and because of the on/off nature of the brakes, there's very little in the way of modulation.

It makes performance driving terrible, if not almost impossible. Heck, it can make stop and go traffic terrible.

Going to a properly sized manual brake setup solves those issues, at the expense of a harder pedal. Not hard in a bad way however. It's not like the pedal you get when the brake booster isn't working. Needlessly hard without any stopping. It's a harder pedal that continues to travel, is actively stopping the car and is providing feedback to your foot on what the tires are doing.

If you're dedicated to doing the hydroboost, I would source your parts independently instead of buying a kit.

The Astro van's hydroboost I believe retains the bendix bolt pattern and should bolt right up to your 70GTO firewall. Take some length of hose and take measurements for your pressure and return lines and have them made by a local tractor company that does hydraulic lines. Or you can buy line kits too if that's more your speed.

You should address your pump at the same time. The original P Series saginaw pump is hard pressed to cut the muster for flow. It can't really run both the brakes and the steering at the same time. You'll want to go to somebody like Lee Power Steering that can build you a pump to handle the extra load on the system. Because you now have extra work the fluid has to do, you should also consider a power steering cooler while you're plumbing your lines. If you aerate your power steering fluid due to heat, you lose your brakes.

To retain a decent pedal, when purchasing your Wilwood kit, you may want to look at the calipers that have the smaller pistons in them. This may mean ordering direct from Wilwood. Their caliper offerings in kit form from places like Summit and Jegs usually err on the side of being the large piston versions that conform more naturally to the factory manual or brake booster setups in these cars.

I used Hydratech booster for mine. Great to deal with. Yes pedal is touchy, but you get used to it. Mine is on a 64 Lemans front disc rear drum system.
If your just streeting the car these will be fine. Is comes in different finish, I got the show finish one but was not as nice as I thought it should be.
These are brand new, not rebuilt units.
https://www.hydratechbraking.com/GM_A_Body.html

Thanks guys for the information. But I agree, with the Willwood 4 wheel disk system my best bet would be going to manual brakes. I'm thinking the bore on the power brake Mc is like 1-1/8, and probably won't work with manual brakes.
Anyone know the part # of the Willwood manual brakes MC?

Depending on which calipers you are going with on your wilwood setup will determine which size master you may need. I have the forged narrow superlight's on the front with a bit over 4" of piston area and the forged dynalights on the rear with about 3.5" of piston area. For this setup Wilwood recommended their 15/16" master. That recommendation has been working well for me.

If the calipers you are going with have smaller piston areas, you may want a 7/8" master.

7/8" Black E-Coat - 260-9439-BK
15/16" Black E-Coat - 260-13375-BK

There is also a polished and bare aluminum option. The polished is the same price as the black and the bare finish is about $50 buck less.

These come with the pushrod already installed. You may be able to re-use the clevis on your current power brake pushrod. I would also source an adjustable proportioning valve to plumb into the system. I'm using the Summit Racing adjustable block. It fits the factory line sizes correctly and makes installation a bit easier.

I have hydroboost on my car for the last five years and do not regret it one bit. It works flawlessly. I'm using the Astrovan unit on mine and using the original 1971 power steering pump. I'm not into braided line so I use hoses from a Cadillac Seville diesel. If your box is 1978 and older use hoses from 1978 Seville diesel, if your box is 1979 and newer use hoses from a 1979 and newer Seville. All of them are a direct bolt on. I use the aluminum master cylinder with plastic reservoir and proportioning valve from a 1981 Trans Am with 4 wheel disc. Of course, there are many choices out there. This car in particular has Wilwood calipers front and rear with 12" inch rotors. My braking is perfect but I will say I have an additional adjustable proportioning valve above my diff in addition to the regular one under the master to dial in perfect balance based on tire size(s) and caliper piston count/rotor size. My brakes do not do anything weird whatsoever. No noises, no leaks, no pulsation and maintains perfect pedal! I can't stress enough how well this set up works. In the eighties I hated hydroboost on anything and resisted this swap(They always leaked and had a weird pedal feel). I fought hard pedal since the early eighties due to large duration cams. BTW I was able to assemble all my parts for under $200.00 including the rebuild kit for the unit.

I run hydraboost system on both our cars. One of the best upgrades I've done. There's a reason the manufactures are using hydraboost units in new vehicles these days. I have friends running manual brakes in their muscle cars, and they also love it.

I've had hydroboost for almost 10 years now, and I'm very happy with it. The Le Mans stops like a modern car! (I also have 4 wheel disks)

GM has been using the hydro boost system in their light duty trucks, especially the diesel powered ones starting in 1988, I own 3 of these trucks with hydro boost on them. Two with disc/drum (K3500), and one with 4 wheel disc brakes (3500HD). other than a leaking boost unit (O ring seal), they have worked flawlessly, and all the trucks have over 250,000 miles on them. I don't have the on/off feel whatsoever, even in snow........:noidea:

I've also driven an Astro van with the hydro boost on snow, no hint of brake lockup, and if you're going to have modulation problems it will show up on ice/snow surfaces quickly.

My next street project will have hydro boost likely pirated from a GM light duty truck on it. Probably from a 3500HD with 4 wheel disc brakes.

BTW, all of my trucks do have a fluid cooler on them from GM, so likely it is needed in the system to operate properly.

Reduce weight, cost, clutter and complexity and go manual brakes.

As a bonus you no longer need that vacuum pump, less weight and clutter again. :)

In the end hydro boost is more trouble than it is worth.

From proper power steering pump, to reservoir or cooler mount height in engine bay, to hydraulic hoses etc

Simpler, easier, cleaner, better to just run a properly set up manual brake system. Plus less chance of failure.

Unless you have a physical problem that requires power brakes just go with manual brakes for the simplicity and ease of packaging. Besides it is way cheaper.

I put a Wilwwod 1" master and proportioning valve on my brother's 1970 LeMans with GM front disc/ rear drum and it works great and doesn't pollute the engine bay. I called Willwood to get their recommendation for the master cylinder bore size with the D52 calipers and they said use the 1" bore because of the large fluid input to the D52 calipers. I was thinking about using the 15/16" bore before I called them but the 1" works great.

Just to add, you should be able to increase your vacuum signal at idle with more timing advance. If you go to full manifold vacuum and limit it, it will help a lot.

If that doesn't give you what you want, you can upgrade to a dual diaphragm 9' booster, if you don't mind it not looking OE.

Manual is a very good option if the above all doesn't give you what you want.

My personal opinion, hydroboost has its place, but not on a muscle car. The driver experience kills it for me. Not to mention added complexity, troubleshooting, weight, and appearance.

The order of above suggestions creeps up on the 'problem' resolution and makes sense to approach it in that order. To me, anyway.

I have and do run some pretty 'radical' cams on the street compared to most, have about 11-13", and a dual diaphragm booster works for me.



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While I respect your opinion, Have you ever had or drove a muscle car with a Hydroboost brake system? and second, what about new vehicles that come from the factory with a hydroboost brake system.? Just curious.

Yes, I have driven both. But a newer car isn't a good example.

I sold my hydratech setup to someone on the boards, forget when that was. But the system was top notch. I test mounted it, hardware, everything was pretty spot-on as I recall. I may even have pics of it.

I bought it after driving a 70 Z28 with one, I was doing a blower build on my T/A and later bailed on the blower.

I think with a type II pump it probably would have been a better experience.

Again, my personal opinion/experience. Some are fine with them.

Here's the pic of when I sold it. The pic of it installed is hard to see, but the mount plate is kind of visible.


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Modern cars that utilize hydroboost have the entire brake and hydraulic system designed around it.

Generally they utilize a type II steering pump which typically has higher flow at lower pressures than the typical P-Series saginaw pumps found in most muscle cars. Additionally, the caliper sizes are designed along side the hydroboost to counter-act some of the pressure's it builds and helps to create a better pedal feel while adding modulation.

If you're re-engineering the entire brakes system (The OP might be), you can build it just like a newer factory car and probably get very similar results.

Retrofitting it directly into something that's already there usually creates a pedal that is very on or off. Some people do like that, I will concede. But lightly touching the brake pedal and flying through the windshield doesn't mean the car has great braking performance. It just means it piles all of it's available pressure to the calipers all at once.

There's a reason most of these units come on big trucks and vans. With exception of the SN95 mustangs, almost no performance cars come with hydroboost setups. The only reason they were on the SN95 cars is due to space limitations created by the large modular motors.

Ok,Thanks. That was gonna be my next question, Do you still have it..lol.. Thanks for the replies guys. I did change out both of my power steering pumps to accommodate the Hydra boost units. I also went with the 1.125 master cylinder. I also installed a cooler on my car as I felt the fluid was getting too hot. So far they have been flawless for me.

They make electric hydroboost pumps too by the way.

The type II pumps usually have small reservoirs, and keeping the system cool is important, especially for hydroboost setups. So coolers are important/benefit even more so if you are using hydroboost in a performance app.

Circuit racing or even autocross is really not a good fit for hydroboost. If you push your car on the street, same applies.



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