Hydroboost on GM cars began with the introduction of the 5.7L Oldsmobile diesel engine. My 1981 Bonneville was equipped as such and I found it to be one of the most linear braking systems I'd ever encountered on an automobile. I never experienced any problems with the booster or power steering pump. Everything was still original when I sold it at 267,000 miles.

Now do Fuel Injection.

Hydroboost isn't complex, there isn't much to troubleshoot. Not exactly 'heavy' either. And it's appearance? Subjective. Modern fuel rails on a classic, or a system that's been around since the early 70s? I personally prefer manual brakes, but from where I'm sitting it looks like your dislike of this system has colored your judgement. For a driver, the power assist is tremendous (maybe even overkill) and *that* is what draws folks to it. Different strokes.

I also have owned an 81 Bonneville diesel as well as 3 GM duallies with hydro boost. The complaints I've seen posted here really aren't what I've found in my own vehicles. The cars/trucks that GM has used this system on have pumps designed to operate the brakes and steering, as well as differentely calibrated relief valves, and orficed restrictors to control flow. Plumbing a cooler into the system is about as basic as intalling a transmission cooler.

If you tried to use a conventional power steering pump to power a hydro boost system you will undoubtedly not find it satisfactory. You'll need the whole system, rather than cobbling parts not designed for the purpose together.

I've been down the road trying to use a vacuum assist with big cam, and when I needed the assist is when it would lay down, and I'd end up with both feet planted on the brake pedal.

Done properly the hydro boost system works like it should, but all the pieces need to be in place. As far as trouble with them, and trouble shooting them, complexity, not seeing any of these things in my own cars/trucks, or customer cars/trucks I've worked on. Reliability has to be right up there with a hammer, and an anvil. 3 hoses doesn't confuse me, nor do I consider that complex.

Racing a car with manual steering, brakes, and transmission, just makes the job of driving it harder at speed, that's my experience, having done it...........YMMV

Not sure what I said is worth getting triggered over, I was clear when my comments were preceded with 'My personal opinion', but guess we are in a day & age of intolerance & easily offended. (Was tempted to post a 'Karen' meme).

Heavy, well, that system I sold I shipped, and as I recall it was like 45lbs. That's enough to make any drag racer type wince.

Yes, the assist can be 'over assist', and modulation is near zero.

Not sure how EFI came into the conversation...


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As I stated, a new car that came with it is not a good comparison, because it was all designed to work together.

The complexity comes in trying to get exactly what you touched on, calibration, valving, etc. Troubleshooting comes in when it's not right, calibration or whatever.

Never commented on reliability, but it's a good point. The units are usually sourced from OE applications, so suspect the units themselves are reliable.

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Not triggered. Perfectly calm and rational. Just didn't believe you were giving the Hydroboost a fair shake is all.

And now I know you aren't giving it a fair shake. 17.8lbs. That's what an actual Hydroboost unit weighs. If it's replacing an existing power brake booster, that's an offset of 9.8lbs. Does the car have power steering? If it does there's zero weight increase there. The weight of the hoses are negligible, but if someone has an actual weight... Thus far, this little math exercise says we're looking at a total weight increase of... [drum roll please] eight whole pounds.

To put that into perspective, we're talking about a little more than a gallon of gasoline. For a very noticeable change in braking. Speaking of hardcore drag racers, they hate caliper drag and quick ratio steering, but love pizza cutters and wrinklewalls. I suspect you're really aren't arguing in good faith.

Dude, it's my personal opinion, take it or leave it.

It was a while ago I sold it, I may have been off on the weight, but there are a bunch of different styles, hence, weights. And it included a master.

If I just agree I didn't give it a fair shake, will you stop drilling on this? It's clogging the thread, just move on.


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A lot of good information in everyone's post. And after driving a friend 69 A body with manual disc brakes I've decided to go with Willwood 4 wheels manual disc brakes. With my 15" rally 2s, I'm looking to fit the biggest rotor.

Depending on the inner diameter of the rally ii's I believe you can get a 12" rotor with Wilwood's forged dynalite caliper in there.

Wilwood claims they can fit their FNSL 6 piston caliper in a 15" wheel package, on a 12.19" rotor. If that's the case, I'd absolutely run that package, with a 12.19" rotor in the back with their dynalite 4 piston caliper.

This is their FNSL package. I'd measure this against your rally ii's and see if it'll fit. Shouldn't be any issues with clearing the face of the wheel, possible clearance issues would be with the wheel hoop.

https://wilwood.com/Images/BrakeKits...617_wcd-lg.jpg

I have no problem believing the dynalite calipers will fit inside the 15" rally's, but I don't like that caliper on the front of the car. There's not enough pad area. Keep that kind of deal to lightweight street rods.

FWIW, this post may influence someone else's choice in the future referencing about using a hydroboost system. I just completed a complete brake overhaul on my 1997 K3500 dually, which has hydroboost on it. It's a disc drum system, that has over 250,000 miles on it, so it was long overdue for a rework, and overhaul.

New Power Stop slotted crossdrilled rotors, ceramic brakes, new rear wheel cylinders and HD brake lining. All new hard lines and front brake hoses. The former owner had recently replaced both brake calipers, and they were still in good shape. All new caliper hardware, and bushings. While I was at it, all new lower ball joints, 2 upper control arms, 2 CV axles, hub bearings, and new sway bar pins.

Today I took it out for a shakedown run, and to bed the new linings in, I drove it about 20 miles on secondary roads, and into town where there are traffic signals, so stop, and go traffic. The truck has been out of service for a few months, so I wanted to pay attention as to how the brakes acted from the claim made in this thread that a hydroboosted system isn't proportional.

The claim that hydraulically assisted brakes aren't proportional is pure BS, the brakes work proportionally the same as vacuum assisted brakes work. I really have no idea where the poster was getting information that hydroboosted brake systems are either off, or full on..............:noidea: As I previously posted, I own 3 trucks with hydroboosted systems, each one is very proportional with pedal effort. My next street car project will definitely have 4 wheel disc brakes, as well as a hydroboost system on it.

A Hydroboost system operates at a slightly higher system pressure, and it's simple to change the relief valve in the pump to achieve that increase. It's also nice to have a bit more flow for the increased capacity of the upgrade. If a guy is buying a kit and it doesn't include lines or pump, he's gonna want PTFE hose and a good flowing vintage Saginaw p-pump....so that upgrades "the system". I think there's better (later) pumps out there, but p-pumps are still available everywhere. I used to have a Hydratech system on my '67....but I had disc/drum.

I like the idea of manual operated Wilwood brakes, tho.

The point is not that it doesn't work, or that hydroboost isn't reliable.

The point is that many retrofit operations of these fall short. Many retrofits end up with a mitch-match of parts that cause everything that has been discussed here.

A well engineered OEM system is designed with every part of the hydraulic system in mind, from the pump, to the hydroboost unit, down to the caliper sizing. Comparing how the OEM system on your mid 90's truck performs compared to putting a hydroboost directly on a classic car is not an apples to apples comparison.

Exactly.

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The dynalite calipers are not really an upgrade, the OE 11" disc setup is just as good or better, can even do aggressive pads.

Look at the Kore3 stuff.

https://kore3.com/

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Nothing from Kore3 will fit inside a 15" wheel.

The FSNL setup is good, but not sure it will clear a 15". I know it says 'some 15" ' but I bet it's limited.

Unfortunately, the Kore3 325mm C5/C6 setup needs a 17" wheel I think:

https://kore3.com/proddetail.php?prod=10103-01

But worth calling. Tobin pretty much knows what will and what won't fit in OE apps/wheels. And he is a world of info, firsthand knowledge of all the calipers/setups, incuding wilwood.

He does sell wilwood kits too.


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It's nice to be able to source rotors and calipers locally.

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Having had both the wilwood D52 calipers and currently the FNSL caliper. The D52 is actually taller. If you were going to get either of those calipers on a 12" rotor, inside a 15" wheel, it would be the FNSL.

Looking again, does the OP require it to fit in a 15" wheel? Might be a moot subject.


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Yeah, in post #28 he states he wants to fit the largest rotor he can inside his 15" rally ii's.