Swapping to hydro boost brakes

[oldwhity]

Recently accuired an 86 k30 with the hydraulic boost setup instead of the vacuum booster. I was thinking about swapping it into my 81 K20. Are they really better? The brakes on the 81 aren't that great now. Would I need to change the steering box and pump too or will mine work? Will it work with the existing pedal assembly? Thanks in advance.

[VileZambonie]

Don't waste your time. Vacuum boosted is the most efficient non power robbing system. Start with your base brake system and do a brake inspection. What is it doing?

[oldwhity]

It feels like it doesn't have enough pressure. It's done this since I got it. I pull a landscaping trailer but even when it's not, it still feels like it struggles to stop. I have to apply more then normal pressure(to me) to stop. Sometimes it feels like there's a fine line between just enough pressure and too much(they will lock). It's real tricky in the rain.

Should I bleed them? Do you think the proportioning valve is having trouble?

[VileZambonie]

Pressure isn't necessarily the issue. Force is what gives you better braking. The purpose of the combination valve is to incorporate a metering valve, proportioning valve and a differential pressure switch in one unit. The metering valve delays the application of the front brakes until enough pressure is created to overcome the force of the brake shoes return springs. This allows equal braking force. The proportioning valve limits the pressure applied to the rear brakes to help avoid wheel lock up since the shoes are self energizing. If it doesn't have a height sensing proportioning valve it will limit the pressure at around 600psi to the rear wheels.

Here's my suggestion, go through the base braking system, check calipers, slides, hoses, shoes (make sure they are installed correctly and hardware is good) The shoes should always be seated on the anchor pin. If they are not, either the parking brake cables are no good or the parking brake is over adjusted. Test the brake booster, pump the pedal until it's firm. With your foot on the pedal start the engine and the pedal should drop significantly.

[oldwhity]

Thanks Vile, I may tear into that next weekend provided I have a day.

So there is no advantage to the other setup? Ive heard others "woo" about it when seen in some of our trucks. If there isn't enough advantage to justify a swap, I may just pull it to sell down the road. Thanks again.

[VileZambonie]

The biggest disadvantages are
#1 it's a drag on the engine where as vacuum power is essentially free.
#2 less hoses that typically leak and are costly to replace.
#3 and the most common problem associated with these hydroboost systems is the morning sickness.

Most people also prefer the pedal feel with vacuum assist.

[oldwhity]

Well, that's enough reason to change my path. Thanks Vile.