Hydroboost

[Gussie]

Hello everyone. I am interested in changing to hydroboost in my 86 k20 which currently is vacuum booster. I was thinking about using a hydrobooster from a 86 k30. Is it as simple as that besides new plumbing and perhaps corresponding pushrod? I see after market kits fir $800 but thought I could piece together cheaper. Thanks

 

[Mr Clean]

If you can find a complete set up it is IMO one of the best things you can do to a Squarebody. What I mean by complete set up is... The Hydroboost, master cylinder, push rod and brake pedel.

 

[Mr Clean]

I paid 55.00 for my last set up. Took me about 40 minutes to pull it from the truck in the salvage yard. If you find one from a SB it is almost a direct replacement.

 

[Strick]

I used the hydroboost from a CUCV when I built my '55 Chevy truck. I love it; the brakes work regardless of how the engine is or is not running. The accumulator on the unit will allow a few stops even after the engine has stopped running. As long as you have all the pieces, the swap is straight-forward. Welcome to the site as well.

HS

 

[Gussie]

Thanks everyone. So the k20 brake pedal is different than a k30 w/ hydroboost? Also, can the stock proportioning valve on my k20 be used which is mounted on the lower front crossmember or does the k30 p. valve which appears to be collated to the M.C. need to be used instead?

I really am having fun on my first big resto...I keep finding little mods here and there to make which makes it more cool. Just getting rear springs on was fulfilling lol

 

[Mr Clean]

The Proportioning valve will be fine if you are staying with drum brakes on the rear. I changed mine out only because I swapped to disc brakes in the rear. The rod on hydroboost has a larger hole on the side that hooks to the pedal. You can use your pedal but you'll have a little play in it.

 

[fast 99]

Try to find one that isn't leaking fluid. They are relatively expensive to replace and are prone to leaks with age.

 

[ross632]

Is the pin for HB and vac in the same location? If not what is the difference between them. Just ordered HB and MC from rock auto but thinking I can make a bushing to take up the slack in pin.

 

[Mr Clean]

Is the pin for HB and vac in the same location? If not what is the difference between them. Just ordered HB and MC from rock auto but thinking I can make a bushing to take up the slack in pin.

Yes the pin is in the same location.

 

[Snoots]

You must be registered for see images attach

 

[SquareRoot]

^^^^Yup. I was gonna say that but I'm glad you beat me too it! Snoots for the kill.

 

[Fabman]

Referencing this thread for the Hydroboost setup...what specifically are you using for a Master cylinder with these hydroboost units?

 

[Frankenchevy]

Referencing this thread for the Hydroboost setup...what specifically are you using for a Master cylinder with these hydroboost units?

Just use a MC from a 1986 K30.

Wasn’t mentioned earlier, but the PS pump also has two returns on HB equipped trucks. Not sure if the pump output is different between HB and non-HB trucks though.

 

[Fabman]

Just use a MC from a 1986 K30.

Wasn’t mentioned earlier, but the PS pump also has two returns on HB equipped trucks. Not sure if the pump output is different between HB and non-HB trucks though.

Ok...is the 1986 K30 disc brakes front AND back? or disc / drum? based on a 1.31 bore size I would think this is for a Disc / drum setup..?

 

[HotWheelsBurban]

Ok...is the 1986 K30 disc brakes front AND back? or disc / drum? based on a 1.31 bore size I would think this is for a Disc / drum setup..?

Yes all square one tons are front discs/rear drums. All GMT400's are too except for the 3500HD which are definitely a different animal than the "regular/normal" one tons. The regular one ton is rated at 10K load but the HD is 15K; they have a solid axle up front with leaf springs and a huge full floating axle in back with massive spring packs. Those are rear discs but they are VERY different than the other 400s. IIRC the 99-06 trucks had rear discs on some years and models, but still had rear drums on others. Newer generations are 4 wheel discs but also require larger wheels and the 8 lug pattern changed around 2010 so the newer ones are all metric specs as well.