Hydroboost Setup with 6bt

[lobie]

Ok so i gotta ask-why in the world does everybody doing a cummins swap switch to hydroboost? Dodge cummins trucks 1989-1998 all used vaccumm assist brakes. 1999 and up i have no idea. Heck if it works for a crew cab 4x4 dually.....? Unless ur running rockwell 2 1/2 ton axles and 44 inch tires, or swapped on huge 4 wheel discs, i'm clueless why you'd spend another $1,000 to stop ur jeep. I've heard complaints about the stock jeep stuff being weak, but after replacing my rubber brake lines with braided stainless, & running the stock brakes and master, with the factory cummins power steering pump/vaccumm pump i almost skipped my daughters head off the dash in a panic stop-man i got an ear-full for that.
And if u swap to hydroboost, how do u run the climate control system that is vaccumm powered?
i'm at a loss.
Ok, now somebody take me to school, lol

It's a much better braking assist system with better technology. Not sure where $1000 came from. If you shop around you can do it for much less. I swapped it in my suburban for around $300. In my jeep its hard to price it as I swapped out the whole drive train. I paid $150 for the 2006 Ford hydro system. I like the hydro boost a lot better. Its not just for towing.

Here's a link you should read and draw your own conclusions.

http://www.pirate4x4.com/tech/billavista/Brakes/#Vancoreview

[TPICherokee]

Ok so i gotta ask-why in the world does everybody doing a cummins swap switch to hydroboost? Dodge cummins trucks 1989-1998 all used vaccumm assist brakes. 1999 and up i have no idea. Heck if it works for a crew cab 4x4 dually.....? Unless ur running rockwell 2 1/2 ton axles and 44 inch tires, or swapped on huge 4 wheel discs, i'm clueless why you'd spend another $1,000 to stop ur jeep. I've heard complaints about the stock jeep stuff being weak, but after replacing my rubber brake lines with braided stainless, & running the stock brakes and master, with the factory cummins power steering pump/vaccumm pump i almost skipped my daughters head off the dash in a panic stop-man i got an ear-full for that.
And if u swap to hydroboost, how do u run the climate control system that is vaccumm powered?
i'm at a loss.
Ok, now somebody take me to school, lol

Ever driven a hydroboost equipped rig? I put it in my M715 -- 4 wheel drum brakes and it stops like a car, it's awesome. I think braking is a spot where I don't mind spending money.

If you run a hydroboost on a Cummins, you still have a vac pump to run the rest of your heater controls...

[Elliott]

Anyone try to use a junkyard unit. it looks as though everyone else is doing it. A used unit cost 50 - 100 bucks.


I was thinking of buying one from a 95 astro and it should bolt right to the stock aluminum block. The astro MC will be used as well.

My big question is..... Why do people install a spacer between the hydroboost and aluminum block. Is this to set the proper rod length to the pedal? Coudl I just cut/sleeve/weld the stock rod to shorten it?

You don't want to weld the HB brake rod as there are two seals inside the HB casting that will cook. I had a guy go through three new hydroboosts that way before he came to me so he had wasted a ton of $.

The '95 Astro makes a good choice, especially the one with the spade shaped rod end (vs round rod end) that has the 5/8" hole you can directly bush down to your 7/16" pedal pin. The other rod end has to be drilled up from 1/2" to 9/16" before you can bush it to 7/16". The rod is 1" too long. If you don't mind air going through the firewall (like on a rock buggy) you can simply use 1" round spacers on the bolts between the firewall block and the flat Astro mounting plate..... or duct tape it to keep the air out Otherwise just take a piece of 1"x1/8 flat stock and bend it around the studs, weld the ends and paint it for your 1" spacer.

Two things I don't like about the Astro units is for whatever reason they get super dirty under the hood and that stuff can cake on there hard which is a real pain to clean up, and then they don't give quite as strong of braking as the 1 ton units. On any used unit you pick up try and determine it is not leaking out the tail of the casting where the rod comes out (a little seepage is normal) or the front of the HB (there is a notch at the bottom where heavy flow can travel).

The reason for seals leaking is usually from old PS fluid/wrong PS fluid and old hose particles that float in the system and turn to shellac on the large internal piston. That shellac can build up and displace the seal. Synthetic PS fluid is thinner and works around seals earlier. All PS fluids are not the same and I recommend a GM part # for fluid about four posts down in my thread in the homegrown vendor section or you can follow more tech at my site www.custompowerbrake.com

Depending on your setup you can conceivably do a complete (used) HB install for under $200 Just remember filters and coolers are the HB's friend and unless you have a two return line system both of those should go in the line between the steering box and the Tee fitting for the HB on the way to the pump so there is no back pressure into the HB.


Now, I guess I should add something in here for the original question. The largest small truck vacuum booster on a gas operated rig will give you a max of about (and I think I am being generous here) 1700 psi at the front caliper if you run the stock cam and have OEM vacuum pressure. Most large disc calipers require 1600 psi as far as I know. Using a one ton hydroboost with the right MC can produce up to 2,800 psi at rpm, or about 2,400 psi at idle. The guy who took this gauge pic for me (at idle) would likely have gotten about 2,600-2,800 at rpm depending on his pump output: Pics are thumbnails


This pic of Stu's TJ with an HB system he put together with a one ton MC/HB was getting 2,600psi at idle so you know he is going to pull 2,800 or more at rpm:


AMC pumps run about 1250 psi and will operate a HB but you can change up the valving to get the 1500 psi most HBs (the ones without the relief valve) are designed for. Also, keep in mind that accumulator is set to take 1500 psi to give you the fullest charge for full power brake pedal applications in the event of a stall or broken belt so if your pump is only putting out 1250 psi you won't have as much back up pressure in the accumulator.
Hope that is all useful info.

[Mikel]

Ok so i gotta ask-why in the world does everybody doing a cummins swap switch to hydroboost? Dodge cummins trucks 1989-1998 all used vaccumm assist brakes. 1999 and up i have no idea. Heck if it works for a crew cab 4x4 dually.....? Unless ur running rockwell 2 1/2 ton axles and 44 inch tires, or swapped on huge 4 wheel discs, i'm clueless why you'd spend another $1,000 to stop ur jeep. I've heard complaints about the stock jeep stuff being weak, but after replacing my rubber brake lines with braided stainless, & running the stock brakes and master, with the factory cummins power steering pump/vaccumm pump i almost skipped my daughters head off the dash in a panic stop-man i got an ear-full for that.
And if u swap to hydroboost, how do u run the climate control system that is vaccumm powered?
i'm at a loss.
Ok, now somebody take me to school, lol

Whatever floats your boat. I have built 3 hydroboost cummins powered FSJs and I couldn't be happier. Cost is closer to $100 using junkyard parts.

Besides, if you use a hydraulic clutch, going with a vacuum booster can be problematic. If you need vacuum for the heater, you can still use the PS/Vac pump most CTD dodges came with.

[poolmike]

Been cruising in my M715 for 5 years with Hydroboost out of a '86 Chevy K30 donor truck. It worked great or so I thought....yesterday I swapped in a 4 wheel disc master cylinder from a '03 Silverado 3500 with a Wilwood adjustable prop valve. What a difference. If I get into the brake pedal, my seatbelt better be fastened or I'll be eating the windshield.

[Elliott]

Been cruising in my M715 for 5 years with Hydroboost out of a '86 Chevy K30 donor truck. It worked great or so I thought....yesterday I swapped in a 4 wheel disc master cylinder from a '03 Silverado 3500 with a Wilwood adjustable prop valve. What a difference. If I get into the brake pedal, my seatbelt better be fastened or I'll be eating the windshield.

That's stepping up to 37mm bore which is 1.45" vs the 1.25" bore you had and it was designed for the largest dual piston calipers they make for light trucks. The stub on that MC should have been too large (at ~1.8") to fit into the bore (~1.63") of the '86 HB though.... it fit? or did you build an adapter and rotate the HB?

[Iceman0502]

Thanks for vclarifying all those items. The spacer is really used to match the length of the rod becuase its not smart to weld on the rod becuase it melts the seal.

Car craft had a article once and the welded a rod, but never mentioned to be careful of the seal.

Just thinking out loud, but instead of adding a spacer on the HB side, are you able to move the mounting location on the pedal side. i havent looked at one in while, but could you weld a tab on the pedal one inch closer to the driver and drive a new hole? Would this throw off the travel of the HB?
I read somewhere that Chevy trucks have a brake pedal for the hydro vs vacum boost. It said the pedal would be much higher if you used HB on a vacum pedal.

[SJTD]

The pedal looks cast to me. I didn't trust welding it. I made a link that moved the pin to the back of the pedal and put the rod on the left side.

This allowed a mount on the front of the firewall 1" thick and moved it about 1-1/2" to the left. My TC is on the left and was too close to the accumulator.

It's from a 2006 Chevy. I did shorten the rod but the weld is near the pedal end and I kept the seal area cold.

[Elliott]

Thanks for vclarifying all those items. The spacer is really used to match the length of the rod becuase its not smart to weld on the rod becuase it melts the seal.

Right, and old seals will handle even less heat. With the Astro HB you have a flat mounting plate so you can simply invert the HB to move the accumulator away from the engine. If you use a different HB I have Astro repro mounting plates on ebay or you can pull one in a yard and then cut/thread the brake rod 3/8-24 for coupling to a shortened rod. Just steer away from the GM truck HBs that have a stepped down rod diameter ~1.5" from the back of the HB casting as you can't thread up that section.

If try to go too short without a spacer you increase the brake rod angle unless you are redrilling the firewall bolt pattern and enlarging the center hole... just extra work over making a 1" spacer and using the aluminum block with the correct 6* angle built in.

What ever HB/rod you use don't put yourself in a situation with the overall rod length where you have to thread further towards the HB casting than the width of a pair of vise grips as any jamb nut up beyond that will strike the casting of the HB before you get full pedal articulation so you shorten the stroke on your MC.

[poolmike]

That's stepping up to 37mm bore which is 1.45" vs the 1.25" bore you had and it was designed for the largest dual piston calipers they make for light trucks. The stub on that MC should have been too large (at ~1.8") to fit into the bore (~1.63") of the '86 HB though.... it fit? or did you build an adapter and rotate the HB?

I rotated the HB when I swapped in the 12 valve. The new master cylinder is a snug fit in the HB, but it went in. Maybe the previous owner of the donor truck swapped in a later model HB? Most of the later model HB's have a shorter pushrod, this one is not. Makes me wonder what it is? Whatever it is, stops the truck!

[Iceman0502]

So this is going to sound stupid, but I will a master cylinder from a 94 dodge ram 2500 work with a Astro van hydroboost.

I'm asking because my donor truck was a 2500 a the mc fits on the booster, but how do I know if whole combination works. The ram 2500 mc should should be equivalent to a Chevy 2500. There are both 1.25" bores.

Does it make sense to use the Ram proportional valve that is attached to the mc? same disc/drum application?

Thanks

[poolmike]

The two units will probably bolt together and work. An adjustable prop valve will be your best bet.