I'm looking at converting my vac. brake booster to a hydro boost system using a unit from a 93' C3500 truck. Does anyone know if the firewall mounting holes, M/C mounting bolts, and clevis pin mounting are all standard on these units, or whether there are mods required to fit the C3?

 

i think there are old posts on this

 

www.hydroboost.com

 

If I remember right that is the same unit Noval is running on his car
should find lots in the achives

Steve

 

I think most of the archives are still missing but there are these two posts by Norval.

"I have bought 2 different systems and both times the units worked great . The first was from a 85 van and it cost $50 complete. I used it for a year then decided to try one from something larger. It was from a 94 one ton truck and cost again $50 , same yard. It bolted in place of the other unit and just has a larger internal bore.
The units are almost a complete bolt in. The rod needs to be cut off and rethreaded to 3/8's coarse of fine, can't remember and the stock clevis end can be reinstalled. The 4 holes in the firewall are already there. I turn the mounting plate around to move the nitrogen canister away from the motor and the lines down under the unit but this is effortless to rotate the plate. A little file work is need on the center where it passes through the fiberglass but that is just a little clean up work. A stock power master cylinder from a vet works perfectly or the non power master needs it's piston modified.
The 4 studs that come with the unit are pressed into the firewall to make future installations and removals easy. The holes are already the right size.
I was first on here to start pushing these units, I found them to be almost a bolt in, plentiful around here, cheap and the wreching yard own said there is not a great call for them.
I would definitly recommend them to anyone who wants a very compact powerful system. As far as matching components up to a system i have had 2 different units and both work flawless.
They are far stronger then vacuum systems and compact too."

"I have been running this system for 2 years now and really like the system. I had manual brakes before that required too much pedal effort. The first unit was from a 83 1/2 ton and it worked great. I then got the idea to go with a larger unit from a 94 one ton. To me the units are identical although the operator of the wrecking yard said the internal bore would be greater in the one ton.
As for installation I found the 4 mounting holes already in the fire wall. I used the 4 supplied studs and installed them in the firewall. Didn't even have to redrill the holes. They pressed right in using a large nut , washer and proper nut. The center hole did require slight fileing to fit. I also turned the mouning plate around by loosening the large nut and turn the mounting plate 180 degrees. This is after filling the little tit off and filing another 1/2 round in
The stock power master bolts right up without problems or the old non master requires the hole to be filled in which is too deep. Be careful filling this hole in.
The units are very reliable, very expensive if bought new, cheap in the wrecking yards and hardly every cause problems.
The units in the 80's and 90 are identical and fit. Why try something else if these work
My pedal effort has gone way down and the braking force way up.
The unit is extremely compact and makes changing the last plug even in a big block with tall valve covers easy."

 

Thanks all for the help. I did check the archived messages, and had gained some confidence through that info. Also contacted NORVAL, and obtained a little more private tutoring on the matter. I've now purchased a new unit and will be doing the upgrade soon. Got a detailed step by step conversion originally posted by 71'AirStrike back in Sept. 2002. I think I can actually clearly understand the whole procedure now. Don't look forward to removing the Vacuum booster, but will struggle through it for the expected improvement.

Yellovette

 

My unit is from a 94 one ton and it was identical to an older 83 1/2 ton. The mounting plate on both units were the same. The linkage on all the units in not right. It is too long but you just cut it off, run a 3/8th die over the rod and use the stock clevis pin.
I do rotate the mouting plate 180 degrees to put the hoses on the underside. I also take the 4 studs that come in the plate, remove them and put them in the firewall. It really makes for easier installation and future removal really easy. The holes in the firewall are already the right size for these studs.
It is really a simple swap.