hmm...pin location on the hydro boost pedals is usually up about 3/4 inch from vacuum boosted trucks...just saying....
This is true for Ford hydroboost units, however GM ones use a different mounting plate for the firewall and while its stud locations are near-perfect match for the Ford firewall the actual booster may very well sit higher or lower compared to the F-Superduty unit - if it's higher on the firewall then pushrod pin would need to be moved further up the pedal, if the booster sits lower one could possibly get off the hook easy and not move the pin at all - it all depends on what donor truck the GM hydroboost came from. In my case with the '80s 1-ton GM hydro the booster did in fact end up higher on the firewall than the vacuum one, likely in the same general spot as the F-superduty booster, and so I had the following choices:
a) cut the pedal end off the Chevy pushrod and the booster end off the factory ford pushrod, stack the two pushrods on top of each other so the Chevy is on top and Ford on the bottom, slide them in-out till their combined length puts the pedal where I wanted it, then weld them together, thus ending up with an offset pushrod that is the proper length to not need firewall spacers and can utilize factory vacuum-booster pedal as is.
b) move the pushrod pin higher on the pedal (like you did IIRC), then making a firewall spacer to take up the extra length of the Chevy pushrod.
c) space booster away from firewall while tilting it back some to make pushrod length work right while at the same time point said pushrod straight at the factory pedal pin so no alterations in its height are needed.
I went with option c) for simplicity sake and also for ease of locating replacement/spare parts should the need arises - I can grab a hydro from just about any pre-OBS (so mid-70s to mid-80s) fullsize GM truck and bolt it on and go. Of course some boosters provide better assist than others, the boss being IIRC one from a 454-powered 1-ton dually (RPO code JB8), but in my experience with factory-size tires even a booster from a diesel suburban is plenty strong to lock up the four rear wheels on hot and dry pavement despite the 5-6k of weight directly over that axle...
This is great! I have my Chevy setup. and was wondering about the hoses and pump. Especially the pump.
If you manage to find a pump bracket from a diesel van with your engine you could use the GM pump that went with your hydro, or even a better one. I have said bracket, and plan on using it with whatever GM pump has 10k GVW rating or more, and even then there is still choices as far as tank/reservoir setup goes - some have smaller pump tank but with external reservoir above it, some have larger pump tank and two return lines, and IIRC there is even a setup that has both the big tank and the remote reservoir! Do your research, or wait on me to be the guinea pig - your call, however please be aware that my inspiration/motivation to do ANY work on my vehicles is currently beyond non-existent, so it may be quite a while before I get around to finishing this project properly. Also, fwiw, the C2 pump you currently have can be tweaked for somewhat better performance - you'll need the pressure regulator valve and spring (actually just the spring, but swapping them in pairs is easier) from a rack-and-pinion passenger car such as a Fox-body Mustang or a Lincoln Mark 7 LSC to bump up the line pressure, and you can drill the pump discharge fitting port a bit larger for more flow as well.
