hydroboost or rear disc

[tbrumm]

Okay, I had a few minutes to get under the dash with a flashlight and tape measure tonight. From the centerline of the vacuum booster pushrod to the centerline of the lower mounting studs is 1-1/4 inches. On the hydrobooster, the distance between the centerline of the pushrod to the centerline of the lower mounting studs is 2 inches. There is that 3/4inch we are talking about! So, if I am thinking of this correctly, the vaccum and hydro booster both use the the same 4 mounting stud configuration to bolt up to the same exact location on the firewall, BUT the hydrobooster pushrod centerline is 3/4 inch "higher" (because that is just the way the darn thing is made) than the vacuum booster pushrod centerline. Here I was giving the engineers some credit for actually providing a little extra leverage to the vacuum booster based on the pin location. In actuality, the two different pin locations appear to result from the simple need to adapt two different types of boosters to both fit in the same truck in the same location. Oh, its great when the clouds clear and the light shines through! Thank you to all of you have who added your knowledge and experience to this discussion. I am very glad this pin location difference was brought up (yet again) so I had the opportunity find out about it before I started my install. My search for the FSuperduty pedal will continue!

 

[LCAM-01XA]

Or you can just get a hydroboost unit out of a cheby suburban , then all you have to do is make some 2" spacer blocks to mount the booster out away from the firewall and some long bolts and it hooks right up without a fuss. No other modifications needed, at least on an OBS
Did have to cut a short jack shaft to fit in between the booster and the superduty MC to take up a gap, the rod coming out of the booster was a tad short which led to a low pedal , but that was easily solved,

Well ideally you wanna bring the booster down a little too, but those extra 2" length in pushrod make the Chevy unit a whole lot more tolerant of less-than-perfect alignment w/ pedal pin than Ford units are. Also, ideally you probably want a booster from a 1-ton DRW truck w/ 454 big block, those had the largest GVW and thus required the strongest brakes. The suburban/blazer/halfton booster looks and fits the same, but is in fact a different unit from those used on the smaller trucks. In reality it probably don't matter much tho, I had an '80s Suburban booster stopping my idi brick about as good as the '00 C3500 booster that stops it now.

Okay, I had a few minutes to get under the dash with a flashlight and tape measure tonight. From the centerline of the vacuum booster pushrod to the centerline of the lower mounting studs is 1-1/4 inches. On the hydrobooster, the distance between the centerline of the pushrod to the centerline of the lower mounting studs is 2 inches. There is that 3/4inch we are talking about! So, if I am thinking of this correctly, the vaccum and hydro booster both use the the same 4 mounting stud configuration to bolt up to the same exact location on the firewall, BUT the hydrobooster pushrod centerline is 3/4 inch "higher" (because that is just the way the darn thing is made) than the vacuum booster pushrod centerline.

OK, so no need for me to play underdash ninja again, you got your own measurements, and they certainly show the need for moving pedal pin higher. By the way the booster mounting plate is removable, you can swap in w/ one from a GM truck if you wanted. So it's not that the booster fits only one way and that required different pedal, it was deliberately positioned by the engineers higher than the vacuum unit. I suspect it has something to do w/ leveraging on the larger bore master cylinder demanded by the big calipers all around...

 

[tbrumm]

So I am still trying to find a brake pedal assembly from a 92-97 OBS F-Superduty for my hydroboost conversion. I haven't had a chance to hit the salvage yards and search yet. But, I did find a local guy on CL that is parting out a 1989 F-Supeduty. Would the brake pedal assembly be the same between the OBS and Brick?? Thanks.

 

[Vegas-Misfit]

If it has hydro boost it should be the same pedal... If not... Then your search continues :/

 

[tbrumm]

You must be registered for see images attach

I pulled this brake pedal assembly out of a Brick 1989 F-Superduty with hydroboost. I should have measured (measure twice-unbolt once!), but the pin on the Brick pedal is too low to work with the hydroboost in the OBS. Anybody need a brake pedal assembly from a hydroboost Brick F-Superduty?

 

[Vegas-Misfit]

If I wouldn't of got a pedal assembly already lol

 

[riotwarrior]

Just take YOUR Brake pedal, grind the weld off back side of PIN, measure up accordingly, drill new hole, and install pin, Have pin welded and then get a bolt that fits the old hole, Grade 5 or 8, make it just a PLUG for filler for hole flush to arm both sides, weld it up in place VOILA done like DIRTY DEEDS DONE DIRT CHEAP....insert song into head now....

JM2CW

Al

 

[jlwoods99]

Lets revive this , did you finish this project ( with pics ) I'm thinking of doing this.

jim

 

[tbrumm]

http://www.oilburners.net/forums/showthread.php?63819-Holy-stopping-power-Batman!!!-Hydroboost-installed!
Jim, I did complete the hydroboost swap and it is really worth the effort! Here is my other thread that has some pics.

 

[icanfixall]

If your going to grind and weld in a pin to the hard material brake peddle please find out what material the peddle is. I'm thinking you will need 8018 or 9018 stick rod to make a quality weld bead on that hard metal peddle.

 

[eastsideauto]

id like to do hydro boost and maybe throw in a dodge dana 80 with discs or a AAM 11.25 axle w/ disc

That is what I am looking at doing, after the HB conversion, of course.

 

[LCAM-01XA]

If your going to grind and weld in a pin to the hard material brake peddle please find out what material the peddle is. I'm thinking you will need 8018 or 9018 stick rod to make a quality weld bead on that hard metal peddle.

Well this is somewhat interesting, I know the pedal arm is supposed to be all sorts of hardened and what not, yet cheap 1/8" bits from Harbor Freight go thru it like butter, turned by a cordless drill and without any cutting lube too. No bits were broken or even dulled in the process either... And it's not like the bits are of super high quality, I've killed plenty of them running thru stainless plates and grade-8 hardware... Honestly the pedal arm material behaved very much like regular mild steel and nothing like the heavy-duty hardcore stuff it's supposed to be. Go figure!

 

[BrandonMag]

Well this is somewhat interesting, I know the pedal arm is supposed to be all sorts of hardened and what not, yet cheap 1/8" bits from Harbor Freight go thru it like butter, turned by a cordless drill and without any cutting lube too. No bits were broken or even dulled in the process either... And it's not like the bits are of super high quality, I've killed plenty of them running thru stainless plates and grade-8 hardware... Honestly the pedal arm material behaved very much like regular mild steel and nothing like the heavy-duty hardcore stuff it's supposed to be. Go figure!

Wow... That is contrary to everything I've read about the brake pedal. Good information to know!

 

[LCAM-01XA]

I know, I was surprised as heck too! But those cheap bits went right thru the pedal arm, no fuss at all, in one side and out the other in no time. I was like ***, that ain't what I expected

Some time in the near future I wanna see how it responds to MIG welding, I got the gut feeling the setup I use for heavy bumpers and frames will wok out quite well there...

 

[79jasper]

also going up one size on the rear wheel cylinders will make a world of differencemaster.

Do you have a link or anything for more info on this?

the ambulance grade on the back

I haven't seen an option for the ambulance package when buying brakes. Do you have any part numbers?