Hydroboost Question

[towcat]

You don't need the F450 pedal... you can modify the one you have.

Drill and tap a hole 3/4" higher for a 9/16" NF bolt. That becomes your new stud. Secure the booster pushrod with a nylock nut.

it's already we're wandering into a legal gray area by modifying the brake booster. The drill and retap idea can be done but I wouldn't want to explain to the DOT investigator when something bad happens and your homemade mod was the cause of it. I was there in the early days of the "stuck accelerator" issues Toyota had everything was analyzed many times over.

 

[Pino2234]

I have an 86 and an 85 I want to do the conversion too. So I need an 87-91 brake pedal.

Towcat thats a good way to look at it but I havent decided. But for us who have 80-86 trucks the pedal assembly will not fit in our trucks from an 87 and up. The steering column mount is different. So we have to remove the pedal itself from the assembly and install it in to out 80-86 pedal housing?

 

[agp23109]

Hey everybody,
I got my hands on a hydroboost setup from a 1994 F450 superduty and put in in my 1988 F350. I am happy with the added performance of the braking system. However, the master cylinder from the 450 is of a larger bore than my F350. This, i believe, has caused my brake pedal to be very hard, and has very little travel. I attempted to bolt my stock master to the hydroboost, but the holes for mounting are wider on the new one and my old one doesn't fit. Is there a different master i should be using? I believe my original was a 1 1/8" bore while the 450 one is a 1 5/16" bore. Also the superduty had rear discs with a load-sensitive proportioning valve, and i am running the stock SRW drums. Any help would be greatly appreciated.

Stay with the 1 5/16 master cylinder. I know from experiance. When I did my conversion I modified my 1 1/8 mc so it would work. Although there was an improvement in braking power, I felt there should be more. I just recently installed the 1 5/16 mc and let me say the difference is almost night and day. If I was forced to go back to my 1 1/8 mc I would never tow with my truck again! It makes that much of a difference.

 

[icanfixall]

Definatly stay with the large 1 5/16 master cylinder. The peddle being really high is what you want. Also you now have twice as much hydraulic brake pressure that you have with the vacuum assist 1 1/8 mc. You now have around 2200 lbs of pressure pushing out on the brakes if needed. I really would not "modify" a brake peddle. I was a welder for a large generating station for 30 years. Able to weld anything gas.. Stick or tig and I wont weld a peddle. Thats not jst a piece of stamped metal hanging there. Its a hardened material probably 1 1/4 or 2 1/4 chrome. You can't bend them by stepping ******* them. Might be a need subject matter to find out what they are truely made out of. Sure would be a shock to step down hard and have nothing there. Saying "I'm sorry" when you hurt or kill someone wont get you any points in jail.....

 

[MIDNIGHT RIDER]

This confusion --- at least to me --- about the pedal differences and pedal-pin placement is what has thus far kept me from diving into a hydro-boost conversion on my 1985 F-350.


First, what is the reason for having to move the pivot-pin up --- 3/4" is it ??

Is the hydro-boost actuating rod center higher than that of the factory vacuum-booster ??


If that be the case, could not the whole mess simply be mounted lower on the fire-wall, thus bringing the hydro-boost unit in line with the original rod location ??

I have also read of some that have "angled" the hydro-boost unit and left the original pivot-pin in it's original location.



In short, why must we swap pedals or relocate the pivot-pin ??


Thanks.

 

[MIDNIGHT RIDER]

To test this see where your parking brake sets... If its near the floor or more than 3/4 the way to the floor your rears are way out of adjustment.

I agree 99% with everything else you said.


However, I must point out a wee variance on the parking-brake statement.


There are TWO adjustment points for parking-brake pedal travel; the adjustment of the rear shoes themselves, and a separate cable-length adjustment located along the left frame-rail.


The rear shoes on all my trucks are in proper close adjustment and I purposefully adjust the pedal travel such that full lock-up does not occur until at least 3/4 the way down.

Mechanical advantage is lost when the park-brakes lock with too little pedal travel.



I do highly agree about the silly "self-adjusters".

 

[MIDNIGHT RIDER]

a spacer may be required to insert in the m/c piston bore for the pushrod, if the hydro pushrod is shorter than the vacuum one.

Please describe this spacer; is it simply a round steel disc that resides within the bore ??

it works absolutely beautiful with the GM hydro I run.

From what I read, the Ford hydro units match the vacuum-booster bolt-pattern and are a direct bolt-on.

Does the GM unit's bolt-pattern also match ??

I am assuming this is from a GM pick-up; of what vintage ??

Thanks.

 

[gatorman21218]

Definatly stay with the large 1 5/16 master cylinder. The peddle being really high is what you want. Also you now have twice as much hydraulic brake pressure that you have with the vacuum assist 1 1/8 mc. You now have around 2200 lbs of pressure pushing out on the brakes if needed. I really would not "modify" a brake peddle. I was a welder for a large generating station for 30 years. Able to weld anything gas.. Stick or tig and I wont weld a peddle. Thats not jst a piece of stamped metal hanging there. Its a hardened material probably 1 1/4 or 2 1/4 chrome. You can't bend them by stepping ******* them. Might be a need subject matter to find out what they are truely made out of. Sure would be a shock to step down hard and have nothing there. Saying "I'm sorry" when you hurt or kill someone wont get you any points in jail.....

I modded my brake pedal. And I am not going to argue with you or towcat about the risks involved. However, I will say this about the pedal itself. The factory pin is made up of something harder than carbide. A portaband would not even touch it. However the pedal itself seems to be regular cold rolled steel. It drilled really easily with a step bit.

 

[gatorman21218]

This confusion --- at least to me --- about the pedal differences and pedal-pin placement is what has thus far kept me from diving into a hydro-boost conversion on my 1985 F-350.


First, what is the reason for having to move the pivot-pin up --- 3/4" is it ??

Is the hydro-boost actuating rod center higher than that of the factory vacuum-booster ??


If that be the case, could not the whole mess simply be mounted lower on the fire-wall, thus bringing the hydro-boost unit in line with the original rod location ??

I have also read of some that have "angled" the hydro-boost unit and left the original pivot-pin in it's original location.



In short, why must we swap pedals or relocate the pivot-pin ??


Thanks.

For this reason. If the pushrod is not level with the pin then it can jam up.

 

[RLDSL]

Please describe this spacer; is it simply a round steel disc that resides within the bore ??




From what I read, the Ford hydro units match the vacuum-booster bolt-pattern and are a direct bolt-on.

Does the GM unit's bolt-pattern also match ??

I am assuming this is from a GM pick-up; of what vintage ??

Thanks.

I used a GM unit too off a suburban . It has kind of a funky plate but the holes match up. Have to knock teh studs out and get some longer bolts and a couple of chunks of 2" square tubing for spacers and drill some holes in them to space it out for the pushrod on teh pedal side to match up .
I used the superduty MC and made a slug to slip in between the pushrod end for a spacer . the rod was too short . It all seats down inside the cup of teh MC slug, main pushrod and all so it's not going to get cocked sideways if stomped on.

 

[MIDNIGHT RIDER]

I used a GM unit too off a suburban . It has kind of a funky plate but the holes match up. Have to knock teh studs out and get some longer bolts and a couple of chunks of 2" square tubing for spacers and drill some holes in them to space it out for the pushrod on teh pedal side to match up .
I used the superduty MC and made a slug to slip in between the pushrod end for a spacer . the rod was too short . It all seats down inside the cup of teh MC slug, main pushrod and all so it's not going to get cocked sideways if stomped on.

I sure wish you had a bunch of pictures of this spacer business.

I take it that you were able to use the pin in it's stock location ??


Why did you not utilize the GM master-cylinder ??


Thanks.

 

[RLDSL]

I sure wish you had a bunch of pictures of this spacer business.

I take it that you were able to use the pin in it's stock location ??


Why did you not utilize the GM master-cylinder ??


Thanks.

After spacing it out the pedal lined up. The GM one you have to take a die grinder and smooth out the taper in the eye and square it off and that get's it the proper ID for teh pin on the 92 pedal. ( the hole comes to kind of a V , just grind that off square and it comes out right, not sure about earlier pedals)
The GM MC was a metal top thing with the holes coming out the wrong side I would have had to fabricate a set of adapter lines to reach and it would not have been simple with the tight bends, I would have had to coil it to do it properly. Too much headache, and the MC that was with it was hammared anyway, the new one was dirt cheap and brand new and teh thing stops easier than my 960 volvo now. My wife instantly noticed that I wasn't grabbing the wheel and shoving my foot through the floor at every light anymore

 

[bghnkinf350]

The GM one at least for me, is too big. I put in a 1 9/16 c3500 HD into my GMC and the pedal is pretty stiff. That needed an adapter ring, not sure if it is the same one as mentioned above. If you need the adapter ring though, you will also need the longer studs on the hydroboost.