Trying to do the old tried and true disc brake conversion on my 71 F100 Short Bed Sport Custom (in sig). Have a 78 F150 donor truck with front discs and everything seems to be in place to rob parts from. Having problems with kingpins. Duh! Well,I've beat on them, heated it all up, beat some more, still can't get them to move. Any ideas? Special tools? Should I take the entire I-beam, spindle and all and take it to the shop to get the kingpins pressed out or would the entire assembly fit on my 71? Just need some direction at this point. Thanks for any help.

 

Probably easiest to take entire axle to machine shop. I don't think they'll swap. IIRC the '78 has a wider track than the '71.
The first time I had to heat mine till they were red before the pins would move. The second time I took the easy (lazy) way out and took the axles to the machine shop and had them do the work (yeah, I'm gettin' lazy in my old age)
While it's all apart are you replacing the king pins? Now is the time to do it. They have two types of bushings, nylon and metal. The nylon won't need to be pressed in or honed to fit the pins but don't last a really long time. The metal ones need to be pressed in and honed to fit the pins but once installed, as long as they are greased regularly, will last virtually forever. Those are the ones I used.

EDIT: I just thought of something. Check the diameter of your king pins. I'm not 100% sure but I think in 1975 they changed the diameter of the pin.
EDIT....again. I checked my spec sheet and it shows the '71 king pin diameter as 0.8592" and a length of 6.353". The '78 is 0.8593" X 6.483". The difference in diameter (.0001") is negligible. The length difference is 0.130" so I'd use pins for the '78 spindle.

 

Correct. 75-79s use slightly longer kingpins.

To the OP, if you are ever thinking of going with a factory front sway bar get the radius arms and C-brackets pictured below... your donor's radius arms may already have the relief for the pin so it's only a matter of getting the C-brackets.. Econolines are reliable donors.

Camper/Trailer Specials and SuperCabs are prime front sway bar donors. Endlink bushings, and frame brackets are available from LMC ('just checked yesterday).

 

I did this swap last winter on a 71. Donor was a 76 f150. I used the entire I beam assembly from the 76. Some will recommend using the radius arms from the 76 as well as they are heavier. I was doing this swap for someone, and he chose to retain his original radius arms. Everything bolted up just fine this way. Here is a quick run down of how I did it:

-Removed radius arms, i beams and coil springs from both vehicles.
-Replaced I beams under the 71 utilizing orginal coil springs and radius arms and beams from the 76
-relocated brake proportioning valve from the 76 to the frame of the 71. (required fabrication of a bracket.)
-Removed the master cylinder from 71, and replaced it with booster and master off the 76.
-Removed brake pedal from 71, welded the hole shut where the master cylinder rod attaches, and drilled a new one so the the master cylinder rod would attach while still allowing the brake pedal to activate the brake light switch properly.
-picked up new hand bendable brake lines, and bent accordingly to attach to both master cylinder and proportioning valve.(wrapping the excess around a full beer, umm I mean soda can provides a nice factory look.)
-Located a vaccuum source and hooked up the booster.
-Bled the entire system, shook hands and gave him the tail light warranty.

Obviously I replaced brake hoses, brake pads, master cyclinder and so forth. I didnt feel there was a lot of play in the king pins, so we didnt opt to replace them. Had it been mine, I probably would have. If I was going to do it again, I would double check the brake pedal assembly to see if it would swap from the 76 to the 71 because once we had everything hooked up, the pedal on the 71 sits a bit high for power brakes, in my opinion. Otherwise it worked like a dream.

 

So how hard is it to get the entire I-Beam assembly off? Looks pretty involved. Keep in mind that the donor truck is still all in one piece, not dissasembled. Do I compress the spring first with a jack before trying to remove that bolt? If so, then what? Or should I start at the other end?

Man, just seems like if I could get that kingpin out, it would save a lot of trouble, cause all I need is the rotor/spindle assembly. But... it ain't like I can drag the whole truck down to NAPA to get the kingpin pressed out!!

 

I don't want to sound like an *** but did you take out the keeper (nut and pin that keeps the king pin in?) Again not trying to be an *** but if you don't know it's there it can be simple to miss.

 

No worries, you don't sound like that at all. I appreciate you mentioning it. But yeah, I did get those out from both sides. Hit them a couple times with a hammer, they wouldn't budge, so heated a little with a small torch, then a couple more whacks with regular hammer and they fell right out.

Kingpins - different story!!

 

Back to Witty73... I already have good power brakes on the 71, so do I need to replace the booster and alter the brake pedal at all, or can I just bolt up the 78 master cylinder to the existing 71 booster and go from there?

 

With the 76 supported properly, I removed the lower shock bolt, and then put some pressure on the coil spring with a floor jack. Next I removed the two bolts that hold the top bracket on the coil spring. Slowly let the pressure off the coil spring. Then removed the large bottom nut and large washer that attaches the coil spring to the radius arm/ ibeam assembly. Now you should be able to pull the spring out of the way. After the spring is out of the way, pull the cup shaped part that serves as the "perch" for the coil spring off the the bolt and you will find another large nut to remove. Once this has been done, you can seperate the radius arm from the I beam. I believe I had to remove the rear nut from the Radius arm where it attaches to the frame, and the bolt from the other side of the I beam where it attaches to the cross member at this time to give yourself enough wiggle room. Either way, if you are going to address the king pins, I believe this is the best process, because you can get them in a press rather then rely on the BFH and heat.

 

Power brakes is good, takes a step out. Chances are though, you will need to swap the master cyclinder because you will need the one with the larger resevoir for the front discs. I do not know if you can just swap the master onto the 71 booster unit, or if you will need to swap the booster as well. Should be able to visually verify if they are the same.

 

Forgive me if I didnt see this as I just skimmed over most of the posts, but why not just swap the complete beams and radius arms with the disks already on them over? The stuff (beams & radius arms - brake lines will obviously be different) bolts right up.

 

Tis much quicker and easier this way,,, unbolt radius arm nuts,,,, unbolt spring holder (two bolts on top of spring cup) ,,, unbolt I-Beams and shocks,, drop entire assembly on floor,,, slide over to new home,,,, reverse process,,,
did this on my 1st,, or maybe my second 66,,,, then you are back on the ground and can fine tune the other stuff.