Logan
Well-Known Member
I like OEM Upper Control arms to avoid bump stop and BJ rubber boot issues of after market parts so decided to modify stock UCAs to get more caster.
First, I made a jig to hold the arms by the bushing holes and allow the arm to meet a flat plate where I could scribe a circle indicating where the ball joints were located.
Interestingly, I found small BJ arms had more caster than large BJ arms and I wouldn't have to move them as much. Plus, cutting out the smaller BJ threads was cleaner because the old threads would almost be removed entirely. Lastly, if I screwed up a small BJ arm with questionable threads, who'd care, right?
I calculated how much I wanted to move the BJ by assuming the factory setting of +.75 degrees put the adjustments in the 'middle' and I wanted to shoot for +3 degrees- a difference of 2.25 degrees. Reasoning that pushing the upper BJ back would cause it to pivot around the bottom BJ which was 9.5" lower I calculated a movement of .373" 'back'. [or, 9.5 x Tan 2.25 degrees.] This became .266 inches adjusting for the small BJ already being .107" 'back'. Moving the BJ for camber was figured in a similar way with a result that the BJ had to move 'in' .22".
The required movement was laid out on a flat plate and small holes- for increased precision- drilled representing the center of the old BJ location and the new BJ location. The center hole was opened up to 1/4" and a 1-13/16" hole saw used to cut out a 'slug'. A second slug was cut, and the two bolted together. The second slug had a small hole drilled through the first hole to make sure both shugs were exactly the same. The slugs fit perfectly into the old BJ threaded holes with a slight interference. The arm was placed on a level pipe through the bushing holes and the slug's layout scribe marks made level. The slugs were held in place with a dab of epoxy putty then welded in and the offset hole opened up to 1/4" for a 2-1/4" hole saw which removed the added slugs and the old threads almost entirely. A grinder took care of the rest.
I got new threaded 'bungs' from Stock Car Products (904) 232-3500 -the ones that flare out at the top. They had to be cut to 'Mopar length' for the rubber boots to fit right.
I'd like to see how this works but it will be awhile before I do the front of the car. I'll be doing a mini tub and frame stiffeners first...
First, I made a jig to hold the arms by the bushing holes and allow the arm to meet a flat plate where I could scribe a circle indicating where the ball joints were located.
Interestingly, I found small BJ arms had more caster than large BJ arms and I wouldn't have to move them as much. Plus, cutting out the smaller BJ threads was cleaner because the old threads would almost be removed entirely. Lastly, if I screwed up a small BJ arm with questionable threads, who'd care, right?
I calculated how much I wanted to move the BJ by assuming the factory setting of +.75 degrees put the adjustments in the 'middle' and I wanted to shoot for +3 degrees- a difference of 2.25 degrees. Reasoning that pushing the upper BJ back would cause it to pivot around the bottom BJ which was 9.5" lower I calculated a movement of .373" 'back'. [or, 9.5 x Tan 2.25 degrees.] This became .266 inches adjusting for the small BJ already being .107" 'back'. Moving the BJ for camber was figured in a similar way with a result that the BJ had to move 'in' .22".
The required movement was laid out on a flat plate and small holes- for increased precision- drilled representing the center of the old BJ location and the new BJ location. The center hole was opened up to 1/4" and a 1-13/16" hole saw used to cut out a 'slug'. A second slug was cut, and the two bolted together. The second slug had a small hole drilled through the first hole to make sure both shugs were exactly the same. The slugs fit perfectly into the old BJ threaded holes with a slight interference. The arm was placed on a level pipe through the bushing holes and the slug's layout scribe marks made level. The slugs were held in place with a dab of epoxy putty then welded in and the offset hole opened up to 1/4" for a 2-1/4" hole saw which removed the added slugs and the old threads almost entirely. A grinder took care of the rest.
I got new threaded 'bungs' from Stock Car Products (904) 232-3500 -the ones that flare out at the top. They had to be cut to 'Mopar length' for the rubber boots to fit right.
I'd like to see how this works but it will be awhile before I do the front of the car. I'll be doing a mini tub and frame stiffeners first...
