One way to restore bellhousing wishbone bolt bores

[RockHillWill]

There is always the question regarding what to do about front end 'shimmy', etc., and the most common responses are tighten bolts, adjust bearings, set toe-in, rebuild spindles, add rubber around the wishbone 'ball', weld up the ball & grind etc., etc. ALL of which are correct responses, but I have discovered the hard way that these approaches are not guaranteed to fix the problem.

What I discovered at first with the pickup and then with the panel delivery was that while all these items had been addressed, I was still feeling some slight shimmy/shake when test driving. It took me a while to figure out that the issue was in the bell housing where the wishbone pivot housing bolts were quite 'wobbly'. I had to take all the motor stuff out and look until I saw that the problem was the wallowed out holes at the top of the surface where the bolts were held in place by the small diameter cross pin that used to keep the bolts from spinning when tightening the nuts.

There are 13 drawings in the archives for this particular bolt and most of the differences are regarding the shape and depth of the slot in the top of those bolts. The lower edge of these bolts sits on the top of a CAST surface in the bottom of the bell housing. The depth of that counter bore in the bottom of the bell housing and the depth of the slot in the top of the bolt determines the amount of vertical movement of those pins. The slot in the top of the bolts is not a square cut, but rather a tapered cut, so the misfit of the bolt head to the cross pit allows the bolt to not only move up and down, but that tapered slot allows for rotation as well. It should be clear that this will allow the HARDENED pin moving and rotating in a CAST IRON bore to wallow out this hole in the bottom of the bell housing allowing movement regardless of how you fasten/tighten the wishbone pivot ball.

My 'fix' was to build a fixture to hold the bell housing upside down in the mill, machine a pilot to locate the bore in the housing and then replace the pilot with a back spot facer and pulling upward cut a smooth 3/4" diameter deep spot face in the bell housing. After dis-assembling the fixtures, you can use hardened spacers from McMaster-Carr and the pins that you are going to use and set the height of the pins to seat against the bottom of the bolt head slots.

I have done about a dozen of these and it seems to work out real well. I just did the last two of these that I intend to do, as this 'coach building stuff' that I have gotten involved with is taking up most of my time. These fixtures (less the mill collets) are for sale for $200.

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[figment]

Nice to see it done right ! I did use a shim to get the correct height but didn't do anything for the hole diameter. I was lucky that I got by with no shake or shimmy. Thanks for all you do for the Model a hobby ! Norm

[Synchro909]

I've wondered about tapping the bolt holes in the bell housing and making a stud to screw in there. Stud could be locked in by using Loctite or a scotch pin or a number of other ways.

[Rex_A_Lott]

Thanks for showing us your methods. You have a long way to go as a panel beater to match your ability to fix problems.

[RockHillWill]

Barry:
You have a keen sense of the truth, but I plan on working on that. We have finished the Bugatti frame fixture and table, built the first frame, firewall, body outriggers, door jambs, front and rear fender bucks and the grill frame, front motor mounts and it is my plane to get started on some SERIOUS metal shaping to build the aluminum body soon. We are leaving in the morning to take a 1930 Rolls Royce Phantom 1 Town Car to a Concourse DE Elegance show in Keeneland, Kentucky. I will be bringing home at least one of the fender bucks to start with.

I have a left side Model A fender buck already made and I am making a set of wood pieces to build the right side fender as a display for a wood working seminar that I was invited to by a local woodworking club. You could come to Rock Hill and we could practice TOGETHER on that Model A fender, LOL!

Syncro:
I have thought about that as well, and I believe it could be done, but my interest at the time was started by needing to do an 'original' appearing repair. The bore for the .437" diameter wish bone bolts is approximately .470" +/-. I would think that the best way is still not very easy. One is to bore those holes out and either use 1/2" studs, or some how use a 'stepped' down stud. The tops of the studs could be made long enough to cut or mill identical slots in them so that they could the original cross pin. When I thought it thru, I was intending to restore more than one bell housing, and it has turned out to be as I thought, that once the tooling is in hand and the fixture is made, this is not a time consuming project.

NOTE: Both tooling sets have been sold. Thanks!

[katy]

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Stud could be locked in by using Loctite or a scotch pin or a number of other ways.

What's a scotch pin? I googled the term but no joy.

[Rex_A_Lott]

Originally Posted by RockHillWill

You have a keen sense of the truth, but I plan on working on that. We have finished the Bugatti frame fixture and table, built the first frame, firewall, body outriggers, door jambs, front and rear fender bucks and the grill frame, front motor mounts and it is my plane to get started on some SERIOUS metal shaping to build the aluminum body soon. We are leaving in the morning to take a 1930 Rolls Royce Phantom 1 Town Car to a Concourse DE Elegance show in Keeneland, Kentucky. I will be bringing home at least one of the fender bucks to start with.

I have a left side Model A fender buck already made and I am making a set of wood pieces to build the right side fender as a display for a wood working seminar that I was invited to by a local woodworking club. You could come to Rock Hill and we could practice TOGETHER on that Model A fender, LOL!

Sounds like you've been busy. Have a good trip! I look forward to helping you on that Model A fender..."Someday", Thanks for the invite.

[Synchro909]

Originally Posted by RockHillWill

Barry:

Syncro:
I have thought about that as well, and I believe it could be done, but my interest at the time was started by needing to do an 'original' appearing repair. The bore for the .437" diameter wish bone bolts is approximately .470" +/-. I would think that the best way is still not very easy. One is to bore those holes out and either use 1/2" studs, or some how use a 'stepped' down stud. The tops of the studs could be made long enough to cut or mill identical slots in them so that they could the original cross pin. When I thought it thru, I was intending to restore more than one bell housing, and it has turned out to be as I thought, that once the tooling is in hand and the fixture is made, this is not a time consuming project.

NOTE: Both tooling sets have been sold. Thanks!

I was thinking of a stepped stud also. We have been all metric for about 50 years now so having the whole range of metric available as well as imperial, there would be plenty of sizes to choose from 0.47" is 11.94 mm. A 14 x 2 mm thread requires a 12.2 mm pilot hole. (That is only 0.26 mm or in imperial, 0.010" under size)

[Synchro909]

Originally Posted by katy

What's a scotch pin? I googled the term but no joy.

A scotch pin is what I have seen guys on here describe as a way of stopping the ring gear moving on the flywheel. In that application, a hole would be drilled 1/2 in the ring gear and 1/2 in the flywheel. It would be tapped and a screw inserted so that they can't move in relation to each other (flywheel and ring gear, that is)
You guys used different terms for lots of things maybe this is just another. What do you call that?
PM sent too.

[RockHillWill]

Yea, I did not consider using metric when I was thinking about this idea. That might have more possibilities, especially, if it did not have to 'original' looking. If you try that, be sure to post the outcome.

[Synchro909]

Originally Posted by RockHillWill

Yea, I did not consider using metric when I was thinking about this idea. That might have more possibilities, especially, if it did not have to 'original' looking. If you try that, be sure to post the outcome.

Car all running OK at the moment so I won't be doing anything anytime soon. "If it aint broke, don't fix it!!"