Reparing a cheezy fix for a '55 PS idler arm bracket

[dmsfrr]

I was under my dusty project car looking to put the passenger side steady rest back in after reinstalling the engine and noticed the bolt up thru the idler arm bracket into the frame was missing.
The nut inside the frame had pulled thru years ago and someone "fixed" it with a (now broken) tack weld. There are no access holes in the frame anywhere close to this.

Any suggestions on how it can be fixed now?

I'm considering removing a piece from the lower outside edge of the frame (4th photo, yellow lines)
then tack welding a washer & replacement nut to the top side of the damaged bolt hole, and welding the repaired piece back in place.

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[bobss396]

The bracket is most likely cast or forged steel, tricky as you can see to weld to the chassis.

Possibly fixes:

#1: Open a large enough hole next to the mounting hole to allow a steel plate to be inserted, something like 1" wide x at least 1/4" thick tool steel (anything above 1018 CRS too) would be okay. Drill and tap for the correct mounting bolt. Drill a 3/8" hole either side of the mounting hole, maybe 1" to each side through the chassis. Insert and hold the strap in place with a bolt where you want it, rosette weld through the 3/8" holes. Weld a plate over the access hole. Lay it out on paper first, I have little sense of the actual scale.

#2: Make a new bracket out of steel bar. Got any 4130 alloy laying around? I would replicate the bracket in steel but give it some mounting ears that can be welded to the chassis, it should hold well. If you don't have the abilities you'll have to have someone copy and make the bracket, possibly a 2-3 hour effort by any decent shop.

 

[frank long island]

you could use a nutsert/ rivnut looks like a rivet with threads but you need a special tool to install them

 

[Dominic Hide]

You can buy the correct "idler arm crush nut" from any Thunderbird parts store. Concours Parts has it listed for $8.19. Part #3a351

 

[dmsfrr]

You can buy the correct "idler arm crush nut" from any Thunderbird parts store. Concours Parts has it listed for $8.19. Part #3a351

http://www.parts123.com/parts123/yb...~S4RE18VXC673268419232a~Z5Z5Z5~Z5Z5Z50000051c

Ok thanks, I see that part but I'm a bit concerned that the shoulder will keep the cast bracket from sitting flat on the bottom of the frame and allow it to rock slightly.
Maybe putting a thin spacer between the bracket & frame would help distribute the stress of the bracket trying to twist from the stress on the idler arm.
It might be why the old nut pulled thru. Note the space at the top of the bracket in the photo, caused by the edges of the hole being bent downward.
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[bobss396]

Most likely, the old nut pulled through because the bracket was loose. Looking at this picture, a flat spacer should work for you and be a lot simpler to make.

You may be able to also insert a shouldered nut into the hole (grind the hole open if needed) and have it TIG welded in place, then it would be very strong and the spacer will be fine. I'd think the spacer could be as thick as 1/8" and be okay.

I like Frank's idea of a riv-nut, we use them quite a bit at work, but to get a pull on that size and be retained in steel takes a special puller. We do them in aluminum (5/16-24 thread) and that takes a pressure approaching 600 PSI.