Radius Arm C-Cap Differences

[SBradley]

I've been going through parts that have been laying around forever and ran across these C-Caps. I don't remember how or where I acquired them, but what I just noticed was that differences in the thicknesses of the bolt bosses between the two. There are no markings on either with the exception of "8" being stamped on the thinner one in two places. Any thoughts on reason for the differences? I was told by reputable fab shop in the area that original C-Caps were actually forgings not castings. I don't know how to tell the difference but the thicker one seems to have a more dense grain. If anyone is interested in one or both, they are available.

 

[mrdrnac]

These are just a guess, so I'll let the experts chime in, but the thicker ones look like F150 caps to me. F150's had a larger bolt size tapped into them for 3/8" bolts instead of 5/16" bolts to hold the coil spring cups. Also Early Broncos had a matched set of caps and that's why they were stamped with numbers. Don't know when they stopped stamping the caps.

 

[SBradley]

mrdrnac, that’s some good info. I wasn’t aware that the spring cup bolt holes differed in size between Broncos and F150s. That could explain it all. When I get a chance, I’ll compare

 

[SBradley]

Well, the mystery continues. Both spring cup bolt holes are 7/16-14.

 

[Apogee]

I think mrdrnac misspoke saying 5/16"...I've only ever seen the 3/8" and 7/16" tapped caps for the spring cups, similarly on the matching radius arms. I just machined my CAGE long arms for the larger hardware, since I was running 7/16" caps and 3/8" arms, that way at least they match and use the same sockets.

As for the variations between the forgings shown, I assume they had more than one manufacturer, or if not, reworked the tooling at some point for the forging dies.

 

[SBradley]

Apogee,

Thanks for the input. That was my Top-of-the-Head suspicion was that the differences were simply the result of manufacturing variances. But that was just my guess so I wanted to tap into the EB brain bank and see what came back. Are you able to confirm that the ones with the larger 7/16 bolt holes were specific to F150? Thanks again.

 

[jamesroney]

mrdrnac, that’s some good info. I wasn’t aware that the spring cup bolt holes differed in size between Broncos and F150s. That could explain it all. When I get a chance, I’ll compare

Early Bronco coil spring plates are secured with 7/16x14 cap screws with 5/8 hex heads.

F100, F150 and 78-79 Bronco use different coil plates, often with 3/8 bolt holes, and different spacing.

Putting F-series caps on Early Bronco Arms (and Bronco caps on F100 arms) creates a situation with mix-matched hole sizes and location

 

[SBradley]

James,

Thanks for the clarification, I had it backwards in my head. So the ones, like these, with the larger bolt holes are definitely EB caps then. That helps, thank you.