Drum vs disc lower ball joint question

[4spdragtop]

What are the differences between the 2? I'm talking small bolt pattern.
Heres a pic of 2 Lbj's.
Top one I believe is disc, bottom for sure is drum.
The one difference that I know of was mentioned in an earlier thread is the hole diameter for the 1/2" mounting bolts is slight larger on disc break Lbj's.
If that is the only difference why cant the holes simply be enlarged slightly and function the same?
Thanks
Steve

 

[hemi71x]

Drilling the bolt holes out to 9/16 inch is commonly done when doing a Kelsey Hayes, 4 piston caliper disc brake conversion.

 

[4spdragtop]

So you can order a pair of drum brake Lbj's, drill them to 9/16" and be good for the factory KH? Thanks Jim!

Drilling the bolt holes out to 9/16 inch is commonly done when doing a Kelsey Hayes, 4 piston caliper disc brake conversion.

 

[RustyRatRod]

So you can order a pair of drum brake Lbj's, drill them to 9/16" and be good for the factory KH? Thanks Jim!

That's what it sounds like he said. I never knew that.

 

[72bluNblu]

Jim can clarify but I think that only applies to a certain year range/model of lower ball joint.

 

[RustyRatRod]

Jim can clarify but I think that only applies to a certain year range/model of lower ball joint.

I "assumed" we were talkin about the early 4 piston caliper A bodies. Course you know how dangerous assumin is. lol

 

[72bluNblu]

I "assumed" we were talkin about the early 4 piston caliper A bodies. Course you know how dangerous assumin is. lol

No it's definitely only true for the KH disk lower ball joints, the 73+ disk spindles use a different bolt spacing. But I think the 73+ drums spindles do too.

I think the only ones you can just drill are the 67-72 10" drum lower ball joints and that only works for the KH disks. But like I said, Jim would know better than me as I don't deal much with the SBP stuff.

 

[RustyRatRod]

No it's definitely only true for the KH disk lower ball joints, the 73+ disk spindles use a different bolt spacing. But I think the 73+ drums spindles do too.

I think the only ones you can just drill are the 67-72 10" drum lower ball joints and that only works for the KH disks. But like I said, Jim would know better than me as I don't deal much with the SBP stuff.

No doubt. He's knocked a ton of this stuff apart for a long dang time.

 

[4spdragtop]

For my situation its 2nd gen cudas(sbp).
Anyone got pics for reference of 73+ LBJ'S?? Both drum and disc.
Thanks guys!
@hemi71x

 

[72bluNblu]

For my situation its 2nd gen cudas(sbp).
Anyone got pics for reference of 73+ LBJ'S?? Both drum and disc.
Thanks guys!
@hemi71x

This might clear things up, I was just posting the full list over on the Big Block Dart thread. This doesn't confirm the spacing but I know it's different for 73+ compared to 65-72. The 73+ lowers were the same regardless of drum vs disk.

It also shows I was wrong about the earlier drum lowers, they should be the same 65-72. And we already have confirmation that the difference in the earlier ones between the drum and KH disk was the bolt size.