K member swap and upgrades. Bergman pins
I find your comment funny there were no issues with the k member you state there must have been a issue prior and they should withstand 150ft lbs then why are you beefing yours up if it will withstand that
Simple, I didn't gusset the LCA pivot tubes to withstand the torque applied to the pins.
The entire corner weight of the car is supported by two things on a torsion bar car - the LCA pivot pin in the K frame and the torsion bar anchor in the transmission crossmember. The corner weight on these cars is in the range of 800 lbs give or take a bit, which means that just sitting on the suspension the LCA pivot (and therefore the K frame and pivot tube) is probably holding ~400 lbs of force. And that's before the suspension moves.
On a car with factory torsion bars, the wheel rate is about 100 lbs/in, with about 2.5" of compression travel possible, so, add another 250 lbs to split between the LCA and the anchor. On MY car, with 300 lb/in bars and the same 2.5" of compression travel, add another 700 lbs of force to split between the two. And of course if the suspension bottoms out more force than that can be applied in both cases.
So, yeah, the torque on the pins only applies a minimal load to the K frame compared to what it has to carry with the suspension loads. So if a 150 ft/lb torque caused the pivot tube/K frame to crack, well, it's probably a good thing it happened then because it probably would have failed later anyway when the suspension was loaded. Or worse, when someone was out driving.
And the wildcard is the factory welding, which was all over for quality. Some K frames have really terrible factory welding, so, those welds can crack if they weren't done properly. If everything is in good condition then the 150 ft/lb torque shouldn't be an issue. But not all 50+ year old K frames are in good condition, so they need to be checked. And if you build your car with better tires and stiffer suspension than the factory did, well, you should plan on having more force exerted on the K frame and torsion bar crossmember than the factory did. So gusseting the K frame is just good practice IMHO. Either way, if a 150 ft/lb torque cracked the welds, the pivot tube or the K member, well, it needed repair anyway, since it would never have withstood the suspension forces which will be much higher.
