Is my lower control arm toast? With Pictures!
Well in my stuck in the '60's way of thinking, I would only use the alternatives strictly FOR drag racing or autocross/road racing. Stiffer bushings with less deflection are tailor-made FOR drag racing. I have run polyurethane on a purely street driven car a couple times and have eventually experienced noise issues, even with using the manufacturers lubricant. ANNOYING on the street ! Sway bar bushings would be the only exception for me. Just my old *** '60:s opinion.
Properly installed and lubricated poly bushings don't squeak. Run them for tens of thousands of miles, no issues. Best solution for this is a greaseable LCA pin that was designed for use with poly bushings. The factory pin tolerances suck, the inner bushing shells are worse, using stock pins and shells with aftermarket bushings requires checking and correcting the tolerances to be successful.
I vote for the rubber bushings as well. Street cars hit pot holes etc. I'd rather have the rubber bushings absorb some of that energy instead of transferring it to the K-frame. Many reports of bushings without sleeves letting the control arm move around. Then you get adjustable strut rods to crank the bushing back into a bind to keep things in place. I'm with the others. Sometimes better to leave the race track parts for the race track. With a sleeved bushing deburr and run it.
If your LCA's move around with poly bushings, the installation was incorrect. If there's a bind in your LCA's with poly bushings, your installation was incorrect.
The "problem" with poly bushings isn't the bushings, it's the lousy factory tolerances- and the installer. People slap them in and use them with incorrect tolerances and expect them to work because they don't understand how they work. They're different than the factory rubber bushings, they install differently, and the tolerances are MUCH more important. They have to fit tightly in the outer shells (if they use the original shells), the pins have to fit tightly in the bushings. Then, the strut rods have to be the right length for the new bushings. The factory parts all
depend on the slop in the rubber bushings to get away with the tolerances not being exact. The poly bushings remove the slop, so, the tolerances have to be corrected if you want everything to work properly. Simple as that. They aren't stock bushings, they don't work like stock bushings.
Why these 2 bushing aren't the same fit would puzzle me. While I have no experience in aftermarket plastic bushings, I had assumed they were all slip fit, no press req'd.
It's no puzzle at all, the factory pin diameters are all over the place. I measured 4 different sets of factory LCA pins and found like 6 different diameters, and they weren't close. The range was from .928 all the way up to .945". Factory tolerances sucked.
The Delrin bushings, on the other hand, have very precise tolerances. The fit on the Delrin bushings should be a light press, or tight slip fit. I used a press to install the Delrin bushings in my Qa1 LCA's, but it was a pretty light press. The press was just the easiest way to do the install smoothly. The pins were a tight slip fit, I tapped the LCA's with bushings installed onto the pins with a dead-blow hammer. They don't just slide on and off loosely. I found the LCA's still moved smoothly though, much more predictably than with rubber bushings depending on the elasticity of the rubber to allow the LCA travel.
For the OP- I would find a new LCA for use with Delrin bushings. You can probably smooth that one out, but stock LCA's are cheap and plentiful if you don't need a set with sway bar tabs. And you can buy sway bar tabs from Peter, so, there's really no need to mess that that LCA. The Delrin bushing may spin some in the LCA. On my install I think the pin would probably be where the movement occurred, but that may not always be the case because the fit of the bushing in the LCA and the fit of the pin in the bushing is pretty similar, so some movement may occur at both spots.
As for the pins, I would make sure you have the same fit on both bushings. If you don't, I would look for different pins. As I mentioned above, the tolerances on the factory pins aren't great. They're actually pretty bad for what they are, I mean, .928" all the way to .945"?! That's not close. I used a set of Firm Feel greasable pins with my Delrin bushings. They fit great, and both sides were the same. You don't need the greasable aspect of them because the Delrin is self lubricating, but the tolerances are much better. And since they're designed for poly bushings, the diameter is correct without using an inner shell. So, no old bushing shells with lousy tolerances needed at all. The tolerances have to be right, there's no slop like with the rubber bushings to make up for bad tolerances.
Also, the QA1 arms come with rubber bushings installed. I don't know why such a great part comes with crappy factory style bushings, but they do. Just FYI if you do buy the Qa1 LCA's, you'd need to remove the rubber bushings and outer shell to run the Delrin bushings. Which is exactly what I did with mine. You can see my installation of the Delrin bushings in my build thread, decent amount of pictures, etc.
My "new" '74 Duster- or why I need a project like a hole in the head
