We’ve all read the stories on how to install the trick, high-dollar suspension components on older cars. However, what attracts far less attention is what alignment settings do you use and where do you go to get the car aligned? In our experience, many production alignment shops don’t want to bother with a hot rod or modified cars. This is likely because the shop can align two stock production cars in the amount of time it takes to achieve a custom alignment with a Pro Touring car.
Another big reason is many shops don’t want to work on a hot rod is that this involves creating custom alignment specs, more in-depth knowledge of alignment settings, and attention to detail that many production shops are not willing to expand. Of course, some shops perform custom alignments. Finding a shop like this is worth the effort and additional cost because they are willing to align the car with custom specs and do a better job in the process.
In this case, the car in question is a ’68 Plymouth GTX with a Magnum Force front coil-over-shock conversion with rack and pinion steering matched with a late model 392 late model Hemi crate engine. The car had been passed around to several shops after the conversion, and the alignment was merely eyeballed and sent on its way. While the engine ran great, it tended to wander dangerously at anything over 30 mph, and a mere glance at the front tires was enough to reinforce the camber settings were not ideal.
Here was a classic situation where money was invested in a quality front suspension, and yet the car was not fun to drive. In fact, it was borderline dangerous with a pull that demanded an effort to keep the car centered on the road. A less experienced performance car fan might immediately blame the custom work and hard parts when all it needed was a professional front end alignment.
The call went out to Cris Gonzalez, owner of JCG Customs in Oxnard, California to schedule a little alignment attention for this machine to make it much more fun to drive. JCG specializes in building complete cars with an emphasis on a track day, autocross, and Pro Touring machines. He recently added a very nice Hunter Hawkeye Elite machine that is capable of precision four-wheel alignment. This is especially critical for sports cars and Pro Touring cars with independent rear suspensions, but is also useful for all cars to indicate if the rear suspension has perhaps suffered damage or just through age is not parallel with the front suspension.
JCG’s alignment specialist Emilio Albor put the car on the rack and began by checking the initial alignment. We’ve listed the as-delivered settings, along with the original 1969 factory specs for this car as well as the final alignment settings. As it rolled in, the camber was set positive, which does not help handling although the caster was close along with the toe. Nevertheless, several important steps were necessary before Albor could add his final settings.
|Angle||Stock 1968||Measured||JCG Spec|
|Camber||+ 0.5 Left
+ 0.25 Right
+ 0.8 Right
|– 0.3 Left
– 0.3 Right
|Caster||+0.75||+ 3.4 Left
+ 4.8 Right
|+ 4.4 Left
+ 4.4 Right
|Toe-in||1/16 per side||0.160” Left
(+) indicates Positive Camber or Caster
(-) indicates Negative Camber or Caster
Many enthusiasts don’t realize that ride height has a significant effect on alignment settings. This demanded first that Albor set the tire pressures on all four corners and then carefully measure the ride height. There are many ways to accomplish this, but JCG measures from the lower edge of the wheel to the top of the wheel opening. Albor discovered the right side was lower by 3/8-inch and since the shocks had only 2 inches of available compression travel, he decided to raise the right side rather than lower the left.
There is a specific procedure to set the front alignment on any car. Camber is always set first. In this case, the initial position found the camber at 1degree positive with the top of the tire angled outward from vertical. To improve handling and limit tire wear for this application, Albor established a ¾-degree negative setting which angles the top of the tire inboard from vertical. To adjust this, Chryslers use an eccentric which move the upper control arm pivot point in or out as required. Once he had the camber set on both sides, that allowed him to then move to the caster settings, which required minimal tuning since they were already very close, arriving at 4.4 degrees positive for both sides.
This left toe-in as the final adjustment. As the GTX rolled in, it had close to 3/8-inch toe-in on the left side with nearly zero on the right. This is where the Hunter machine’s capability to measure from an exact centerline to give individual left and right toe-in specs is a significant advantage. It required several adjustments to not only achieve the proper 0.03-inch toe-in (roughly 1/32-inch) for each side but also to ensure the steering wheel pointed straight ahead.
Albor started the engine several times to help hydraulically center the rack to make sure the wheel would track straight before finalizing the toe setting. He says that if you don’t start the engine and energize the power steering hydraulics, the pump will often later take up slack in the system. This results in the wheel likely not centered which is discovered in the test drive, requiring a second adjustment. Alos, once the steering wheel is centered, this can affect the final toe-in slightly, so Albor went back under the car one last time to finalize everything.
To put the toe-in spec of 0.030-inch into perspective, a 1/32 of an inch equal 0.03125-inch per side for a total toe-in spec of less than 1/16-inch. While this might be on the verge of splitting hairs, it does point out the advantage of using an alignment machine with this kind of precision. Yes, you can do toe-in adjustments yourself on your garage floor with a couple of straightedges and two tape measures, but there are limits to the precision. Unless you measure toe from the centerline of the vehicle, you have no way of knowing what each tire has for the actual toe.
The final check on any alignment is to take the car for a short test drive. Albor told us that sometimes the numbers would be well within spec and yet the car will pull to one side. The quick check for this is to switch the front tires and then drive the car again. Sometimes the tire switch will move the pull to the opposite side, which indicates a problem with the tire. However, he’s also seen issues where the pull is caused not by the alignment but due to brake drag that can be caused by a stuck caliper piston or other brake malady. He also told us that caster numbers that are off could also cause a pull to one side only when the brakes are applied.
The test drive was successful except that Albor felt a very slight pull to the right which he felt might be caused by the tire, so he added 1 psi of pressure to that front tire to slightly reduce the rolling resistance. With that, the GTX was now ready to take on the road with a renewed sense of freeway speed confidence bolstered by the knowledge that the tires are at least now all pointed in the right direction.