Cut springs will get the chassis down and may look cool but it's not going to get you any podium finishes. Throwing big sta-bars on is not going make you an instant open track hero. Adding poly bushings and new shocks is not going get you past that M3 at the next HPDE. Suspension is a system, it must designed and assembled with a vision. You need to sit down and decide what you intend to do and how far you are willing to go to meet those goals. I started with a stock 1968 El Camino chassis. GM decided that the best compromise of handling, comfort, and cost was the tried and proven SLA (short-arm/long-arm) front end design along with a C4L (converging 4-link) in the rear. The SLA works well, when properly designed. The spindle on the early "A" body is much too short, it leads to positive camber gain during bump/roll conditions. The C4L sucks, it requires the stock channel links to bend in order for the design to work properly, not the ideal situation.
Many are going to say "what about the tall spindle conversion I hear so much about," it sucks. Been there, done that. The tall spindle conversion does help correct the camber gain condition but it also results in increasing bump steer to astronomical levels and still leaves FRCH (front roll center height) much too low. It also results in slowing the steering ratio to about 22:1 and increasing the turning circle to about 40 feet, good bye u-turn. To put in perspective my 2000 Chevy work truck with the extra cab option and 33" tires turns a tighter circle.
Do not believe the claims made by the folks of Global West and the like. I have been through their web site doing research for others and have found two truths in their entire site of propaganda: 1) the Negative Roll Pkg does indeed promote negative camber gain during bump/roll through use of a taller spindle. 2) Running shorter upper control arms does aid in the ease of performing alignments should you decide to make the mistake of installing said tall spindles.
The truth about the "tall spindle swap". To truly understand the
tall
spindle swap we first need to understand why some decide to do it. In stock configuration on
the 1st gen Camaro and 1st, 2nd, and 3rd gen "A" bodies the upper control arm
runs from the cross shaft (or pivot) down to the upper ball joint. When the
suspension goes into a roll condition the suspension compresses and the upper
control arm pivot point moves down. If you visualize what is going on you
quickly realize that the upper arm is effectively increasing in length and moves
the upper ball joint pivot point away from the centerline of the vehicle which
increases camber. Since optimum handling occurs when the all of the tires tread
is in contact with the ground, cambering positive away from the centerline
significantly hurts this process as the outer most part of the tire is now the
only portion in contact with the road.
Adding the
tall
spindles corrects this by
keeping the upper ball joint at or above the pivot point of the control arm
shortening the effective length of the arm in bump, it also changes a few other suspension geometry factors by
design. The steering arm is relocated up and forward by quite a bit. This
relocation changes the steering linkage geometry so drastically that it actually
affects the steering ratio, bump steer, and turning circle. Turns that used to
require minimal input from the steering wheel now will require actual movement
of the hand placement on the wheel. U-turns become a thing of the past and
counter steering is now a real chore, this is assuming you are using a
smaller/sportier steering wheel. With the stock bus style wheel forget about any
sort of control at all. Many claim it doesn’t bother them that much but I can
tell you from 1st hand experience it sucks on a race track to have to
reposition your hands for small direction changes when you should be
concentrating on your line or other vehicles in close proximity.
Bump steer is the least annoying but most dangerous of the side affects.
Although you won't experience it everyday while putting around town, when you do
have to deal with it you won't like it. Bump steer is when the length of the tie
rods changes throughout the wheel travel changing the toe-in/toe-out. The
tall
spindle swap typically results in about 3/8" of toe change throughout the wheel
motion. This may not seem like a lot but going from 1/8" in to 1/4" out will
definitely get your attention at freeway speeds
What is the point of all this? The point is that there are many alternatives
that do not have the negative side affects. There are many other
spindles available that do not change the steering geometry. There
also some extended length ball joints and ball joint spacers that will
effectively increase the length of the spindle.
I should point out that there are some out there marketing kits to "fix" bump
steer in the
tall spindle swap
applications. This is not possible, there is nothing you can buy/do/make to
change the steering arm on a cast spindle (safely). Do not get suckered in to
buying the bump steer adjuster kits. The only true “fix” would be to relocate
the steering box and idler arms as well as obtaining a different length center
link to match the new steering arm length/height.
Now that the steering issues are out of the way the last negative side affect is that FRCH is still too low. Most" A” bodies will come in around -3” with the tall spindle and ~1.5” drop spring (typical drop for those going through the trouble of a tall spindle swap). Ideal FRCH is closer to 3" give or take an inch.
So what's the fix? There is a small company out there called ATS, located in Las Vegas, NV. This pioneering company has developed a spindle that uses mostly off the shelf replacement parts and comes very close to "fixing" all of the ailments of the SLA for the early "A" body/"F" body applications. The other fix, which provides better results in my opinion but requires a great deal of sourced parts not easily available for replacement and necessitates at least 17" wheels is using circle track parts. The cost is about equal but the amount of work quite substantial, only an option for the true track fiend.
Since we are talking about steering I guess a few words about steering gear are in order. The best possible replacement box is the newer Delphi 800 series box. Unfortunately I don't know of a wrecking yard option here. New boxes built to be a direct replacement for the "A" body run about 500.00 but provide the best feel as well as a tight steering ratio (12.7:1) and lightweight. Next on the list would be the wrecking yard option of using a 1992-1999 Jeep Grand Cherokee or late model Caprice steering box, again the 12.7:1 ratio and decent feel but without the rack and pinion style mechanics. Lastly is having your stock gear box rebuilt by someone who knows what they are doing and having the valving turned up a bit to improve feel, some even have the experience required to swap guts from a tighter ratio box and give you that 3 turn lock-to-lock that is so highly desired.
Lastly, be careful in believing testimonials. I have found another interesting phenomenon about tall spindles; the owners of said vehicles have the odd tendency to deny reason and insist they work well. Maybe as a result of all the work and expense already invested, or maybe it’s something else. For real word of mouth, look for someone who had tall spindles and now does not. Ask them how they feel about them.
For the rear I have done all the research that can be done, my current configuration is about as good as stock mounting locations are going to get you. I will at some point in the near future have a fully functional 3-link/PHB arrangement but in the meantime this works OK. Replacing the rear axle bushings with the Wolfe spherical bearing eliminates one source of bind. I also replaced the lower links with 19" swedged tubing and 3/4" rod ends. For upper links I am running Edlebrock pieces, they utilize a spherical bearing floating in a polyurethane receiver to limit the amount of NVH transferred to the chassis. Many will say "what about just replacing the bushings with polyurethane or polygraphite", don't do it. The upper link must rotate and articulate simultaneously for the rear end to move up/down. If you run poly bushings and eliminate what little deflection was there before you remove one of the two necessary actions for proper suspension travel. Running all solid mounts completely eliminates the links from "growing", something that they need to do in bump/roll but having all bearings helps to negate the need for arm growth. Lost yet?? OK, the axle moves up and down and the upper arm SHOULD just move up and down also. Instead, it must rotate within it's mount because of the converging angle it is mounted at. This works because the upper links are made of very thin channel steel and used rubber mounts. These rubber mounts and channel links articulate quite well, they shouldn't but they do. Running bearings instead helps but you still run into kinematics issues.
Here are the current corner weights:
LF-908 RF-880
LR-744 RR-708
those who think the El Camino is light in the back would be surprised.
If you made it this far than click me to see how I fixed the madness.