Want fat rubber in your A-Body?...
Want fat rubber in your A-Body? Be aware that the tire will be hard-up against the leaf spring before the full width of the wheelwell is used. Want more? The Mopar Performance offset hanger and shackle kit, PN P4120077 (hanger) and P4120075 (shackle), is for you. E-Body kits are available as well, PN P4120078 and P4120076.
It's nice to have power, but getting it to the ground is just as important when taking out the guy in the other lane. We've all heard stories of big-power cars turning meek numbers, along with the excuses for getting smoked halfway down the quarter. Burning rubber makes for an impressive show, but getting a car down the track in a timely manner requires hooking. It takes a lot to get a car to hook, and one thing that always helps is more tire.
Most Mopars are endowed with generous wheelwells-some better than others-but with some body styles, you run out of clearance to the suspension before the wheelwell is used up. This is because Mopar mounted the leaf springs to the outside of the framerail. Look at the rear leaf-spring suspension of an A- or E-Body Mopar and you'll see some real estate left between the spring and rail that can be used advantageously.
Mopar racers have long been aware of the clearance to be gained by relocating the leaf springs. Mopar Performance has been producing kits for years for this purpose. Essentially, there are two approaches: Offset the spring as close to the framerail as possible; or, move the spring into the rail. The spring-offset kit will move the spring back in line with the factory inner-wheel tub so the spring is no longer the primary limitation on clearance. It allows the full width of the factory wheelwell to be used. The other approach-moving the spring into the framerail-sets the springs about 3-inches inboard from their factory location. While this moves the spring well out of the way, utilization of the extra space requires either extensive modification of the factory wheelwells ("mini-tubs"), or the fitment of aftermarket "tubs."
The offset shackle moves the...
The offset shackle moves the spring inboard about .850 inch, and bolts directly in place of the originals. Notice that the offset shackles are a little longer than the stockers.
We wanted more tire clearance in our '68 Barracuda, so we considered the options. The spring-in-the-rail package could provide room for massive meats, but "tubbing" the car comes with big compromises on this body style. The fastback body's interior is much like that of a station wagon, and the interior panels are hard-up against the factory wheelhouses. Reworking or "tubbing" the body means modifying or removing the stock interior panels-a compromise of originality we didn't want to make. Also unique to this body style are the folding trunk-divider panel and fold-down rear seat, which we had, although they weren't installed in the car. Once the inner well was widened, we could forget about reinstalling any of these pieces.
Instead of such radical surgery, we opted for the spring offset kit. Although the offset kit wouldn't yield as great a clearance as would be accomplished by moving the springs into the rail and adding tubs, it would add about 3/4 inch of tire clearance to the inside, which is a substantial gain. Best of all, once installed, there are no compromises to the look or structure of the car. The offset spring kit took a weekend to install, and we upgraded to an 8 3/4 rear and polyspring bushings at the same time. Now all we need to do is find some bigger meats to use all that extra space.
The spring-eye bolt location...
The spring-eye bolt location is higher up than the stock location. With the rear shackles being a little longer and the front bracket a little higher, the net effect on ride height is canceled, but the geometric change will increase the suspension's dynamic rise under acceleration, helping to plant the tires.
To move the springs inboard,...
To move the springs inboard, the rearend needs to come out. Our '68 Barracuda came with the light-duty 7 1/4 rear, which we will swap for a beefier 8 3/4 unit. Support the car with jackstands under the rear framerails and lower the rear to allow the suspension to droop.
The offset front-spring hanger...
The offset front-spring hanger moves the edge of the bracket against the framerail. Note the relative position of the bracket's edge versus the mounting bolts. The nut for the spring-eye bolt comes welded to the bracket since there's no room to reach it once the bracket is installed.
To get the rear out, the driveshaft,...
To get the rear out, the driveshaft, brake hose, and parking-brake cables are disconnected.
Next, the shocks are unbolted...
Next, the shocks are unbolted at the lower mounts. Then the shock plates and U-bolts are removed and the rear is ready to come out. Raise the floor jack under the rear to separate it from the springs.
To make way for removing the...
To make way for removing the rear, unbolt the rearspring shackle brackets. Two bolts at the frame are all that hold them in.
With the springs dropped,...
With the springs dropped, the rear can be rolled out the back.
The front-spring hanger bolts...
The front-spring hanger bolts through with four more bolts at the chassis' spring box. Zip those out and the springs are free.
We were reusing the stock...
We were reusing the stock springs, but since they were out, it was a good time to replace the bushings. We used this homemade jackscrew arrangement and 3/4-inch-drive impact wrench to quickly remove the old bushing.
We swapped to polyurethane...
We swapped to polyurethane bushings, which are firmer and give a harder hit off the line than the stock rubber bushings. The poly bushings are an easy hand install. Just lube 'em and slide the two halves in place. A steel tube slides in the center for the bolt.
Since the front hanger bracket...
Since the front hanger bracket will be hard against the framerail, clearance must be made for the spring-eye nut on the backside. There are several ways to cut the clearance. We carved this slot using an aggressive carbide burr in a die grinder. The slotted shape (or a really big hole) is required to allow the bracket's mounting studs to slide into place.
Tucked away in the shop was...
Tucked away in the shop was a fresh A-Body, 8 3/4 rear assembly. We had rebuilt the unit, thinking it may come in handy one day. Inside are new 4.10:1 gears, a new Auburn Sure Grip, Moser hardened big bolt-pattern axles offset for B-Body brakes, and 11x2 1/2-inch drum brakes rebuilt with all new parts.
With the springs prepped and...
With the springs prepped and the new offset pieces installed, we bolted them in place. Notice how the front hanger is right against the rail. Visible is the front of the slot cut to clear the pivot nut.
The spring perches on the...
The spring perches on the rear needed to be relocated to match the new spring position. The rear was supported securely with jackstands under the tubes, and adjusted until level with a screw jack at the pinion nose.
We moved the perches about...
We moved the perches about 11/16 inch per side from the stock location. Measure carefully, keeping the perches at the correct angle and the same distance from each housing end. As a consideration for drag racing, we changed the pinion angle about two degrees further downward.
Next the angle of the original...
Next the angle of the original perches was measured so the replacements could be installed at the same relative angle to the pinion.
We did notice that the perches...
We did notice that the perches had a larger center hole than the pilot size at the leaf springs' center bolts. We whittled up these little tube adapters to make up the size difference and positively locate the rear to the springs. We tack-welded them in place over the center bolt.
With the springs dropped at...
With the springs dropped at the back, the prepped rear was rolled into position. The nicely painted rearend looked too good to go into this grubby old B'Cuda's chassis.
The 8 3/4's axle tubes measure...
The 8 3/4's axle tubes measure 3 inches, while the 7 1/4's are a puny 2 1/2 inches. This necessitates changing the shock plates and U-bolts. We pulled a used set out of a box of miscellaneous rear-end brackets.
The 8 3/4 rear is 2.26 inches...
The 8 3/4 rear is 2.26 inches longer from the U-joint flange to the axle centerline, requiring a shorter driveshaft. Normally this would require a trip to the driveline shop, but luckily we had the old shaft from our 8 3/4-equipped Duster, which was just the correct length. It even had the 7260/7279 adapter U-joint we needed to adapt our small U-joint driveshaft to the new rear's large U-joint yoke.
Even with 10-inch slicks,...
Even with 10-inch slicks, we had plenty of room to go bigger on our Barracuda. The combination of our rear's wide B-Body brakes and the springs moved inboard will allow for a substantial increase in backspacing.