Installing A Pacer IFS in a GM truck

I have had a few inquiries about the Pacer IFS I installed in my ’51 GMC. I will attempt to describe this conversion for those who may be interested. Also some of the other IFS options are mentioned, for comparison purposes. I researched all the ways to do an IFS on my truck, and have friends who have done both subframe and Mustang conversions on their trucks. I have driven examples of each. While I am no expert, I have been down this road before, and hopefully can supply some information to those who are considering the same alternatives.

Why a Pacer?

The AMC Pacer was built between 1975 and 1980. The Pacer came with either 4, 6 or V8 engines. It has become somewhat of a laughing-stock car these days, an icon of the ’70s, a typical “Nerd Car” as featured in Wayne’s World. True, the Pacer was somewhat ahead of its time styling wise (but compare it to the latest Subaru Outback). About the time Pacers started appearing junkyards, somebody did some measuring and discovered that A) the track of the Pacer was almost identical to a ’47 – 54 GM truck, and B) the bolt-in front IFS crossmember could easily be adapted to the truck frame.

Converting an AD (Advance Design) GM truck to a modern IFS has numerous advantages for those owners not concerned with maintaining originality. The factory beam axle, leaf spring front suspension is a rugged but antiquated design, and when well worn, can be very uncomfortable, unsafe, and near uncivilised to drive. In addition, parts to rebuild the original suspension, brakes and steering, while readily available, are far from cheap. Many owners elect to replace the entire front end with a suspension of modern design, and gain the advantages of disk brakes, smoother ride, and better steering all in one conversion. There are several ways to accomplish this.

Subframe (clip) conversions

This method requires cutting the truck frame off ahead of the firewall, and welding on a new frame section (subframe) from a donor car. This radical surgery is pretty much irreversible. Once the frame is cut, there is no going back. Common candidates are the early Camaro and Firebird. Later Camaro clips can be used, but must be narrowed. All of the modern suspension pieces come attached to this new subframe. The radiator core support must be adapted to the new subframe, because this orients the attachment points for the fenders, grille, and other front sheet metal. Depending on mileage and condition of the donor car, some or all of the suspension, brakes and steering gear will require rebuilding. The Camaro uses a steering box. There are many successful examples on the road; this can be an excellent conversion IF it is done right. Not for the novice!

Mustang II front suspension

This option is widely advertised in the “Classic Truck” Magazines. There is a very competitive industry which supplies Mustang IFS kits to the Street Rodder hobby, not just for old trucks but for many other applications. Based on the Pinto / Mustang II IFS, these kits can be upgraded with many show and performance options. Installation requires boxing the frame and welding in a crossmember to which the IFS and steering gear is attached. Some of the major suppliers are Fatman’s, Heidts, Kugel and other well-known, credible fabricators. Some fabrication and chassis expertise is required (the more the better).

Other possibilities:

There is a 3rd option available that I don’t have first-hand experience with: the Mopar torsion bar front IFS conversion. Gibbon Fiberglass out of Nebraska sells it as a kit (around $400). It involves a crossmember, like the Mustang, but uses torsion bars instead of coil springs. This kit requires use of a donor car for the suspension and brake parts, which is a Plymouth Satellite, Dodge Cordoba or the like. These were ’70s vintage midsize Chrysler products and are still to be found cheap in wrecking yards. The big thing the Mopar kit has going for it, is that the torsion bars are adjustable for ride height, so you can drop the front end for a show and then raise it up for normal driving.

The Plymouth Volare/Dodge Aspen IFS seem to be popular conversions for early Ford truck conversions, but I don’t know what is involved with these and did not research them.

Of course, given enough time and money, the possibilities are endless. Some owners have literally transplanted their old trucks onto later chassis, including 4 x 4, Corvettes etc. This level of modification was beyond my skills and capability so was not considered.

Decision Time

Cost was a big factor for me. I was quoted about $2500 – $3000 for a turnkey Mustang II or subframe job. Of course Camaro clips are cheap but I factored in the cost of all new suspension and brake parts, so the cost came out about equal. Labour was the big cost here. At the time, I had no access to welding equipment and had no chassis fabrication experience, so I wanted an option that would keep outside labour to a minimum. The Pacer solution would allow that. One big problem with the clip conversion was I could not find a builder who inspired any confidence in their ability to do the job successfully or stay within my budget. I felt I could probably handle a Mustang conversion, but would need some help with the welding. Again the cost was a factor, I could just order up all brand-new components shiny clean in boxes delivered to my doorstep, but a big chunk of money was required. With the Pacer, I could get the subframe ready for attachment, rebuild all the components as time and budget allowed (in my garage with the usual hand tools), have the minimal welding done and still continue to drive my truck. When everything was ready, it would be a straightforward “Off with the old, on with the new” procedure (Well, almost).

Oh, one other plus for the Pacer: it can be installed without removing the engine, or even the front sheet metal (fenders, hood, grill etc). When your facilities are limited to a small garage, like mine, this is a big help. But, if you are looking for a super-slammed low front end, the Pacer is probably not going to work out well. It will lower the front end a couple of inches, but nothing like what you can get with a subframe or Mustang II with dropped spindles. Cutting spring coils would get it lower, but would result in a harsher ride.

What’s involved

The Pacer conversion differs from the others mentioned in that it is a BOLT-IN operation. This is the way AMC Pacers came from the factory – the Suspension unit (which is not really a subframe, it is really a crossmember with suspension components attached) just bolted up to the frame. The “crossmember” is a hefty steel stamping; very strong and heavy compared to the Mustang. Engine mounts in the AMC application were attached to this crossmember. They are not used on an AD truck conversion. These motor mounts, and other unneeded frame extensions, are cut off with a torch or die grinder prior to starting any further work on the conversion. Once the crossmember is “cleaned” of all this superfluous metal, it is much more compact and lighter looking, although still quite substantial. Once the crossmember is ready, the mounting brackets will need to be welded on. These brackets can be purchased as a kit from:

Chassis Engineering
P.O. Box 70
West Branch, IA 52358
Phone: (319) 643-2645
Fax: (319) 643-2801

A one-page instruction sheet accompanies the kit. It is very sparse and only covers how to clean the crossmember and mount the brackets. PS there is another Chassis Engineering in Jupiter FL. No relation!

Once the unneeded metal is removed from the crossmember, there will be a flat surface to weld the brackets that attach to the frame. Basically you need (and the CEI kit supplies) a reinforced L-shaped steel plate which will attach to the outside of the truck frame rails, and the lower part of the rail rests on the reinforced crossmember. A little study and you could probably build your own brackets, but the CEI kit is cheap at $100.

You can bolt it on the frame using grade 8, 3/8″ bolts and locknuts, as I did, or it can be welded in place.

What to look for

Most Pacers came with 232 or 258 inline 6 engines, power steering and power brakes. These were fairly heavy cars, at 3400 – 3500 lbs. So the total weight, and weight distribution supported by the front end, is a good match for the AD truck chassis. Some fleet cars came with 4-cylinder engines and manual steering. I would avoid these, as the springs are too light for a truck. I didn’t particularly want or need power steering, but the only donor cars I could locate had power racks. When I started calling around, to NAPA and other parts sources, I discovered that manual Pacer racks were no longer available except on special order (i.e., the rebuilder would use your core) and were VERY costly like $295 vs. $135 for a rebuilt power rack. So plan on using a power steering pump, unless you know how to convert a power rack to manual. Once I got used to power steering, I would never go back! Other usable parts from the donor car are the brake booster and master cylinder with proportioning valve, steering column, and power steering pump. Removal of the suspension from the Pacer is straightforward, but does require removal of the upper control arms to clear the frame. If a junkyard does this for you, be careful not to lose the studs and bolts, as they are an uncommon size and hard to find. Try to keep wheels mounted so you can roll this hideous, greasy lump around and hide it from your wife.

Parts needed

Total bill of materials will depend on the condition of the donor car. Most Pacers are pretty trashed so plan on most if not all of the following.

Upper and lower control arm bushings
Upper and lower Ball joints
Tie rod ends
Shock absorbers
Steering rack
Sway bar bushings
Calipers
Rotors
Brake hoses
Wheel bearings and seals

I found the best prices and availability from Auto Zone, but any parts store can supply these pieces. Kanter had the best deal on a front-end kit which includes many of the above for a good saving over individual pieces.

If you can get an AMC shop manual, which shows overhaul procedures and exploded views of these components, especially the way the steering knuckles go together, it will make your life a lot easier. Since all of this is typical IFS assembly, I won’t go into detail. A Motor’s or Chilton manual can give you everything you need to know here. Be safe; use spring compressors to install the coil springs! Likewise, removing the old stock axle, steering gear etc are straightforward and covered in the truck shop manual.

Hooking up the steering rack: I used two Flaming River steering joints, which were among the most costly parts of this conversion, at $70 each. I used the stock ’51 steering column, which I sawed off at the steering box (both column and inner shaft can be cut by hacksaw). You will need a bearing to position the shaft in the column. A Toro lawn mower shop can supply a steering bearing for about $7. Sorry I’ve lost the part number but it’s ¾” ID – bring a section of steering column with you and they can find the right one. It just taps into the column, and doesn’t really carry any load, but just positions the shaft. Cut the column so as to have about 6 inches on the engine side of the firewall.
(Note: I am running an Inline Six so had no problem with steering shaft interference – if a V8 is used, install it first. You may have to shorten the column and use an extra U-joint for room around headers). I did not use anything other than the stock U-clamp to secure the column – a firewall mount would be a good idea. Also a note on steering joints: There are a huge variety of shafts and spline sizes. Get your rebuilt rack and order the lower joint to fit the new rack. Don’t trust the parts store to return you a rack with the same spline as your core! I learned this the hard way.

The CEI kit includes a drawing showing a 20 – 1/8″ measurement from the front of the Pacer crossmember to the end of the truck frame. Use this only as a rough guide – lower the truck down into close to final position, with at least one, preferably both, wheels and tires mounted. Do this to make absolutely sure the wheels are centred in the wheel well openings. Especially important if you are going to weld the brackets to the frame.

Speaking of wheels, the Pacer rotors use a 5 lug, 4-1/2″ bolt circle pattern. This is commonly known as the “small Ford” pattern. Many Mopar rims also use this pattern so it is no problem finding rims to fit – just be sure there is adequate backspacing to clear the tie rod ends and brake calipers.

Brakes

Some assembly required here. You must change to a dual chamber, disk/drum master cylinder, and make up some new brake lines to provide two separate circuits. Since I did not plan to use power brakes, I found a master cylinder from a ’73 Chevelle which came with non-power front disks and rear drums. Using an adapter bracket from Jim Carter antique trucks ($85 -ouch), it mounts close to the original spot under the floor. Of course you could a power booster and M/C on the firewall, change to a swinging brake pedal and do it that way, or get one of the compact MC/booster units that street rods use, and keep it under the floor. Whatever, you will probably need a proportioning valve in the rear brake circuit to keep the drums from premature lockup. Best price I found was from Summit racing, about $52. I was told I would need a residual pressure valve in the front circuit. This is an inline valve that costs about $10 and is supposed to keep pressure on the calipers to avoid fluid draining back into the MC. Well, it was back-ordered, so I drove the truck for a couple of weeks and noticed no ill effects, but did install one later. I would say the brakes are adequate for stopping a ½ ton truck – certainly much better than the stock drums – but I am looking into upgrading to 11″ rotors and calipers from a Matador or other large AMC car. Since the Pacer steering knuckles bolt together, spindles and caliper brackets can be replaced with those from another front end. I will update this document, if and when this modification works out. A power booster would be nice too.

Epilogue

I have about $1200 total in my Pacer conversion. All of the suspension parts, brakes and steering were either new or rebuilt, so it could be done for less if you can find a low-mileage donor car. I am, to say the least, very pleased with the result (I have been driving it for almost 3 years now). The steering, brakes and ride are so far improved over stock, that there is just no comparison. It’s still an old truck, but just rides, steers, and stops a lot better. The only problems so far have been a leaking steering rack, replaced by Auto Zone at no charge – their rebuilt racks have a lifetime warranty. Also, one “aw s#!t” – the discovery that the bottom of the oil pan was too close to the crossmember to drop the pan, when the pan gasket began leaking. No problem, just disconnect power steering, brake lines, remove 6 bolts on each side, and roll the whole front end out of the way.

This truck gets driven a lot. I have close to 30K miles on it since the conversion, and am lovin’ it more with every mile! I’m not promoting the Pacer IFS over the Mustang or clip methods, but it certainly worked out well for me. Remember that the steering hookup and brake mods will be required with any IFS setup. As far as Pacer parts supply goes, I had no problem finding any of the parts I needed. How long this will be the case, I don’t know.