Minitub Project of '67 Camaro


This describes the steps we took to make room to move the rear tires inboard 3" on each side of the project '67 Camaro while converting it from a hardly-functional leaf/floater to a full coil-over setup.

Preparation Phase

The first thing we had to do was to approximate how much room was reasonably available. If you constrain yourself to not cutting

before, big mess

The big mess before.
into the factory frame, you could probably only get an extra inch and a half... hardly worth the effort. With some crude measurements, it appeared that cutting over to the heavy vertical floor reinforcement inside the upper factory shock mounts would yield an additional 3", but would require some notching of the rear part of the factory frame rails.

The next step was to remove the back half of the interior and everything from trunk including N2O brackets, battery and fuel cell and lines.

Next, we computed approximately where the new upper shock mount location would be based on coil-over shock normal compressed height and adjustibility
before, ladder bar
Another before shot: ladder bar on pass side.
of lower mounts. The coil-over shocks have a stroke of around 5" ( 10 3/4" compressed and 15 7/8" extended), and the general rule of thumb is for them to be at 60% of compression when the vehicle is still. Even though the Alston lower mount kit allows 4" of ride height adjustment, we figured that the existing upper shock mount bar (installed by a previous owner) would not allow the Camaro to sit down low enough in the back (not to mention the fact that the bar was installed crooked by 1/2" front to back!). This ultimately added tons of work in addition to cutting the trunk to mount the bar high between the frame rails, but worked out for the best in the end.

Destruction Phase

The first item of disassembly was to unbolt the old single leaf springs and perch mount brackets. Not amazingly, all the original bolts came loose without a hitch. The floater kit (which is supposed to allow free rotation of the axle without binding of the leaf spring) was also
floater kit
Floater kit, before disassembly, and old shock mount.
showing some serious age and was probably restricting free axle movement.

This photo also shows the existing shock mount system and displays one of the biggest problems with the existing suspension (and why the car never really hooked up that well)... in particular, look at the mounting technique for the lower shock bolt and how it would actually resist the rotation of the axle. The leaf spring/floater kit setup is challenged enough as it is to generate a hard seperation (thereby planting the tires) without added restriction from things like shock interference.

The first really destructive job was to cut off and ground clean the old leaf spring perches from the axle tubes. We originally weren't
axle tube sans brackets
Pass side axle tube: leaf spring, spring brackets and cheezy shock mount removed.
going to narrow the axle housing, so we spent the extra time cleaning up the axle tubes. At first thought, this may not have been necessary since we ended up cutting 3" off the end of the axles tubes... but had the brackets still been there, we probably would not have gotten a clean cut, so there was no real labor lost there. We also cleaned up the cheezy old lower shock mount brackets that someone had added to the rear of the ladder bar brackets.

Now the fun begins... we took the plasma cutter and from inside of car,
before the big cut
Virginal floor: before any cutting, note frame rail angle, factory
upper shock mount and cheezy existing upper shock mount bar.
cut out inner dome of the upper wheelhousing. Even with the full 10pt cage, you can sense that the layers of factory metal (albeit not really heavy gauge stuff) are definitely structural in nature and absolutely needed to maintain chassis rigidity in anything short of a full tube frame. We easily decided that when it came time to reassemble and reweld everything, that we simply must make full welds (as opposed to tack welds with holes filled with body dumdum)

With the inner wheelwells gone, we marked inboard on floor 3" of the old location and cut down from inside of car with the plasma cutter.
holy wheelwells
Holy wheelwells! the wheelwell is cut and frame section is notched.
From the bottom, we cut the "chunk" or notch out of rear frame rails that interfered with the new wheelwell location. Due to having to run the new upper shock mount location higher, we cut a section out of the trunk floor to allow placement and access to the new upper shock mount bar. Finally, we cut out the old small square upper shock mount bar and cleaned up the frame rails where it had been mounted.

Construction Phase

We started construction by focusing on the suspension first. We measured, computed, thought, remeasured and measured again for the new upper shock mount bar. The objective here is to keep the shocks near vertical, but provide a slight angle (so that the lower part of the shock is slightly forward of the top part of the shocks) if necessary to prevent any sort of binding or contact between
lower shock mounts
Lower shock mounts and brackets. Old blue Monroe shocks
were used for mockup to prevent damage to new konis.
the shock bodies and the axle or frame components. Once the bar was in place, we figured the proper location and tack welded the upper shock mount tabs on the cross bar and the lower shock mount brackets on the axle housing. Much care is needed here to ensure that the housing is centered under the car to prevent any strange angles (left to right) between the top and bottom of the shocks. Once we were confident everything was lined up properly, Jon put a final weld on them.

We then welded the relocated inner wheelwell shells into their new 3" inboard locations. Amazingly, very little trimming
welded tubs and frame
Back half of pass wheel tub and frame, all welded up.
was needed to the overall shape of the relocated metal... all that was needed was a little bit of cleaning of the 31 years of road grime and tire rubber off the welding surfaces in the bead blaster. Once the wheel halves were in place, we worked around the wheelwells (one person inside the car and one under the car), and fabricated and welded the 3" wide filler metal sheets to fill in the gaps. We then fabricated and welded new heavier gauge metal into the notched sections of rear frame rails.

With the bulk of the suspension work done, we then measured, fabricated and tack welded the new upper shock mount cover panel into
trunk view
Trunk view of welded tubs, cover plate and strut support.
Bottle and fuel cell here for sanity checking purposes.
the trunk floor. Since the weight of the car would now be supported by the coil springs on the shocks (instead of the leaf springs which we had removed), the upper shock mounts needed to be reinforced. Ideally, we would have anticipated the installation of coil-overs when we installed the 10-pt cage and would have run the "X" bars down to the upper shock mounts. Instead, the "X" bars were run to the reinforced floor area near the factory upper shock mount locations. As an alternative, we fabricated and welded tubular strut bars from the "back" bars of the roll cage to small metal pads that we welded to the top of the upper shock mounts.

Final Assembly Phase

We measured and cut the new Alston track locator bar to length and welded the threaded tube ends into the bar. Since I also wanted to move the front ladder bar location to the higher notch, we did that (as well as adjust the rear end location front-to- rear) before cutting and welding the locator. There are several different camps on whether to use a panhard bar or a track locator. The panhard bar, which runs parallel to the axles is generally stronger and more suitable for street use, BUT is typically more difficult to mount without causing interference in a low drag racing-oriented car. Tom Alston swears by the track locator, which runs diagonally from the lower rear mount point of one ladder bar to the front mount point of the other ladder bar, due to the fact that they rarely cause interference and especially because they generally provide a more consistent track as the rear end moves through its travel.

We also had to modify the lower shock mount adjustible brackets to accept the Koni shocks with the orientation we needed to run them -> will order new correct brackets from Chassis Engineering. Finally, we assembled the coil-over shocks with the 170 lb/in springs and test mounted to the car and adjusted the lower brackets for proper ride height.

Problem arises! When we were adjusting the front rod end to move the axle forward a bit, we quickly found that the rod had become "frozen" in the ladder bar tube and was eating the threads. We rigged up a temporary fix to get the car home, but this will require a new $65 ladder bar on the driver side.

Cleanup Phase

Still left to do is grind all welds in wheelwells for cleaner appearance, and prime/paint all metal surfaces. You wouldn't believe how fast bare steel will rust when you trailer your car in an open trailer on a snowy day!
I will put some "finished" pics here once it's all finally completed!

Parts List and Costs

$618 Koni double adj coil-over drag shocks $309/ea (could have saved several hundred $$$ here on cheaper shocks, but wanted "the best" for an 8-second capable chassis)
$110 Tom Alston HD bolt-on track locator kit
$70 HAL Engineering 170# springs $35/ea
$55 Tom Alston lower shock mount kit
$30 Welding wire and gas
$10 Mild steel for wheelwell fillers and upper shock mount cover (with 90 degree brake by machine shop)
$7 Replace 4 rear ladder bar bolts with grade 8
$6 Tom Alston upper shock mount tabs
$5 Mild steel for frame rail reconstruction
$911 Total mini-tub and coil-over parts cost

Next in the series... we narrow the 12 bolt housing 3 inches on each side!

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