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
The first thing we had to do was to approximate how much room was
reasonably available. If you constrain yourself to not cutting
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 big mess before.
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
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.
Another before shot: ladder
bar on pass side.
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
showing some serious age and was probably restricting free axle movement.
Floater kit, before
disassembly, and old shock mount.
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
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
Pass side axle tube:
leaf spring, spring brackets and cheezy shock mount removed.
Now the fun begins... we took the plasma cutter and from inside of car,
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)
before any cutting, note frame rail angle, factory
upper shock mount
and cheezy existing upper shock mount bar.
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.
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.
the wheelwell is cut and frame section is notched.
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
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.
Lower shock mounts
and brackets. Old blue Monroe shocks
for mockup to prevent damage to new konis.
We then welded the relocated inner wheelwell shells into
their new 3" inboard locations. Amazingly, very little trimming
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.
Back half of pass
wheel tub and frame, all welded up.
With the bulk of the suspension work done, we then measured,
fabricated and tack welded the new upper shock mount cover panel into
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.
of welded tubs, cover plate and strut support.
fuel cell here for sanity checking purposes.
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
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.
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
||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)|
||Tom Alston HD bolt-on track locator kit|
||HAL Engineering 170# springs $35/ea|
||Tom Alston lower shock mount kit|
||Welding wire and gas|
||Mild steel for wheelwell fillers and upper shock
mount cover (with 90 degree brake by machine shop)|
||Replace 4 rear ladder bar bolts with grade 8|
||Tom Alston upper shock mount tabs|
||Mild steel for frame rail reconstruction|
||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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