Chris Isaacs race cars

Unique vision - innovative design - quality fabrication

CIRC has been commissioned to turn this innocent little Fiat into a potential 9-second street car using Gary's 500hp turbo rotary motor and a 5-speed transaxle combined with our own chrome-moly rear-half chassis, roll cage, and double-wishbone independent rear suspension.  Gary likes the look of the historic circuit racing Fiat 600's, and has purchased the Abarth arch kit which those cars run, along with a period-looking set of 9" x 13" Superlite wheels.
First job once the Fiat was put on the jig was to temporarily attach the arches and find the rear axle centreline.  The Abarth arches are around 2" wider and 2" further up the body than stock.

Even though the Abarth arches give some extra tyre room, the size of wheel that Gary is using has necessitated a mini-tub job on the Fiat.  The existing inner wheelwells were carefully removed, banded with fresh sheet steel, the seam smoothed off, and the now-wider tubs refitted to give 2" more width and 1.5" more height than stock.  As seen here, this still gives a standard-type appearance whilst giving the required tyre clearances.
Also shown here on the right are the first two chrome-moly rear chassis tubes tacked in place. 

The suspension design has already been finalized on CIRC's own CAD program, and shown here are the components of the rear suspension being constructed on their bespoke jigs: the upper wishbone on the left, the fabricated hub carrier in centre.  On the right, the suspension components jigged up and mounted onto the new rear half-chassis.


The rear-half chassis under construction.  The A-arms are already mounted here, and the coilovers are currently represented by the threaded bars which run from the upper A-arms to the turrets on the chassis.  On the right is shown the engine/trans adaptor plate, which has been waterjet cut from 25mm thick aluminium and which bolts direct to the upper and lower chassis rails and thus becomes a stressed chassis member.

The chrome-moly cage prior to welding.  This ties into the rear chassis to form a stiff but lightweight structure.  Still to come is the dash bar beneath the steering column, plus some tubework running forward to pick up the new front suspension - but these bars will wait until the new, CIRC-designed front suspension and steering are fabricated.

The first stage of work completed.  The Fiat still looks quite innocent on the outside...

...But it's all going on underneath!  The little Fiat will be back at the start of 2013 for front suspension, tinwork and a host of other jobs.


... Early 2013 and it's time for part 2 of the Fiat build....

The rear tinwork has been finished apart from a panel at the very front of the gearbox cover - this will be finished once the gearshift mechanisms have been finalised.


Gary didn't want a big, square box covering his new chassis, so we have made sheetmetal 'turrets' to cover the rear coilovers, whilst the floor between the turrets has been kept as low as possible over the gearbox and bellhousing.  The panels have been bead-rolled in a style similar to the original floorpans for as close to a factory look as possible.

The turbo is mounted onto a bolt-on rear subframe that will also provide front engine mounting points and wheelie bar mounts. Slip joints in the stainless exhaust manifold will allow for expansion of the system between the solid mounted engine and turbo.

The lefthand and centre photos show how the subframe picks up the front of the motor and will also pick up the lower wheelie bar tubes.  The right-hand photo shows the upper tube of the subframe just above the rear valance, which will mount the upper wheelie bar tubes.

Unsurprisingly, Gary decided that the original Fiat drum brakes, wandery steering and transverse leaf spring suspension were somewhat deficient for fast street, strip and track day use, so instead is using a HiSpec Motorsport upright and 4-pot vented disc kit with CIRC designed and constructed double wishbone suspension, with the coilovers cantilevered off of the lower A-arm.  The dampers in these photos are old setup units, not the finished articles.

The front suspension and steering is complete apart from the anti-roll bar.  The steering rack is an Escort quick ratio item which is linked into the original Fiat upper steering column, and will be eventually topped with a 1970's-era Abarth sport wheel.

The custom anti-roll bars are now installed - the front bar is shown in the two LH photos, the rear bar at the right.  The spring and bar rates have been calculated to give balanced cornering with a reasonable degree of roll on sticky street tyres.

The front track has been widened 2" each side to match the rear, and this will require additional front wheelarch clearance to get full suspension movement and adjustment.  The original Abarth cars used to radius the front wing and weld a simple, horizontal extension out to the tyre edge.  We are going with something a bit more stylish, moving the standard wheelarch lip out and creating something like a MK 1 Escort Mexico style front wing lip.  A racer-tape and rattle-can mockup is shown in the RH photo.


The exhaust system is fabricated from 321 stainless steel, and includes slip-joints in  both the prmimary tubes and in the wastegate exit tube, to allow for heat expansion.  The wastegate is protected from 'stuff' thrown up by the rear tyre by the quick-release splash panel shown in the RH photo.  This panel can be easily removed for wastegate maintenance and adjustment.  The muffler will eventually run across the back of the car, between the upper and lower wheelie bar tubes.

The second stage of the build is complete.  Just visible behind the Abarth nosecone is the new aluminium water radiator.  The Fiat will be back for mounting of intercooler, seats, pedals and a variety of other jobs soon.