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GTO re-build

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  • GTO re-build

    Hi all,

    It's been quite a while but I've finally thrown together a build thread on the old GTO.

    Here's a little back story for those interested:

    1972 saw Mitsubishi Japan keen to tackle the Safari type rallies - this time with their new GTO.
    They only built two cars - one for Andrew Cowan to campaign and the second for a Japanese or local Australian driver.
    They attracted a lot of attention both in Japan and Australia. However, there was a problem..............

    Only a very basic roll cage with main hoop and single back leg was used back then.
    Consequently with the pillarless coupe design, body flex became a major issue at high speed on rough roads.
    During testing prior to 'The Cross', Andrew found the handling too unpredictable at high speeds. Losing confidence in the (otherwise quick) GTO, he switched back to the slower but more well-known GA 4dr (in which he won the Event).

    Pic below shows Andrew Cowan/John Bryson competing in the KLG Rally in Doug Stewart's car. Sadly this car too was later rolled and destroyed by another driver.............
    Both wrecked GTO's went back to Japan, never to be seen again.......
    It had a VERY short moment in the sun and history shows that the LA Lancer appeared the very next year - thus relegating the GTO to a footnote in rallying history....

    We believe it may well be the only competition rallying log-booked GTO in existence and while it needed a full re-build it seemed fitting to do ours as a Works Car.

    All rust repaired, about a thousand holes welded up, floorpan straightened and repaired from years of stone damage.
    More hours spent on repairing this shell than I would care to add up......

    We 'captive-nutted' with nylocks wherever possible.

    Almost ready to put back together - note the tags below the rear panel - they're for the straps holding the fuel tank guard.

    Works cars used the original GA style tank with holes drilled through the wheel-well section and a round, flat plate welded over the top which turned them into a 90 litre long range tank for endurance events. They also moved the filler neck inboard to help reduce damage by rocks/stones.
    We also fitted two pick-up lines, one for each fuel pump..

    The 8 bolt diffs are getting much harder to find and require regular servicing and given the car will actually be used in competition, so we decided to fit a 10 bolt Scorpion diff housing with Starion vented rotors/calipers and a 4.6 LSD, new spring perches and rotated the caliper mounts from leading to trailing so they wouldn't foul the shockers.
    New hard lines were done with clear plastic sleeving to protect from stone damage and new braided lines made/fitted to the calipers etc.
    Leaf springs are wagon with new nylon slipper pads, one 1/2 leaf removed and an extra 1/2 leaf inverted, then added to the top front half of the pack - this virtually eliminates axle tramp and still allows good 'squat'. Nolathane bushes throughout.

    Tank guard fitted

    Starting to take shape.
    Front struts are another departure from original due to the small original brakes and strut size. We often bent stub axles on the smaller Galant units so decided to go to the bigger Sigma units with adjustable coilovers/40mm Bilstein inserts and adjustable tops. They brakes are stock Sigma II with race pads but will be changed to Starion or similar vented units at a later date.

    Front end has remained essentially stock but fitted with later GC arms and the larger ball joints - Nolathane bushes. Engine crossmember gusseted.
    Twin spares mounted for the endurance events - same frame design as Works cars, however they only ran very lightweight 'bungee' straps to hold down the wheels
    We decided on something a little sturdier - wheel braces that secure onto threaded rods.
    The wheels are a tight fit but most importantly, clear the fuel pumps and still allow us to use the original jack/winder mounts on the driver's side of the boot.

    Back on wheels - all steel panels but long term we will run fibreglass front panels and put the steel panels aside due to their increasing rarity.

    The Works cars ran a (homologated) 4G35 which as some may know, is essentially a 4G32 Saturn block with thicker bore castings allowing capacity to be stretched up to 1800cc. This, combined with the hardened steel crank, oversize valves, twin 44 sidedraft Solexes and the #5 cam made them pretty potent. Most will know this as the 'C3 kit'.
    Block crack tested, line bored, casting de-dagged and polished

    Bored, zero deck height.
    Forged 81mm pistons, full floating.

    Retained factory rods, shot-peened etc, ARP's fitted and converted to full floating small end.
    ARP stud kit
    Rotatiing assembly balanced incl clutch, flywheel etc.
    Exedy HD button clutch
    1kg removed from the flywheel.
    OS stainless valves with 7mm stems.
    Nissan FJ20 double valve springs, titanium retainers

    Porting done and flow benched
    Works #5 cam

    Distributor was converted to Electronic and an MSD 6AL-2 controller used
    Headers are Hurricane 4 into 1
    Sump is baffled

    Original CR Works KM132 gearboxes are simply impossible to find so (some may remember) we sourced close ratio gearsets from Holinger here in Aus. I've been informed they will NOT be making them it looks like I have the last set..
    This gearset completely transforms the car and was worth every single cent!!!

    2, 1/4" exhaust with single turbo type muffler and rear resonator.

    Radiator has original tanks but with triple core done.
    Alternator is a GM 85amp unit with inbuilt reg and larger billet pulley.
    Water pump pulley is larger C3 type

    The 50th Anniversary Southern Cross was an amazing event - 3,500km over 12 days with 40 Special Stages ranging from fast route charted forest stages to navigational night stages, bitumen sprints, hillclimbs, auto/rallycross and Khanacrosses. ANY small mistakes cost dearly due to the timing/scoring system.

    Well, we finished the event with only a few minor hiccups and our little GTO came home in 2nd Outright.
    After all the original handling woes of the original GTO's, all it took was a decent roll cage, tagged to all the pillars to transform it into a sheer delight to drive on dirt and ultimately very competitive.
    Imagine if they'd worked this out back then...........

  • #2
    Wow. Well done that looks excellent.
    P510 Bluebird SSS Coupe


    • #3
      Wow, what a great story, restoration and final result. 3.500 km rally and becoming second, a well deserved result!
      '90 N13 Sunny 1.6 GT - '00 P11-144 Primera 1.8 - '88 N13 Sunny 1.6 GTi - '00 Micra Aztec 1.3i