WHENEVER somebody brings up the question of who has the quickest street car, itís like the bell going for round one. Everyone has their own definition of what Ďstreetí means. To me, driving 1300km and racing at five tracks in the Street Machine Drag Challenge goes a long way to highlighting which are Australiaís fastest true street machines. By the time you read this, Drag Challenge 2015 will be over; I canít wait to see the results.
Far North Queensland racer Mark Clifford has entered his midnine- second, naturally aspirated Boss-motored Mustang in Drag Challenge this year. While the car gets regularly driven to and from Palmyra Dragway, Mark spent a bit of time making sure the car was ready for the rigours of Drag Challenge. Future competitors might be interested in some of the prep work he carried out.
Anyone who has driven a car with low diff gears on the street knows what a pain they are. A manual with 4.11s and 26-inch-diameter tyres will be buzzing at 3300rpm at 100km/h (an auto would be close to 3500rpm, depending on converter slip). Certainly, a low-geared car can be street-driven, but itís definitely not a pleasant way to travel any distance on the road. Markís solution was to fit a Gear Vendors overdrive and a new tailshaft.
Markís next concern was the transmission heat created by the high-stall converter. At a steady 100km/h, the 5000rpm converter had 12 per cent slip and was the principal source of the transmission heat. So Mark added two large transmission oil coolers with electric fans. Next he fitted another C6 converter that only had six per cent slip at 100km/h. The Mustangís 3.7 diff gears, 28-inch street radials and the new 5000 stall coupled with the Gear Vendors brought the 100km/h cruising revs down from 3100rpm to 2400rpm. This has made the Mustang so much better for road driving, and Mark canít speak highly enough about the overdrive unit.
The other problem Mark had was that the C6 gearbox was sometimes locking up between gears. Phil Cruikshanks diagnosed the problem correctly as an old shift cable. As a cable gets old, it gets end-float and no longer has full travel for shifting. With a new shift cable the C6 worked fine again.
Mark wanted to tow a small trailer with his slicks and tools in it, like many other Drag Challenge competitors, but when he tried towing a trailer the motor started to get hot. The practical solution cost just $30; he fitted a set of roof racks to the Mustang to strap the slicks on, while the frontrunners go behind the rollcage in the back, along with the tools. It mightnít look cool, but it means Mark is a contender for the Quickest Without A Trailer trophy.
Before embarking on the interstate journey, Mark wisely put the Mustang on Deric Clapsonís chassis dyno, while Dave Sheehy did the dyno tuning. It wasnít so much to try and find more power, more a chance to give the íStang a general health check. The first power run there saw a puff of smoke when transmission oil hit the extractor.
Looking under the car, there was a couple of drops of trans oil on the floor from a melted plastic breather hose. The problem was easily fixed, but could have been a drama if it had happened on the road or at the track.
Mark also wanted to see how a smaller carb compared to the original Dominator fitted to the Jon Kaase motor. It turned out that the small carb lost 30hp on the dyno, but made the car so much better to drive on the road.
In reality, it only takes a few minutes to swap carbs at the track.
However at the Portland eighth-mile track the small carb ran a 6.08@115 mph, which works out to 9.618 seconds over the quarter, so the time lost by using the small carb instead of the Dominator was less than a tenth over the eighth-mile.
It was so good to see the Mustang run the same times at Calder as it does at Palmyra. The Jon Kaase-built Boss motor makes 1000hp on an engine dyno, and ran 9.58@143mph on pump gas at Calder, which is just under 900hp by weight shifted over the quarter. Mark says that the donk is five years old and is probably due for its first set of rings. Thatís a tough crate motor!
To me, what sets Markís 3850lb Mustang apart from many of the competitors is that itís like a naturally aspirated muscle car that was available off the showroom floor in a bygone era. It mightnít have the original seats, and now has a rollcage, but a Boss 429 was an optional motor in the Mustang. Those seats are mandated by ANDRA; if Mark had his way they would be comfortable Recaros or something similar. But the Mustang is as close to original as can be within ANDRA rules.
I donít care if youíre a Holden, Chevy or Mopar lover; itís very hard not to be impressed by this Ford. s