URBAN WARFARE
ARBY PREPARES HIS POR440 VALIANT FOR DRAG CHALLENGE BATTLE
WHAT a thrash it has been to get my POR440 VG Valiant back up and running after it being stuck in the USA for almost a year following Hot Rod Drag Week 2018. The car needed a big birthday; it had done Drag Challenge here in Australia, two years of racing and driving across the USA, and competed in two Drag Week events.
I had sold the old trusty Gen III iron-block 5.3-litre LS in the USA (it has since completed another Drag Week with the new owner) and we decided to replace it with a L33 stockbottom-end 5.3. The block was 109lb lighter than the old motor, and it has stock Gen IV conrods, the same Stage II cam, LS9 head gaskets, BTR .660in springs and ARP head bolts.
While the engine was out we changed to a PTC torque converter, gave everything a good clean-up and headed to Northmead Auto Centre to put a decent tune in the combination. The plan was to pump over 25psi of boost into the stock 328ci motor with the attitude that if it was going to grenade, best to do it on the dyno close to home rather than at a race track.
The problems started early; the most significant was a loss of fuel pressure once the engine saw boost. We ditched the four Bosch 044 pumps that had been in the car from day one and replaced them with new ones. But the fuel pressure problem persisted. Initially it seemed to be voltage drop at the pump, so we reassessed the size of the cabling, changed relays and individually earthed each pump. We essentially changed every component of the fuel system one piece at a time, and it took days to isolate a series of problems ranging from bad earths to a faulty alternator that showed great voltage but bad amperage. The real issue was naturally the last thing we changed: the 100-micron stainless gauze fuel filter, which had been on the car from the start. For some reason, even from low boost, it just could not handle the fuel flow of four pumps running at once. When we looked back through the datalog, the issue had been there the whole time and we’d essentially tuned around it, ignoring the data.
THE PROBLEMS STARTED EARLY; THE MOST SIGNIFICANT WAS A LOSS OF FUEL PRESSURE ONCE THE ENGINE SAW BOOST
Over the next few weeks it felt like we replaced everything in the car except the front windscreen. The biggest head-scratcher was that we kept running out of injector. The previous motor had shown 980fwhp based on weight and mph, and we had to keep bumping up the fuel pressure on the 1500cc
injectors that the ECU was telling us were now at full duty cycle.
The dyno figures were not great either – 710rwhp with 27psi of boost from a billetwheel S485 turbo and our base fuel pressure bumped up from 35 to 60lb, with a Weldon rising-rate regulator adding boost pressure to that as well. The boys at Quickbitz kept telling us to increase the base pressure, but the 044 pumps are only rated to 73lb, so if you start with 65lb and then add boost pressure on top, you are out of pump quickly.
We changed to a set of Precision injectors that are rated at 2400cc at 3bar and ported the hot side around the turbo flange, which made a huge difference, and ran the car to 7000rpm.
Despite the low power figures, the car felt strong on the dyno when the trans was cold. We needed a couple of heavyweights on the boot to keep it on the rollers, and after 100 pulls we couldn’t ignore the Haltech data: the amount of fuel consumption, boost and timing all added up to 1250fwhp.
We decided to give the transmission an oil change before heading to the Kenda Radial Riot at Willowbank, as the fluid didn’t look great and smelt burnt. The gearbox seemed fine, but we made a last-minute decision to swap out the PTC converter for an Aussie-built item. It had been too tight on the previous motor, but we felt with the extra 300hp on this new mill we might be okay.
We went to Kenda with a goal of running a 5.80 or better over the eighth-mile, in order to get us into the eight-second zone for the upcoming Drag Challenge (a 5.80 with give you roughly an 8.9 over the quarter). But from the outset we had issues.
We couldn’t get the car up onto boost. Even doing a burnout was a problem. After holding the car on the transbrake in the burnout for 10-13 seconds to get it up onto boost and then the same amount of time staging the car, intake temps went through the roof when we finally got going. The data showed we were at 51 degrees when we left the startline, and before the 660foot mark the high temps were triggering the engine protection, dropping cylinders. So we started bumping up our engine protection.
But with a too-tight converter we simply couldn’t get the car off the startline and our 60-foot times were appalling at 2.4 seconds. We made half a dozen passes but it was quickly obvious that until we fixed the converter issue we were not going to improve. We decided to pack it up as we were not achieving anything but torturing the transmission, and running with intake temps around 80 degrees was not going to do the motor any favours.
On the upside, the new Haltech bump-andcreep function was working mint, the engine saw 26.6psi of boost on almost every pass, and apart from high intake temps it seemed happy.
After being plagued by serpentine belt issues on every pass at Drag Week, we seemed to have that ironed out, even turning the motor to 7000rpm, and when we use the 60-foot time of 1.44 that the car usually runs, we are around our goal of 5.8 over the eighth.
Since returning home we have ditched the $300 ebay intercooler for a better-quality unit, swapped the PTC converter back in and are ready to hit the track again.
With the new aluminium block, the car’s weight has dropped to 3660lb. It seems our goal of
OUR GOAL OF RUNNING EIGHTS ON A 235 TYRE AND A STOCK 5.3 IS JUST A PASS OR TWO AWAY NOW, AND WE ARE PRETTY HAPPY
running eights on a 235 tyre and a stock 5.3 is just a pass or two away now, and we are pretty happy. Despite the lacklustre dyno figures, the car feels very strong, and even foot-braking with the new converter, the motor flashes to 3800rpm, so it seems getting up onto boost shouldn’t be an issue.
Massive thanks to Sumofab and Ben Doble for ongoing fabrication work, and especially Tyson, Nicholas and Bill from Northmead Auto Centre who have nailed a killer tune in the old girl and helped with 101 teething issues. With Drag Challenge just around the corner, the car has never felt better and we are excited about what it will do.
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