I’ve been resisting the temptation to write anything about my POR440 VG Valiant hardtop for some time, despite it being in a constant state of evolution. My goalposts for the turbo LS-powered car have shifted over time from it being a 10-second slapper to running nines over the quarter-mile, and then eights. The current aim is to get it into the sevens, but I knew that wouldn’t happen without some further development.

In that regard, Street Machine Drag Challenge 2024 was a big milestone in my journey with car. Not only was it the first Australian drag-and-drive event I’d done in a few years, but the work I did on the Val in the lead-up saw some of its best performance advances.

Not long ago, we decided to retire POR440’s stock 5.3-litre LS, which had run a best of 9.0@152mph. We had been beating on that stock motor so hard for so long that it was only a matter of time before it all went south. We’d also hit a wall in terms of going quicker; no matter what we threw at it – more boost, more fuel, different converter, different kitchen sink – the car had just plateaued for no obvious reason.

We pulled the motor, and while ditching elements of the hot-side, we noticed the front crossover pipe with a flexible stainless joint had collapsed internally, all but totally blocking it. It looked mint on the outside, but it was junk, which explained why no matter what we did, the car would not go one mph faster or a tenth quicker. It had cost us about two years in development!

We decided to stick with the factory alloy-block 5.3 but fit a forged rotating assembly and step up the S485 turbo to a 92mm, S480-frame BorgWarner item.

Straight away, the car dipped into the eights, running an 8.80, then an 8.60, an 8.50 and eventually an 8.38 on 32psi of boost. Now we’re getting somewhere!

However, while the bigger turbo made power gains, it also made it harder to get off the line, as it wouldn’t make boost at lower revs on the two-step, which meant having to leave on 4300-4500rpm to get it to make 10psi on the launch. This was far from ideal, as it would knock the tyres off either on the hit or at the 60-foot mark as we put power in the car to get it moving.

The other issue – and of more concern – was that the relatively primitive (and older journal-bearing design) turbo created big intake temps at the top of the track when we had 30psi of boost in it, despite the car running a huge, good-quality bar-and-plate intercooler. We just could not get the car to 60-foot, and we would have had to fit a water/meth kit to keep a lid on intake temps.

The best fix was to finally install a good-quality turbo that would spool easier at lower revs to allow the tyre to plant and drive out of the hole. After doing a little homework, a Garrett GTX55 92mm unit was the perfect fit for this engine combo, with a 1.00 rear housing instead of the 1.32 we were running on the BorgWarner.

So, the plan to be ready for Drag Challenge well in advance went down the crapper and the thrash was now on, with only a week left before the start of the event to change turbos and try to test it. The guys at Northmead Auto Centre basically dropped everything to get the car in for the fab change and a dyno tune.

Luckily, the GTX55 had a T6 exhaust housing rather than a V-band like most modern set-ups, so the turbo basically bolted on with only a few minor mods. This was clearly meant to be! It was then up to Northmead Auto Centre’s Nick and Michael Tzavaras to remake the dump pipe, and we ditched all the silicone joints for V-band joints. 

Earlier in the car’s development, the front shocks would top out when we started adding power on the launch, which would then unload the rear tyre. The AFCO/Gazzard Brothers shocks were already on the maximum extension setting, so we sent them to the AFCO Shock Doctor in Queensland to have them re-valved to give us more control over the rate of extension.

While we were making suspension changes, Brody from Davies Customs fitted a Mood Motorsports anti-roll bar in the rear and modified the rear shock mounting plates for street and track usage in order to get full range from the Gazzard shocks. We knew we were on the right track and that it would all come together.

As luck had it, there was a track day at Sydney Dragway before Drag Challenge, so we took the rejuvenated POR440 along for some testing. The results were instant, with the most exciting improvement coming in the 60-foot. The car could now leave on much lower rpm but with more boost. My previous best 60-foot in this 3800lb sled was a 1.402, but we were now improving on that pass after pass – 1.38, then 1.32, 1.28, and finally a 1.25. While this may not seem impressive for something like a Fox-body Mustang or a well-sorted first-gen Commodore, for an old, heavyweight sled with a torsion-bar front like my Val, it was an awesome result. On 27psi, the car ran an 8.33@163mph – a new PB! 

With the pre-event R&D a raging success and the Val’s 60-foot times finally where they needed to be – not to mention running a new PB – it was time to load POR440 up and head to Drag Challenge to contest the Pro Street Radials 8.5 Radial index class! Next month, I’ll tell you all about how we went, or check out the video below!