Supercharging a LS1 by Holden SV8

Supercharging a LS1 by Holden SV8

Blowers sitting miles high out the bonnet are nothing new here in New Zealand; we rarely go an issue without at least one featuring in these pages. However, seeing one bolted to the top of an LS-powered Commodore is rare — in fact, at the time this project was started it was the first in New Zealand. The 2003 SV8 is owned by Kane Rako who, after a few years of ownership, decided he wanted to go blown and enlisted the help of his Uncle Shane and local blower specialist Al Shadwick of Als Blower Drives to undertake the project.

A billet 6-71 now sits atop the LS1 with a pair of Quick Fuel carbs and filters completing that old-school look. It might not have been an easy conversion, but the results are well worth the painstaking amount of work it took to pull it off. So what’s so hard, you ask. Well, unlike the traditional blower onto an SBC conversion — of which Al has completed thousands in his lifetime — the LS conversion was no weekend power-up, especially when going into the crammed Commodore engine bay. It was a tricky affair that required a stack of custom parts, plenty of reshuffling in the engine bay, and a good amount of trial and error. The good news is that Al and Shane have done the legwork so there will be fewer surprises for those who follow.

There were three main areas of difficulty in this conversion, the first being the lack of space in which to fit a three-inch blower drive, the second being the engine accessories offset, and third being the shift from EFI to carb.

Lack of room

The first hurdle to tackle was getting the blower kit bolted onto the engine. Al used a specific kit from The Blower Shop as the blower itself, the billet 6-71, features 6V rotors and is 17mm shorter than a traditional 6-71 — yes, it’s that tight. Despite this, the rear of the bonnet needed notching and spacing back around an inch to clear the back of the blower. The manifold used is a billet twopiece unit and the installation of that at least was very straightforward, as they simply unbolted the old manifold; the billet one is a direct replacement.

Before that new manifold could go on, a few other changes were needed below it. First was the addition of a keyway for the crank, as a non-supercharged LS doesn’t have a keyway. Al used a kit from ATI, which also supplied the blower-specific damper used in the build. The kit contained the specialist gear, including the reamer; the only downside was that it required the front timing cover to be removed so they could drill and ream and crank. On went the ATI Supercharger Super Damper, which doubles the bottom pulley. This gave the alignment offset for the water pump, alternator, and power-steering pump.

If this were being done on a later model LS2 or LS3 engine, the offset of the engine accessories would be OK. In this case, with the engine being an LS1, everything needed to be shifted back half an inch to give clearance between the radiator and engine. The water pump was swapped out for a Corvette pump, which was set back into the motor by a half-inch. This also holds the two tensioners, making that bit easy. Al machined the alternator bracket to get it sitting back the half-inch, and a new KRC power steering pump was set back that half-inch using a custom billet mount. The KRC pump also has a side-mounted reservoir, as the factory-location reservoir was right in the way of where the blower belt would be. On the other side, the water pump suffered a similar fate, being in the way of the blower belt; the top outlet needed to be shifted to mimic that of a truck engine. The pump casting has both pump outlets on it, but one was blanked. Al machined the blanked outlet open and then modified a billet outlet to press into the housing, securing it in place with some Loctite and a grub screw for added security. The old outlet was then machined off, with a billet plug also machined to be pressed in and block the outlet. New radiator hoses were needed.

The final clearancing job concerned the lower blower pulley, as there was no room for the three-inch-wide pulley between the damper and radiator. Al machined a half-inch spacer so the pulley would sit hard against the damper — the kit from The Blower Shop sits it threequarters of an inch out. The radiator was shifted 30mm forward from the stock location, with the lower mounts shifted and brazed into that forward location. This left things tight but workable.

Tricking the Commodore

In an attempt to make the car really old school, Kane opted to go carburetted, which presented another set of challenges. The first was actually an easy hour spent at Western Auto Electrical having all the injection wiring removed from the loom and it tidied up. Any good auto sparky can sort this.

The factory ECU was retained in the build; to achieve this, the TPS also needed to be kept. Al made a bracket that bolts to the carb base plate and holds the sensor onto the back of the butterfly shaft. It is also worth noting that the ’03 was the last of the throttle-cable Commodores; anything newer would require a custom solution using a drive-by wire actuator or the easier route of a pedal conversion.

The fuel system also needed to be modified. Al went back into the machine shop to make a billet dummy fuel pump. This bolts into the factory fuel pump cradle and acts as the pick-up, with submersible hose connected from this to the factory tank plate. That then feeds a 7psi Carter Black fuel pump mounted under the car, which uses the factory fuel pump wiring — modified to suit the location. The factory EFI hardlines were retained — however, if Kane were going for big power these would need to be upgraded. A new braided line in the engine back feeds both the Quick Fuel 680s before going through a Quick Fuel regulator.

The last piece of trickery was setting the timing and modifying the timing map to suit. Darren from Revolution hacked the stock ECU and made all the necessary adjustments — it took nearly a day to get it perfect. Initially, the power increase was a bit of a let-down but the problem was traced to a faulty plug lead, which was replaced; the engine instantly woke up and made more power with less boost. Currently, it’s only running 8psi.

Interestingly, the engine remains almost as Holden built it. The only modifications are a double-row timing chain, valve springs, and a blower cam to suit. We’re told that, with only 8psi, the car now has no issue blowing the tyres off four up. Don’t take our word for it; the fact it’s chewed a few clutches — and rear tyres — should be proof enough. 

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