While I’ve tangoed with turbos, I’m a blower guy at heart, so I decided to add a supercharger to a little 4.8-litre LS that I had sitting in the corner of my shed and see how far I could push it on a budget. 

The LS in question was hardly a hot-ticket item, as the bigger-cube versions are generally picked first for the prom before these little truck motors. But a bunch of searching on YouTube failed to uncover anyone who’d done any real horsepower testing on a Roots-blown, stock-bottom-end (SBE) 4.8-litre LS, so my little mill offered the ideal opportunity to take the road less travelled and build a low-buck, big-boost, 6/71-blown combo that would sing like a canary. 

First published in the July 2026 issue of Street Machine

I began to ponder how cheaply you could build a bottom-of-the-food-chain 4.8-litre, and how much power you could make both on E85 and alcohol. With the more aggressive tune-ups those fuels allow, I figured I could build something that would work for burnouts, drag-and-drive, or something spicy for a street car, and potentially produce big numbers.

The 4.8 was a 260,000-mile wrecker motor from the US that owed me under $1500. The plan was pretty simple: blow it apart, wash it up and assemble it with all-factory parts, with the exception of the camshaft, valve springs, pushrods and ARP head bolts (I opted for head bolts over studs to keep the cost down).

I was aiming to make 800hp for under $14,000 with mechanical injection on alcohol, and for under 12 grand with a carby set-up on E85. It was a tall order, but with the engine parts being stock, estimating the cost of building such a combo was pretty easy. It was the extras like the blower, hat, carbs and fuel system that would take some wrangling on Marketplace to keep it all under budget.

First, I pulled the mill apart and hit the cylinder bores with the flex hone, and after reassembling the engine and getting 13-14 per cent leakdown on the original rings, I blew it apart again and fitted new rings with .0024in of ring gap on the top ring and .0022in on the second. 

With a few minor exceptions, I bought all the engine parts from Crow Cams, and spoke to their tech guys, Rob and Alex, about designing a cam we call ‘Maximus’. It’s the biggest blower cam they could fit into this engine without running into piston-to-valve clearance issues.

The boys at BG Engines in Sydney’s north-west did a quick overhaul on the 243/799 cathedral-port heads that came with the engine, which are the same heads found on 6.0-litre LS2s in Australia.

The engine runs a single-row timing chain, and the oil pump has been upgraded to a Melling high-volume jobbie. The cam bearings were worn, and still are – nobody likes to mess with those things! A new set of pushrods needed to be ordered to get preload right, .660in valve springs were used, and the rockers are still the tired old factory ones that will eventually get a trunnion upgrade when a set appears on Marketplace for the right price.

The real spend for the project was in the blower set-up, and again Marketplace was our friend here. A pair of boost-referenced 750 Quick Fuel carbs, 2×4 carb plate, stock 6/71 blower, intake, blower belt, pulleys, blower idler, water pump, and an old Enderle bug hat were all sourced when the price was right. 

Sydney blower guru Jeff Ramsay from Jeff Ramsay Engineering gave the Detroit supercharger the once-over and made a blower snout to suit the pulley offset.

Although I probably could have done without the expense, I fitted a front crank support, as I was looking for longevity, should it survive the dyno.

The fuel pump drive and the crank support with 6PK serpentine drive for the alternator and water pump were the two biggest expenses. Ditch the crank support and make your own fuel pump mount and you could shave $3000 off the build price!

With the engine all buttoned up, we loaded it on the dyno at BG Engines. After a glitch with the O-ring on the pick-up tube stopping us from getting oil pressure, it was all systems go.

Well, almost. It turned out that the second-hand E85 carbs were suffering from sitting around for a year and had frozen accelerator pumps, so Damian Baker – our trusty jack-of-all-trades, dyno operator and co-owner of BG Engines with Mick Green – gave them a quick once-over. Then we were ready to get some kind of number with the carbies before stepping things up.

On the ignition side, an MSD 6LS was uploaded with 18 degrees of timing across the board, and the overdrive on the 6/71 was set at 13 per cent, which was predicted to make 20psi of boost – a bit of a gutsy call straight-up.

With the plan to step the tune up on alcohol – the fuel of choice for any serious activities – we wanted to get a number on the board with E85 in case things went to mud later.

This is not the type of thing BG Engines usually gets involved with – after all, they are one of Sydney’s premier engine building shops. But they do have a dyno and a lot of tuning experience, so despite his trepidation, Damo made the first pull on E85, which threw our early horsepower guestimates out the window, with the little LS pumping out 733hp at 6600rpm on 19psi of boost! And with that, we had our street tune!

We could have kept leaning on what the plugs showed to be a pretty safe tune, but E85 was never going to get us where we wanted to go. It was time to step it up and make the change to alcohol, and we decided to stick with the tune as it was.

Unfortunately, our second-hand injector hat had someone smarter than the manufacturer mess with the barrel valve and fuel scroll, and we just couldn’t get the leakdown anywhere near 65 per cent to get started. The only option was to pull parts off other injector hats in the workshop to make mine work. A bunch of barrel valves were mixed and matched, and while we eventually got the leakdown right, each time we cracked the throttle to load the motor up, the fuel pressure would drop and it would go lean. Two pumps and hours of trying with multiple barrel valve parts couldn’t fix the lean stumble off idle.

We managed to work around the stumble and give the mill its first pull on alcohol to 6700rpm, and it belted out 838hp and 19psi of boost with 18 degrees of timing – we were up more than 100hp just by changing fuel. On the next run, we turned it a little harder to 7000rpm, and it sounded killer while making 888hp!

However, we still wanted that magical 900hp. Some of the boys took the 888 as an omen to stop, but the timing strap was barely visible on the sparkplug, so we added another degree, buzzing it to 7300rpm and only picking up 3hp. Clearly, it didn’t want timing, so we decided to make a pill change and knock the main pill back .0005in to take a little fuel out. Boom – 919.5hp at 7300rpm on 22psi of boost, and a whopping 751lb-ft of torque. What a monster!

That’s a whole bunch of whoop-arse from not a lot of motor. We toyed with the idea of trying to get 950 out of it, but it was running so sweet that it would have been silly to push it further and risk binning the whole deal. I think it would have done it with more boost, but we were happy to high-five and pull a nice, running motor off the dyno with a 919.5hp scorecard.

I’d like to report that it fought us all the way, but it really didn’t; it sailed into the 900s and sounded sweet all the way. To top the day off, the oil filter was clean, it didn’t breathe out of the valve covers at all, and it’s now ready to bust some moves in a car.

Big shout-out the BG Engines team, the boys at Crow Cams for their awesome ‘Maximus’ cam, and Jeff Ramsay Engineering.  

BUILD COST: stock-bottom-end

4.8-litre LS