Glenn Torrens runs the rollers to prise some power from his VW's modified motor
My brown Beetle was screwed together from a $750 backyard-buy body and a stack of other VW bits I had laying around. The body’s little spots of rust were repaired and, while everything was bare, I reinforced the body by stitch-welding its seams.
That process added extra strength for possible motorsport or off-road/outback charity trek use.
You wanna go really, really fast? You need to be singing the right tune. Naturally, I’ve had my salt-lake Bug on the dyno, too
After the welding, the entire interior and underside of the body was freshened with new Savanna Beige paint, leaving the exterior of the car tatty-but-original.
I like the look of proper patina! Inside, I installed Mazda MX-5 bucket seats and ‘minimalist’ trim. The seats are quite light – Mazda had a mantra of minimum mass when mapping-out its magic little MX-5 – and the headlining and carpet I fitted weigh about the same as a box of tissues.
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These Kadron carbies have one throat feeding the two cylinder runners and are a great upgrade for a street-driven VW
Out the back, I fitted a fiery flat-four engine built by respected engine man Stan Pobjoy. It’s a 1916cc donk based on a 1970s VW Super Bug case/block and as well as bigger-bore set of pistons, has a specially counterweighted crankshaft and performance camshaft for running to 7000rpm. To make the most of all that, the cylinder heads are aftermarket castings for plenty more air flow and therefore plenty more power.
When the motor was fitted, at first I installed a pair of single-throat carbies known as Kadrons. These simple, durable and reliable carbies are similar to those used on classic four-cylinder Porsches and since the 1980s, these have been popular on modified VW motors around the world. They are available in two versions, 40 and 44, with the numbers telling of the throat size. Most VW motors are happy with the smaller version however I knew my engine’s output would possibly benefit from the Kadron 44s.
Luckily, years ago, I bought a set of the 44s and dyno- tuned them for a similar 1916cc engine that fellow UC contributor Dave Morley and I raced at the 2011 Australian Hill Climb Championship (jeez – was it that long ago?!) in my now-sold yellow VW Beetle hill climb/tarmac rally car.
Anyway, it was these dyno-tweaked 44mm carbs that I first used on the freshly built 1916cc engine in my ‘new’ brown Bug. I used these carbs for a couple of thousand road kays, and to have some fun at the 2019 Taree Airport Drags event after I completed the car.
But I also knew there was even more power potential in a set of dual-throat (so, with two carbs on a four cylinder engine, one throat per cylinder) Weber carburettors.
As with most carburettors, the Webers would be best ‘dialled-in’ on a chassis dynamometer to make sure the jets – and therefore the fuel mixture – was correct for the engine.
Off with the Kadrons and on with the Webers. These have two throats each, one dedicated throat per cylinder can provide a tuning/power advantage but only if the engine can use it
So I booked some dyno time at my local grunt-hunt shop, G-Force Performance Centre, to tune the Webers. Based on his decades of experience, my engine builder Stan suggested a ‘baseline’ jet spec that I could go up or down from depending on what the dyno revealed. The G-Force dyno bloke, Glenn – who often works on 500+hp V8s – concurred and we spun the rollers to see what my Bug’s motor was doing.
With a bit of disciplined fiddling, we found the jet size that resulted in maximum power for my engine. I won’t bore you with all the processes and numbers but this snappy 1916cc has about three times the power of a standard VW motor and with less than 850kg to push around (with me in it!) it’s good fun!
Wrong fuel mixtures can not only deprive an engine of power, but cause drivability problems, and in extreme cases, engine damage!
Next, I’ll run it at Sydney’s 400m drag strip to answer the question of “what’ll she do, mate?”
From Unique Cars #470, Sep/Oct 2022