What follows is an in depth carburetor test which was taken from a magazine in 1996. It compares the standard set up usually twin SU HIF6s against the Edelbrock/Weber four barrel,the Holley four barrel and the Burlen Fuel Systems quad-SU conversion. The test was conducted by replacing the entire induction system on a Rover 3.5 V8 which was installed in a Ford Capri . It was judged on both normal road use and on the rolling road at Auto Techniques. So, Would the Holley give big power with big fuel consumption, in the American tradition? Would the Weber live up to the company's reputation? Would the quad-SU kit prove that four single chokes are better are far better than a single four choke? Read on......
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WEBER FOUR BARREL A mass of gleaming chrome and polished ally, the Weber looked the part. It sounded good too, with less induction noise than you would imagine and a pleasing American note.On the rolling road we saw 176bhp and 207lbft - healthy increases of 26% and 4% respectively. On the road the Weber's seamless power delivery of the four-choke was almost on a par with the injected V8 engine, except for a small flat spot very low down in the rev range, which may have been caused by a slightly weak idle mixture. Idling itself was very smooth, and on top of that fuel consumption averaged around 26mpg - a comfortable improvement on the standard 22mpg. |
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HOLLEY FOUR BARREL 165bhp puts the holley just a touch ahead of the quad-SU's, with fuel consumption which is almost equal to the standard set -up and seemed to vary very little with changing conditions. Time and money spent sorting out the primary and secondary jetting on the rolling road would certainly improve power and maybe fuel consumption too,though Auto Technique's Chris Hall reckoned that, as fitted ,the Holley was'nt far off its optimum. Road impressions were mixed . The auto choke did its job well - though it died about a week later. More power than standard? Yes, but delivery's relatively flat until the vacuum operated secondaries open. It revs well, and the torque curve hangs on at higher speeds , suggesting a potential better suited to highly modified V8s.
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QUAD SU,s A favourite with off road racers - because of its ability to keep going when other carbs are starved or flooded the Burlen Fuel Systems quad - SU set up looks the biz....... With this you end up with a class-looking piece of kit. Fire it up and it has its distinct (and loud) sound. The SU-fed Rover rumbles. On the Auto techniques rolling road we recorded 162bhp and 202lbft - solid improvements on the standard spec, but it looked like there was more potential that hadn't been realised. At full throttle the carbs were delivering an over - rich mixture, which wouldn't be helping either power or fuel consumption. the biggest problem, however, was the throttle linkage arrangement. Its quite a complex set - up because the movement at the end of the throttle cable has to operate four carb throttles. On the road it became obvious that a lot of time would have to be spent setting up the linkages to achieve a smooth throttle action. Get it right, though, and you'd probably get more power and better mid - range pick up |
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CONCLUSIONS
The bare figures suggest that the Weber wins hands down. But delve a little deeper and you find a more interesting story. As far as DIY-fit, bolt on, no messing power goes the Weber is certainly a clear leader. Its relatively easy to fit , needs almost no setting up - unless you've got a heavily modified engine - and It provides plenty of grunt.
But the Holley , you could argue looks better both in the car and on the spec sheet. With enough time and effort spent jetting it to match your engine it could also produce something like the Weber's output, though its hard to see it beating the Weber for fuel economy.
The quad - SU Burlen system, on the third hand (?), offers its own set of pros and cons. As we've said already its the only set - up which can cope with the rigours of off road competition. Its also the only one that did'nt smell of petrol as the engine cooled after a run. On top of that, our test mileage showed promising mid - range performance. There's plenty of potential to be exploited there.
So, while all three systems offer your V8 something extra, our money's on the Weber which offers the most complete package by far.
CARBS COMPARED
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KIT
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CARB
AND TYPE
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POWER
BHP
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TORQUE
LBFT
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AVERAGE
MPG
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STANDARD
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2X
SU HIF6
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140
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199
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21.8
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WEBER
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WEBER
FOUR-BARREL
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176
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207
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25.9
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JOHN
WOOLF RACING
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HOLLEY
FOUR BARREL
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165
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182
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21.5
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BURLEN
FUEL SYSTEMS
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4X
SU HIF44
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162
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201
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16.9
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So there you are, a pretty conclusive test I think you'd agree. As to my choice of carb, well my options were cut down to two , the Holley or the Weber ( the rest wouldn't fit under the Westfield bonnet , so I went for the Weber and I haven't regretted it, I'm running it straight out of the box and driven hard it returns 18 - 19 mpg and on a run being careful 27 - 30 mpg.