STAGE WRITE
SOME of you may have noticed that many of the quick naturally aspirated cars featured in Street Machine are running Ray Edwards carbs. Recently Garry Hunt was testing a freshly rebuilt LS street engine for his nine-second VB Commodore on Lionel Durre’s dyno in Yeppoon, and Ray Edwards was coming up from Brisbane to calibrate Garry’s 1050 RAYJE five-circuit Pro Stock carb with several different drums of VP, Sunoco and ETS racing fuels. It was a great opportunity for me to meet Ray, the mysterious quiet achiever who never advertises; word of mouth sees customers lining up for Ray’s beautifully machined fourbarrel carbs.
Ray’s carbs are not just great for horsepower but are especially good for events like Drag Challenge, where impeccable street manners and good fuel economy are super-important. Besides Garry, Ray’s customers include Tony O’connor, Jai Schluter, Al Vella, Mark Busscher, Bobby Valastro, Frank Marchese, Scott Hipwell and Maritimo Offshore Racing.
Ray’s career kicked off with five years of electrical engineering. Along the way he bought the Super Stock Mules & Higgins Cortina with an injected 292 Ford engine, but ran out of money and sold it. In 1992 he worked for Stewart Knowles at Western Suburbs Performance and started reconditioning carbs there. Nine years later, Ray began importing Advanced Engine Design carbs into Australia, and gained a lot of knowledge when he went to the US to work for AED for a couple of months in 2004. The following year Ray bought his first CNC machine and started
producing his own RAYJE carburettors.
Ray’s carbs start life in Bo Laws kit form, with billet bodies that only have pilot holes. Ray then re-does all the metering to his own specs. He can machine a 4150 legal body to 1450cfm, and a 4500-series carb to just under 3000cfm. Ray also modifies a basic threecircuit carb into a five-circuit Pro Stock-type carb. Essentially, anything a US carb company can do, Ray can do here in Australia. One of the obvious advantages of a Ray Edwards-built carb is that it can be fixed and calibrated here.
The secret everyone wants to know is: How does one of Ray’s carburettors make 50hp more than another carburettor that flows identical cfm with both carbs jetted to give a 12.8:1 air/fuel ratio? In a nutshell, it is all about matching the right-size carb to the engine and optimising the aerosol properties of the fuel being used.
Let’s start with some fundamentals. To make a naturally aspirated engine exceed 100 per cent volumetric efficiency, you need high air speed. The carb size needs to be big enough so it’s not a restriction but small enough so when you shift gears it still atomises correctly – this is called shift recovery. Next you need the air/fuel mix to be as dense as possible for maximum ram inertia effect. You want the right-size droplets of fuel in the intake charge. Fuel expands to 16 times its volume when it vaporises to a gas, and you lose ram charge if it becomes a gas from being over-atomised. It sounds crazy, but it shows up on the dyno like some sort of witchcraft.
When Ray opened up his magic box of trick carb bits while chasing the tune on Garry’s new combo, I noticed a bunch of changeable boosters – some with lots of small holes, other with a lot fewer but bigger holes – as well as his own machined super-accurate jets. Calibrating a carb on the dyno is no five-minute job. The procedure is very time-consuming and is often a case of ‘two steps forward and one step back’. Timing and jetting changes are made for a baseline with an air/fuel ratio of 12.8:1. When different boosters are tried the a/f ratio can go lean or rich, which requires re-jetting to bring the ratio back to 12.8:1. Then the timing needs to be retested to make sure it’s optimal for the fuel used.
On Garry’s motor there was a jaw-dropping 40hp difference in power between the best and worst fuel, but the testing wasn’t conclusive enough to publish the results. Garry and Ray ran out of dyno time, and there appeared to be some sort of restriction in the new 440-cube LS engine combo. The dyno curve was climbing beautifully making 900hp at 7700rpm, and then flatlined up to 8600rpm like there was a restriction or something else wrong with the combo. Garry was thinking he may have to revisit the dyno with a bigger set of pipes or another camshaft.
The bottom line is, Garry’s freshened-up cast-iron LS motor came off Lionel Durre’s dyno with 900hp. Garry’s VB Commodore weighs in at 3100lb, so that elusive eightsecond pass he’s been chasing for some time should be only a formality, as the street sleeper should be capable of 8.7s at 156mph according to the Moroso calculator. That’s a pretty tough single-four-barrel, naturally aspirated streeter.
RAY EDWARDS’S CARBS ARE NOT JUST GREAT FOR HORSEPOWER BUT ARE ESPECIALLY GOOD FOR EVENTS LIKE DRAG CHALLENGE, WHERE IMPECCABLE STREET MANNERS AND GOOD FUEL ECONOMY ARE SUPER-IMPORTANT