So, I got a trio of 97's on an Offy intake on a hot flathead Ford. They are set up for methanol on a FED. I have a scoop on top of the carbs to get some ram air effect at speed. I have recently heard that 97's don't like to be fed with a ram air and would run better with a bread box over the top of them. Has anyone heard of this before or had any experience with this matter?
I think the box would be better= still air, instead of an awkward stream blowing past. The faster you go, the more violent the stream becomes.....I might be full of it, but it has been tried and true'd. At least shield the tops.... The guys at FB wouldn't take kindly to your Q, But I get it. Hunt around here a lil, and you will find your answer.....
Strombergs do their best work gathering air from a non-turbulent, non-restrictive dead air space. If you're using scoops, turn them to the rear. Also, contrary to the old thinking of removing the chokeplates for "more flow", it has been dyno proven that leaving them in place allows a smooth airstream over the open ends of the discharge jets for proper venturi signal and atomization of the fuel. You might actually pick up 2 or 3 horsepower. Not to mention the added luxury and bonus of not siphoning fuel at speeds in excess of 200 mph!
The ram effect from a scoop is quite small, at 200mph the best you can get if the speed is converted perfectly to pressure is about a 5% increase in pressure, at half the speed the effect is only a quarter of that, i.e. max ~1,25% pressure increase at 100mph. And as I said, that's the perfect scenario that you get on a F1 race car after alot of simulation and wind tunnel testing, a scoop simply designed to fit where there's room for it or to look good will probably be nowhere close to that. Worse still, it probably causes alot of turbulence inside the scoop, making the carburettor work under changing conditions all the time, possibly making it impossible to get a consistent fuel amount. Most of the so called scoops I've seen on hotrods don't deserve that name. A scoop needs to be relatively big, and designed with a relatively small opening facing forwards located in free stream air (not disturbed by the radiator etc.), gradually increasing in size the further the air gets inside it so it slows down and the pressure goes up. You don't up the pressure by trying to jam air into a "funnel", most of it will just go around the edges anyway, you increase pressure by converting the momentum the air has as it enters gradually to pressure by carefully making it slow down.
i have run then both ways. turned forward the gas was sucked out of the carbs and splashed on the windshield. reversing them stopped that. this happened when the speeds were over 70 mph.
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