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Old 04-20-2011, 10:03 AM
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bobcowan bobcowan is offline
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Join Date: Feb 2007
Location: Colorado Springs, CO
Cobra Make, Engine: Backdraft, supercharged Coyote
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Sounds like you dodged a bullet on that one!

As for the engine, a lot depends on what you plan on doing with it. Unless the car dedicated to a specific purpose, everythings a bit of a comprimise.

Any stack system (EFI or Webers) will cost you a bit at the top end. Without a common plenum, it's a little more difficult to force feed the cylinders. But, you get greats looks instead. If I was building a dedicated track car, I would not use stacks or webers. But for a street or mixed use car I think they're awesome.

EFI is the way to go, IMO. Nothing like modern technology to make your life easier. I live at 6,400' ASL. My car runs just as well at 10,000' ASL in cold weather as it does at 4,500' ASL in hot weather. The computer senses the changes and adjusts accordingly. Last year we raced in Tulsa, 850' ASL. We didn't have to make any changes at all. Drove it off the trailer and onto the track. Computer did it all for us; and the car ran great all week end.

Fine tuning is pretty simple. Connect a lap top and tap a few keys. No buying jets, emulsion tubes, choke tubes, etc. You can make changes while your strapped in and driving down the highway. The newer systems use a wide band O2 sensor, so the computer makes those adjustments for you. Regardless of the system, the initial tune should be done on the eddy dyno with an experianced tuner.

Selection of cam and heads is critical with stacks. If the heads and valves are too big, you lose intake velocity and your low end power drops like a stone. The wrong filters can cost you a lot of power, too. The traditional tea strainers cost me 100hp on the dyno.

The camshaft can be a little tricky, too. A wider LSA will really reduce reversion and increase chamber filling. Simply increasing the LSA will give more power and efficiency.

I use a cam that pretty big - just about the biggest hydraulic roller in the comp cams catalog, with 114* LSA. Makes excellent power, a very flat torque curve, and drives around town with not trouble at all. The car is easy and fun to drive on the street, with no bad manners. But when you mash the throttle, it screams like a banshee and takes off like a rocket. It's easy to drive on the track because the torque curve is so flat; I generally use only 3rd and 4th gears. Last week end I shifted only twice per lap- once from 3rd to 4th, and again from 4th to 3rd.
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