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cam
MetroMPG, the cam specs are more important than most realize. Lift and duration seems to be the BIG info most understand, but OVERLAP and when the Intake Closes make a big difference. Think of it this way; if the intake is still open as the piston moves UP the cylinder, pressure drops lowering compression. The valve needs to be open long enough to fill the cylinder with fuel/air before it closes. Also, with a lot of overlap vacuum suffers, which is used to advance the timing on my points dizzy. I used a TRUCK cam used for pulling in pickups and Vans, putting the maximum torque in the 2000 to 3500 RPM range. I don't remember the duration, lift, overlap, etc. but it worked. The cool-air intake I made pulled air from in front of the radiator, which is about 50 degrees cooler. Say 90 outside, 140 under the hood over the exhaust. Notice I cut an eyebrow-opening on that side of the hood to vent heat also. This is TEXAS so "cold-air intakes do not exist...just cool-air. A denser air charge burns better and Hot Rod magazine proved it even on a stock motor. I make mine out of PVC because metal holds heat. Why pull in cooler air then heat it on the way to the carb? I am an ASE certified mechanic who retired from a city shop as superintendent and was charter president of the Dallas Area Street Rods. Much of my engine knowledge came from being a motorcycle nut for 2 decades as I studied the internal combustion engine.
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