Posted by Brian in Oregon on August 18, 2000 at 01:12:35:
In Reply to: rebuilding '67 318ci motor, and need advice. posted by Jonas on August 18, 2000 at 00:14:28:
Engines pick up more power from:
Increased breathing, which is further broken down into intake and exhaust. The easier it is to get air and fuel in, and exhaust out, the more power you'll make. There is a point where you can increase power w/o increasing fuel consumption, but it is very easy to go past that point and create a gas guzzler, albeit a fast gas guzzler. For the most part, better exhaust helps flow and is usually more restrictive than the intake side, and usually doesn't increase fuel consumption much, if at all, and often increases gas mileage.
Higher compression. It's simple, the more compression, the more power. Drawbacks - more heat, more stress on motor, possible need for higher octane fuel (read - $$$).
If this is a daily driver, I'd put on a mild easier breathing intake manifold, a dual plane if possible for good low end torque; a mild "rv" grind or modest performance cam; and dual exhaust. I'd leave the compression ratio alone, unless you want to risk needing higher octane fuel. Don't put a huge carb on.
If you run a cam warmer than an rv cam, you might wish to run a Cloyes True Roller timing chain and advance the cam either 2 or preferably 4 degrees. This moves the torque range down to a lower RPM. This works quite well on engines not designed for all out breathing at high RPM, or those not stressed for high RPM running. I used this trick to very good advantage in the stock classes at the drags. Rather than buzzing the motor to make power, I made my power coming off the line and launched harder. Those who put in big cams and ran them straight up or even retarded them could not use all the power they provided as they ran out of breathing, or comp9onents (rods, etc) stressed to take those rpms. in other words, the peak torque range was beyond the safe limit of the engine.