Getting More Power from a Chrysler 318 V8
Guidelines for the first time 318 builder
Over camming and over carbing, and just plain over building, has been more frustating to more people than you would imagine. If you`re going to try to build that 318, do yourself a favor and figure out just what it is that you want from this engine. There is a big difference between a street engine and a race engine, and driving a car with poor street manners can be little fun at all.
Stick with a 600 or 650 vacuum secondaries carb and a dual plane intake such as the Edelbrock Performer. Avoid single plane intakes and 700+ cfm carb, which is too big for a street motor and bad on gas.
Camshaft
Cams that start making power above 2500 rpms aren't very good in heavy cars because getting a 3500-4200 lb. vehicle to take off takes a lot of torque (unless it's geared REAL steep). A cam that starts making power off idle to 3500-4500 rpms would be good for a daily driver. But, if you spend most of your time above 3500-4000rpms, get a bigger cam that's made to operate in those rpms.
A .455" lift cam is not at all radical. I'm basing this on the fact that the stock cam in a 318 has .400 lift, a stock 360 has .410 lift and the Performer cam from the excellent folks at Edelbrock has a lift of .420" and duration @.050 of .204". The cam from Mopar has been superceded by P4452761 and has about the same duration as the cam from Edelbrock, w/.450/.455 lift, meaning a similar powerband with more power throughout. Remember, a cam that is large for a 318 is just right for a 360 due to the cubic inch difference.
Exhaust
Consider headers and dual exhaust a must.
Cylinder Heads
The is a catch-22 for the average garage-dweller. The 318 head flow less than a set of 360 heads, but the 360 heads lower the compression ratio below what the 318 original had.
However, finding a good set of 360 heads with an good cam would probably work wonders with a small 4bbl carburator. You won't need a set of race heads, even the smaller valve 360 heads will work wonders over the poor 318 heads.
Outside the Engine Bay
If you can afford steeper gears, going from 2.76s to 3.23s would boost performance without hurting gas mileage too much, and generally help out in the "seat" feeling. 3.55s and steeper would give you better acceleration, but at the expense of top speed and gas mileage. On a daily driver, don't over gear!