The table below will help you select the right camshaft for your Pontiac
engine. The first column contains the intended use or application category.
(Stock, daily driver, street-strip, etc) The other columns to the right,
contain the intake duration of a cam at .050" lift. Where the application
and camshaft intake duration intersect, I've offered my opinion on whether
a cam with the specified intake duration will complement the intended application.
Each application as you will note, has basic equipment or component requirements
which need to be examined.
pound 1970 GTO, 400 +.030 over, dished pistons, minor porting, 3 angle valve
job, stock 1.5 rockers, stock Q-jet, 3.55 rear gears, 4 speed, dual exhausts;
stock point distributor; used only on the weekends; seldom raced, mostly
for show. Less than 2000 miles per year on the road. Goal: to improve stock
performance but at lower 9.5 to 1 compression to run on pump gasoline. The
engine came with the OEM "S" camshaft (068); 212/225 @.050"
;288/302 advertised duration.
The applicable range in the hypothetical is 210-225; gearing and 4 speed allows for a higher duration so a cam with 220 to 225 intake duration should work pretty well. Note: the bigger the displacement the smoother the idle. Therefore, a 326 with a 220 intake cam will have a very lopey idle in contrast to the same grind working in a 455.
Okay-- see how this works--give it a try.
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