How To Decide On A Camshaft
First, let me explain how the camshaft lobe works in the easiest terms. What you will be looking at when you go to purchase a camshaft are lift and duration, the lift is how much the valve opens and duration is how long it stays open both of the together regulate the air and fuel that get delivered to your engine.
The higher the lift the bigger the shot of air and fuel and the longer the valve stays open the longer the fuel delivered and the bigger the boom IE more performance. If you match the cam to you other fuel system components it will do wonders for your performance.
However, there are caveats if you drive your car on the street. If you run a big cam and an automatic transmission you may need a stall converter to your you engine to launch in the power band of the cam.
This is not needed if you have a car with a standard transmission.
The specs below are for a common high-performance small block Chevy engine known as an LT1.
3927140 1st optional
Lift @0 lash Int .492, Ex .512
Valve timing: Intake
Open BTC 53*
close ABC 100*
open @bbc 101*
closing @ ATC 65*
duration overlap 346*
These are the specs for a 1970 LT 1 350 CID / 375 HP. They were typically underrated in horsepower from the factory for insurance reasons. With this setup, you’d need a 2500 rpm stall converter with an automatic transmission.
Because the cam rpm range started at 2500 rpm.
It does take some knowledge to make an engine perform the way that you want it to. Especially when you plan to drive the car on the street.
It’s no secret that the more power you wring out of an engine the less street friendly it becomes so you have to aim for a sweet spot.
This is an area where you are satisfied with the power it has, and you like the way it drives on the street. It is truly a fine line between the two. Back in the day, this engine had an 11:1 compression ratio but they also had high-grade fuels that you could buy.
The more compression you get the higher octane you will need, and yes you can buy fuel at the performance shop in your city.
But back in the day, they had 100+ octane at the pump. To get the performance out of the engine you’d need to be able to put up with the lopety lope of the big cam.