What is a good RPM range for a muscle car?
Although some cam grinders will tell you that their cams will have an operating range over a span of 4000 or even 4500 rpm's, realistically the true effective range is about 3500 rpm's. It'll make good power from 1000 to 4500 or from 1500 to 5000 or from 2000 to 5500 or from 2500 to 6000, etc., etc.
A lot of the cams I am seeing have a operating range that start around 2500RPM or higher. That seems really high to me for a street car.
I think 2500 to 6000 is realistic. You could run a manual trans with it or you could run a 3000/3500 stall torque converter with an automatic which would allow the motor to come up in revs and "get up on the cam" to move the car. With a manual trans, you just slip the clutch a little and rev the motor a little when moving from a standing stop. Any cam you bolt into the motor will have its good points and its bad points. There is no "one size fits all".
Does the operating range of a cam dictate the idle speed of the engine as well?
Yes, as the grind becomes wilder, the idle speed will have to move up. A lope is simply the sound of a motor being inefficient. It is the sound of a motor with a cam that is too large to be operated at a low rpm. What happens is that the intake closing point on the cam is extended with a hot cam, to the point that the intake valve does not close until the piston is well up in the bore on the compression stroke. This allows the piston to push some of the mixture that has just been drawn through the carburetor and into the cylinder.....back out of the cylinder and back up the intake tract, past the venturi again and back out the top of the carburetor body. You can see this phenomenon, known as standoff, at night under a strong light shone on the carburetor. As the fuel slug is pushed back out the carburetor, it passes the venturi again, just like it did going into the motor. The venturi doesn't care which way the fuel slug is going, it sees a depression and adds fuel to the slug. Then, on the next intake stroke of the motor, the fuel/air slug is sucked back down into the motor and.......yep......you guessed it, the venturi adds more fuel. Well, by this time, the slug is waaaaaaay rich and the motor cannot idle cleanly. This is why you will see heavily cammed motors going rump, rump, rump and why the car owner has to continually blip the throttle to clean out the motor so that it will continue to idle. Otherwise, if left alone, the motor will load up with fuel and die.
If the operating range of a cam was 2500-6500 RPM. Does that mean the idle speed has to be around 2500 RPM?
No. Normally, with a stock cam, you will be idling around 600 rpm's. As you go wilder with the grind, you will have to move up to 700, 800, 900 or maybe 1000 rpm's because the cam just will not idle cleanly at a lower rpm.
Back when I was a kid, we used to idle through Shoney's with the choke on to make the motor rump-rump. hahahahahahahaha
Or is that just the range that it starts to produce power.
A cam that makes power from 2500 to 6000 won't make enough power to pull the hat off your head under 1000. This is just my opinion and has no scientific fact attached.
Would I be hurting the engine if it is below the intended operating range?
You won't hurt the motor or the cam, but you won't be doing fuel mileage any good. This is one of the things I try to impress on fellows who plan to use an overdrive transmission and cruise at 2000. If the operating range of the cam if 2500 to 6000, then you are just kidding yourself that you're going to make additional mileage with that hot cam. Nothing could be further from the truth. You should have used a cam that makes power from 1200 to 4700, so that it's "up on the cam" and in its efficiency zone by 2000.
Also, if the operating range of a cam is higher, does that mean the car is harder to drive with a stick. Like is it hard to pull out from a stop if the operating range is higher than normal?
It takes a little getting used to. You just rev the motor a little higher and slip the clutch a little more.
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