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Old 05-17-2010, 03:08 PM
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cam duration question

This may be a stupid question... In general, is a cam with a longer or shorter duration better for drag racing?

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Old 05-17-2010, 03:28 PM
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Longer duration camshafts are used in drag racing motors.

The numbers might change a little depending who you ask but cams with more than 245-255 degrees duration at .050" aren't usually put in street-driven vehicles.
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Old 05-17-2010, 03:33 PM
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ok. and one more question: Some cams say that you have to run a certain rpm stall converter, but what happens if you use the stock converter instead of one with higher stall speed?
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Old 05-17-2010, 05:06 PM
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Quote:
Originally Posted by bigdog7373
ok. and one more question: Some cams say that you have to run a certain rpm stall converter, but what happens if you use the stock converter instead of one with higher stall speed?
Any cam you bolt into the motor will have an effective operating range (a range of rpm's where it works well) of about 3500 rpm's. In other words, it will be effective from idle to 4250 or from 1500 to 5000 or from 3000 to 6500 or from 5000 to 8500 or whatever. A cam that is ground to operate efficiently at 3000 to 6500 will make very little power under 3000. If you are using a converter that locks up at, for instance, 1200 rpm's, then the motor is going to be lugging along, gasping, for the span of rpm's between 1200 and 3000. A kid on a bicycle may be able to beat you in the first 100 feet. This is an over-simplification, but I hope you get the idea. Now, if you were to use the 3000-6500 cam with a converter that stalls at or over 3000 rpm's, then when you wood the throttle, the rpm's would zing up to 3000, the motor would make good power from there until 6500 and all would be right with the world.

A converter that stalls at around 3000 rpm's will work fine on the street, although you would want to add a good air to fluid cooler in front of the radiator to remove the additional heat generated by the higher slippage in the converter.

Last edited by techinspector1; 05-17-2010 at 05:13 PM.
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Old 05-17-2010, 09:45 PM
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so what would be a good duration for mostly street driving, and some drag racing every once in a while, without having to upgrade from the stock converter but still have more power than stock cam?
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