. . .not good on an engine that is going to see street use.
This came up yesterday so I thought I would elaborate a little. Couple of things first?
Can adding duration to a camshaft make up for limited lift? Answer is yes.
Will it affect my HP? Peak power no, Power band yes.
Will its street manners be affected? Yes
For years stockers have been limited by lift rules. So duration was added to lobes. Please Harold confirm this but I have been told that in the early '70's when the Buicks were running John Reed and Harold Brookshire came out with the "launcher". Buicks were handicapped by very low lift numbers so a RECTANGLE lobe was designed by Harold and John to "launch" the lifter. Duration on this beast was incredible and they didn't last long but man could you turn those GS's to the moon because they made power up stairs.
You can add duration to make up for limiting lift factors in your combo. You still should be able to reach your peak power numbers, BUT your power band is going to be narrowed considerable. If the optimum cam was going to make a powerband that was within 10% of peak on either side of the curve for a range of 2000 rpm, then the cam with more duration and less lift may make 10% of peak power for only 1200 rpm. Now you have a narrower window of power to operate in. Which means gear selection in both rear and trany are critical.
Also when you narrow up the powerband you increase the work the engine has to do to accellerate. Think of it this way, a nice flat power band that is 2000 rpm wide and and around 6% of peak at either end is like you walking on land with a 1% incline and a 75# pack. It's work but not that bad. A narrow power band that is within 10% of peak that is 1200 rpm wide is like walking up a 10% incline with the same 75# pack. You can do it but your going to be slower because it takes more energy to climb.
Now do the latter but without the pack. Hey it is a little quicker but maybe not as quick as the flatter powerband. This is where cam companies say with a lighter car you can run a "bigger" cam because during accelleration the engine is not having to move as much mass.
In some forms of racing where the engine operates in a narrow powerband (Pro Stock) you want to cam for a narrow band because the engine isn't going to operate out of it. In a street strip application like most here are doing you want a nice fat powerband so that the engine can has a good average power over a broad rpm band.
I hope my simple ways of explaining this helps.
This came up yesterday so I thought I would elaborate a little. Couple of things first?
Can adding duration to a camshaft make up for limited lift? Answer is yes.
Will it affect my HP? Peak power no, Power band yes.
Will its street manners be affected? Yes
For years stockers have been limited by lift rules. So duration was added to lobes. Please Harold confirm this but I have been told that in the early '70's when the Buicks were running John Reed and Harold Brookshire came out with the "launcher". Buicks were handicapped by very low lift numbers so a RECTANGLE lobe was designed by Harold and John to "launch" the lifter. Duration on this beast was incredible and they didn't last long but man could you turn those GS's to the moon because they made power up stairs.
You can add duration to make up for limiting lift factors in your combo. You still should be able to reach your peak power numbers, BUT your power band is going to be narrowed considerable. If the optimum cam was going to make a powerband that was within 10% of peak on either side of the curve for a range of 2000 rpm, then the cam with more duration and less lift may make 10% of peak power for only 1200 rpm. Now you have a narrower window of power to operate in. Which means gear selection in both rear and trany are critical.
Also when you narrow up the powerband you increase the work the engine has to do to accellerate. Think of it this way, a nice flat power band that is 2000 rpm wide and and around 6% of peak at either end is like you walking on land with a 1% incline and a 75# pack. It's work but not that bad. A narrow power band that is within 10% of peak that is 1200 rpm wide is like walking up a 10% incline with the same 75# pack. You can do it but your going to be slower because it takes more energy to climb.
Now do the latter but without the pack. Hey it is a little quicker but maybe not as quick as the flatter powerband. This is where cam companies say with a lighter car you can run a "bigger" cam because during accelleration the engine is not having to move as much mass.
In some forms of racing where the engine operates in a narrow powerband (Pro Stock) you want to cam for a narrow band because the engine isn't going to operate out of it. In a street strip application like most here are doing you want a nice fat powerband so that the engine can has a good average power over a broad rpm band.
I hope my simple ways of explaining this helps.
