When looking at cams, they are usually listed with the
advertised duration measured @.006 tappet lift and the duration
@.050. The comparison of the two durations will show the ramp speed
or intensity of the cam lobe.
An example of a slow ramp cam would be the Edelbrock Performer
cam for the 351c, it has an advertised duration of 282int/292ex, but
the duration @.050 is only 204int/214ex. This cam has a very slow
action to it.
An exapme of a fast ramp cam would be an Ultradyne Cam I was
looking at, it had a 276int/276ex for advertised duration and the
duration @.050 was 221int/221ex. This is a fairly fast ramp for a
hydraulic lifter cam.
The comparison of these two cams is in the single lobes, not the
comparison of single pattern versus dual pattern cam. Ultradyne
appears to no longer be in business.
I feel that the fast ramp would give you "the best of both
worlds" so to speak. In the way of it having the smaller advertised
duration close to stock cam status, but with the .050 duration closer
to a high performance cam. The longer "open" time would provide more
air flow, yet still have the drivability because the "closed" time is
near that of a stock cam. The bad effect of a fast ramp is with the
higher intensity, rate of wear will increase and the longevity is
reduced.
Now other then the longevity from an "easy on parts" slow ramp,
what application would a slow ramp be better suited in then a fast
ramp? I am wondering which profile would be better for say big or
small exhaust, big or small ports, or big or small carbs? How would
the ramp speed compliment the resonance of the air/fuel charge with
the different big/small ports, exhaust, and intake?
Cam companies make both style cams, they have big cams in fast
and slow ramps and small cams in fast and slow ramps. That leads me
to believe that application would determine one over the other. I'd
think the focus would be to have the valve move faster, so more time
can be spent in the open time without reducing the closed time and
spend less time getting to either in the transition time. It seems
the trend is to make the ramps faster, but the slow ramps are not
outdated and still widely offered by many cam companies---which leads
me up to this question.
Let me know what you think,
Mark Piechowski
70 XR-7 460 AOD
69 SS 351c 2v AOD
70 XR-7 conv 351c 4v FMX
69 Sunroof Eliminator 351w 4v FMX
advertised duration measured @.006 tappet lift and the duration
@.050. The comparison of the two durations will show the ramp speed
or intensity of the cam lobe.
An example of a slow ramp cam would be the Edelbrock Performer
cam for the 351c, it has an advertised duration of 282int/292ex, but
the duration @.050 is only 204int/214ex. This cam has a very slow
action to it.
An exapme of a fast ramp cam would be an Ultradyne Cam I was
looking at, it had a 276int/276ex for advertised duration and the
duration @.050 was 221int/221ex. This is a fairly fast ramp for a
hydraulic lifter cam.
The comparison of these two cams is in the single lobes, not the
comparison of single pattern versus dual pattern cam. Ultradyne
appears to no longer be in business.
I feel that the fast ramp would give you "the best of both
worlds" so to speak. In the way of it having the smaller advertised
duration close to stock cam status, but with the .050 duration closer
to a high performance cam. The longer "open" time would provide more
air flow, yet still have the drivability because the "closed" time is
near that of a stock cam. The bad effect of a fast ramp is with the
higher intensity, rate of wear will increase and the longevity is
reduced.
Now other then the longevity from an "easy on parts" slow ramp,
what application would a slow ramp be better suited in then a fast
ramp? I am wondering which profile would be better for say big or
small exhaust, big or small ports, or big or small carbs? How would
the ramp speed compliment the resonance of the air/fuel charge with
the different big/small ports, exhaust, and intake?
Cam companies make both style cams, they have big cams in fast
and slow ramps and small cams in fast and slow ramps. That leads me
to believe that application would determine one over the other. I'd
think the focus would be to have the valve move faster, so more time
can be spent in the open time without reducing the closed time and
spend less time getting to either in the transition time. It seems
the trend is to make the ramps faster, but the slow ramps are not
outdated and still widely offered by many cam companies---which leads
me up to this question.
Let me know what you think,
Mark Piechowski
70 XR-7 460 AOD
69 SS 351c 2v AOD
70 XR-7 conv 351c 4v FMX
69 Sunroof Eliminator 351w 4v FMX