I need help reading some cam figures...

[StefanLee]

Well, I'm looking to replace my head, and I have found a 1900 head for sale with 46/40 valves and a better-than-original cam in it. The thing is, there are no markings on the cam, so the seller had it measured by a company using Cam Pro Plus.

Here are the charts, including a snazzy graph.

http://i241.photobucket.com/albums/f...nLee/graf1.jpg

http://i241.photobucket.com/albums/f...nLee/graf2.jpg

http://i241.photobucket.com/albums/f...nLee/graf3.jpg

I'm a little confused over the two different cam graphs and charts. I can see intake and exhaust cams, but in two versions and I'm not sure what the low one is. The other lines are cam acceleration, velocity etc...

The lift seems kinda low even on the high cams, from where does the lift measure?

Any help with deciphering this info would be appreciated, I know the readings are in metric but hey you guys are pretty clever...

I'm looking for a cam that is streetable, no point in having a cam that is dead below 4000... How would you rate this cam performance-wise?

Stefan

[RallyBob]

Originally Posted by StefanLee Well, I'm looking to replace my head, and I have found a 1900 head for sale with 46/40 valves and a better-than-original cam in it. The thing is, there are no markings on the cam, so the seller had it measured by a company using Cam Pro Plus. Here are the charts, including a snazzy graph. http://i241.photobucket.com/albums/f...nLee/graf1.jpg http://i241.photobucket.com/albums/f...nLee/graf2.jpg http://i241.photobucket.com/albums/f...nLee/graf3.jpg I'm a little confused over the two different cam graphs and charts. I can see intake and exhaust cams, but in two versions and I'm not sure what the low one is. The other lines are cam acceleration, velocity etc... The lift seems kinda low even on the high cams, from where does the lift measure? Any help with deciphering this info would be appreciated, I know the readings are in metric but hey you guys are pretty clever... I'm looking for a cam that is streetable, no point in having a cam that is dead below 4000... How would you rate this cam performance-wise? Stefan

As near as I can tell, they are rating two different camshafts. The lift is measured at the lobe, not including the rocker arm ratio. So 7.25 mm of lift x 1.5 rocker ratio (approximate) would be 10.875 mm of lift. The 'advertised' duration numbers are not too bad, both cams seem quite streetable, but one has a bit more valve lift than the other.

Bob

[Hiro]

Originally Posted by StefanLee Well, I'm looking to replace my head, and I have found a 1900 head for sale with 46/40 valves and a better-than-original cam in it. The thing is, there are no markings on the cam, so the seller had it measured by a company using Cam Pro Plus. Here are the charts, including a snazzy graph. http://i241.photobucket.com/albums/f...nLee/graf1.jpg http://i241.photobucket.com/albums/f...nLee/graf2.jpg http://i241.photobucket.com/albums/f...nLee/graf3.jpg I'm a little confused over the two different cam graphs and charts. I can see intake and exhaust cams, but in two versions and I'm not sure what the low one is. The other lines are cam acceleration, velocity etc... The lift seems kinda low even on the high cams, from where does the lift measure? Any help with deciphering this info would be appreciated, I know the readings are in metric but hey you guys are pretty clever... I'm looking for a cam that is streetable, no point in having a cam that is dead below 4000... How would you rate this cam performance-wise? Stefan

I think the lower plot shows cam lift & the upper plot shows valve lift,
maybe "E1" is exhaust cam #1 & "I1" is inlet cam #1 from the same camshaft?
in this case there is a slight bias in favor of inlet duration/lift,
this camshaft anyway is not a wild race one so should be OK for street usage.
Hiro

[wrench459]

Help me look into graph 3.
It looks like the top half is the exhaust
and the bottom half is intake
The center line is that projected vacuum readings?

[StefanLee]

Thanks guys, seems reasonable. I did't factor in rocker arm ratio...

wrench459, the other lines are cam velosicty and cam acceleration.

I would also say it looks like two different cams, or as Hiro says that one is modfiied for rocker ratio.

Any other ideas?

Stefan

[wrench459]

To say I have questions is a under statement on this subject.
After digging around I found this...
snip...This program solves the kinematic and dynamic equations for cam- follower systems. Radial, linear, and barrel cams with either translating or oscillating followers can be designed. Roller and flat-faced translating followers can be accommodated on radial cams and roller followers on barrel and linear cams. All of the standard, acceptable, double-dwell cam functions are included such as modified trapezoidal, modified sine, cycloidal, 345 polynomial, and many others. General polynomial functions and B-spline functions can also be designed using any user-specified set of boundary conditions to create custom cams that use multiple, single, or no dwells. External force-time loading functions can be applied to the follower. The pressure angles and radii of curvature are calculated for any user selected base or prime circle diameter.../snip

Don't you love answering one question only too have five more pop up!!