Originally Posted by northiam
Anyone had experiences with this cam? I like the figures!!
COMPU-PRO / PERFORMANCE LEVEL 5 - High torque, short oval
RPM Power Range: 3500 to 6500 / Redline: 7000 plus.
Part Number/Work Order Number 15380
Engine Application 351C-400M FORD
Grind Number 288FDP
ADVERTISED CAMSHAFT SPECIFICATIONS:
INTAKE: Duration: 288º Lift: 0.567
EXHAUST: Duration: 294º Lift: 0.58
RECOMMENDED VALVE SPRING INFORMATION:
Part # 68390-3 Single Dual X Triple
Approximate spring pressure: valve closed: 100/115 LBS.
valve open: 335/355 LBS.
INTAKE Opens: 26.0 BTDC 26
Closes: 48.0 ABDC 48
EXHAUST Opens: 58.0 BBDC 58
Closes: 20.0 ATDC 20
LOBE SEPERATION 105º
Duration at .050" Intake: 254 Exhaust: 258
LOBE LIFT Intake: 0.328 Exhaust: 0.335
Thanks for any comments
A camshaft is only as good as its intended purpose and the related combination of parts that make up the engine and vehicle. Here is an image that I made comparing this particular cam to a few others.
#1 is the camshaft you discuss here. #2 is a Crane F246 solid flat. #3 is the Crane F238 solid flat. #4 is the Lunati solid flat cam that I chose for my street/strip engine (that doesn't yet have a chassis). I'm not trying to compare my choice to this particular cam, rather it is intended to illustrate a point.
Torque is the green lines and Horsepower is the red lines. The base engine was taken from my own "Q-code" (the name that I've given it) engine specs. Basically, a 4-bolt Q-code block +.030", factory crank/rods, forged flat tops, 4V CC iron heads w/stainless valves, Torker single plenum inlet, 800 CFM DP and small tube headers with mufflers as the exhaust choice. Flow figures were as taken from my iron 4V heads that have no porting and only good bowl blending and hardened exhaust seats for unleaded petrol.
Note that in each case, the total lift figures were corrected for my 1.70:1 ratio rocker arms. Had I used a set of 1.73:1 rockers in the simulation, the lines would be only very modestly different. Since all are corrected for the different rocker arm ratio (than stock), then the data should be normalized for these purposes.
The "bigger" cams show much lower torque at lower RPM and extend the RPM range of this engine only slightly, from about 6500 on the low end to about 7000 on the higher end. The interesting thing to note is the peak torque and the time (over an RPM range) at peak. Numbers 3 and 4 have a very short period at peak before torque drops off significantly, while #2 and #1 have a relatively much broader RPM range at their peaks, however, in each case, the highest peak torque value is about 35-40 foot pounds higher in the more "peaky" torque cam, which is #4. Looking at the back side of the torque curve, one can easily see that all of the cams start to give it up at 6000 RPM as they seem to all intersect at that point. What that tells us is that our cylinder heads (as a function of flow) aren't helping us any beyond 6000 RPM, at least with these kinds of camshaft.
While the numbers do kind of make it a bit difficult to tell which line is which, I hope that most of you can make it out okay. I think that we can easily see that this particular combination won't rev it out to much beyond 7000-7500, quite likely due to the carburetion and the flat versus roller cams, but also because head flow isn't very good at those RPMs, either.
Another interesting point is that none of the cams makes a lot more HP peak than any of the others. Note how around 6000 RPM they all intersect again? Note also that the primary difference between #1 and #4 is that #1 carries its peak HP to about 6500 RPM while at that RPM, #4 is significantly falling off of the peak.
The principal differences between the two camshafts for this given engine combination is that #1 sacrifices lower end torque peak for broader mid-range torque available to the driver while extending the HP through a slightly longer and higher RPM range. #4 sacrifices top end performance for a much higher low RPM torque, but peaks quickly at reasonable "street/strip" RPMs for the combination.
We can surmise that the intended usage of the two cams is as their respective manufacturer's state. The Crower cam does in fact look like a good short oval cam where one would need a broader upper mid-RPM torque range to pull out of tight corners on a short track. The slightly extended HP range of the say, up to 7000 RPM of that cam would do well in the short straight aways, too.
The Lunati cam is billed as a good streetable camshaft for 9.5:1 compression on PULP...at least of the quality one obtains in the USA. The lower RPM grunt of this cam will do well with an automatic with a mild performance converter. It will also be "all in" by 6500 RPM, which makes it a reasonably good choice for stock/reconditioned factory parts.
Of perhaps the most interest is the comparison between #2 and #3. #2 leans more toward #1 while #3 leans more toward #4. They both represent good compromises between both ranges.
I wouldn't think that anyone using camshaft #1 or #2 would be very happy with it on the street without a lot more converter and rear gear ratio than a typical streeter's set up, while those with more gear and converter would probably prefer more cam than #3 and #4 offer.
The major difference between all of them (at least 3 of them) is the total peak torque. I'm sure that I've told forum members here before that I build for total torque, not for HP. #4 represents a very strong, peaky torque cam with #3 as its very nearly identical twin for any practical purposes (except cost!). #1 and #2 do extend the RPM range where power is being made to perhaps a maximum reasonable of 7000-7500 RPM.
The typical street machine won't need a "pulls hard on the top end" cam as much as a "pulls hard on the bottom end" cam...with the possible exception of overpowering the tires on the street at any RPM! A harder bottom puller will do better with "freeway flyer" rear gear ratio, which will save fuel costs while still performing well out of the hole.
But, it should be plain to see that no cam is ideal for multiple duties. Each cam is a compromise that is centrism for its intended usage.