blue missile said

Tracy,
thanks for the reply. I have noticed that some people seem to think that a discussion of substitive information is called thread killing. Since I am new to all of this I don't understand that.

Your'e correct about the Hp & Tq numbers Rathar than using the words above and below I used the symbols < & > greater than, less than, a force of habit, my apologies.
As th Hp increases above the apex of the curve usually the Tq decreases before the apex. A normal trade off in design.

Here are the specs on the two cams:

XE285HL;part# 20-228-4, RPM range 2500-6500, valve timing .006, lobe center 110, intake centerline 106, adv duration 285/297, dur @.05=241/247, valve lift @1.5:1= .545"/.545", lift @ 1.6:1= .581"/.581" (what I'm using)
IVO=37, IVC=69, EVO=83, EVC=35

XE295HL; part#20-229-4, rpm range3000-6800, valve timing .006, lobe center 110, intake centerline 106, adv duration 295/307, duration @ .05 251/257, valve lift @ 1.5:1=.564"/.564", @ 1.6:1=.601"/.601", IVO=42, IVC=74, EVO=88, EVC=40

I will tell you, that so far only the most agressive roller cams can match the numbers for these two grinds. I do not want to go that route when flat tappets will produce these kinds of results.
I included the timing events so you can also look at the DCR and Cranking pressures created.
It was the DCR created by the 295 that has me selecting the 285. More in line with the design goals.

The only thing that really causes the numbers to go off the chart is the numbers for the new Brodex head for the SB LA motor.Thay went up into the mid 600s with no other changes.Right now they are simply not in the budget.

Hope this helps, let me know
Andrew

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moper said

Fishy, the old school 284 is not a fast rate cam by todays standards, just bigger duration at mid lifts than what was avaialabel in the early 70s.

Right. I didn't mean I thought it was a real fast rate cam. Just meant it does have a faster rate than the standard XE series by Comp cams. Sorry if it came out wrong.

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I know you guys place a lot of faith in Desktop Dyno. I can tell you it is good at plotting trends, but not specific numbers. It is only a trend. The margin of error is more than the differences you are noting in the results. The reason it is like that is it averages a lot of things for the ease of the calcuations. The original version (which I played with a lot back in the mid 90s :) ) didnt have flow numbers, it had "stock, ported, and race ported" for heads...lol. I know it's gotten a lot better, but in terms of cam lobes, it is woefully lacking. That is why the roller profiles pull similar numbers, and even the hydraulic lifter calculations are iffy.

Gotcha. Have you used the newest version? Just wondering since I have the latest version and it supposedly has a much improved cam program. Or so they say. I never saw the original version so I don't know what it was like. I do know in the cam portion of the program it plots lift and duration throught the 360 degree cycle. Do you think it's still lacking due to rounding off?

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I do not want to be known as a thread killer, so if this was aimed at me, I apologize. It seemed to me there were two identical (or very close) threads posted simultaneously, and it's easier to stay focussed on one.

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Same here. Sorry to get off track of the original post.

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