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Camshaft Lobe Width? |
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Trader 
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881 |
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 Posted: Feb/28/2019 at 9:16pm |
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Yes, there are a few calculators that use 0.006" vs 0.009" on the lift point.
Anyhow, I was talking today with several cam manufacturers and my heads a spinning. Doing my own math for my 401 and bridge rockers: 273 duration intake and exhaust, KISS. 111 LSA, 107 ILC Intake open 29 BTDC, close 63 ABDC Exhaust open 71 BBDC, close 21 ATDC 224 @0.050 0.485" to 0.493" lift Have not looked for this cam yet but the math put 7.9:1 DCR with everything else and 83% of usable power stroke which turns out to be quite good. This in turn math wise looks like 460 HP @ 4500 RPM but I believe the math is being way too optimistic. Different formulas, VE, heat loss,valve size, put this at 412 ftlbs torque - fairly flat on the power band and 420 HP at 4700 RPM. Need to go back to math class!!! Head hurts - good night,
Edited by Trader - Feb/28/2019 at 10:03pm |
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Shawn_Watson
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Joined: Dec/05/2018 Location: Carlsbad, NM Status: Offline Points: 117 |
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Posted: Mar/01/2019 at 7:42am |
What are you using for this? Shawn
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Trader
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Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881 |
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Posted: Mar/01/2019 at 8:33am |
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This is a combination of several tools:
1) a calculation in crank torque moments by degrees based on input of stroke, bore, rod length. This is based on 100% efficiency but does give the highest torque angle as a start point. 2) based on this angle, using Greyhounds posted information on cam aggressiveness for bridge rockers, calculate the duration required. Also using his insight to calculate the best point to open the exhaust valve - thanks Greyhound. 3) based on the duration and the aggressiveness come up with the @0.050" 4) Calculate the dynamic torque with an online calculator and tweek for near 8.0:1 DCR 5) Plug everything back into the crank torque to get kw pressure. 6) Plug that into an engine HP conversion and get some numbers that you would never know true unless you put it on a dyno after the build. Easy!!! After all this I got thinking yet again and changing my exhaust duration to 268 and 221@0.050 to reduce overlap and move the opening to 19 ATDC, close 69 BBDC, Lift reduction to 0.476" ups the DCR just a hair but delivers 5 HP more (says 8 HP but I still don't believe it). Any less duration seems counter productive unless I change the LSA which in turn reduces overall HP for street application RPM's. Any more duration seems counter productive as it opens the exhaust early and you loose HP also.
Edited by Trader - Mar/01/2019 at 9:19am |
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Shawn_Watson
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Joined: Dec/05/2018 Location: Carlsbad, NM Status: Offline Points: 117 |
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Posted: Mar/01/2019 at 11:05am |
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Interesting. If I were doing a 9.5:1 401 with stock heads and exhaust manifolds, I'd probably default to Howard's .903 lobes for something like 271/271 at .006, 224/224 at .050 on a 107 +5 without looking at calculators. The lift ends up being .552 so that probably wouldn't work without changing the rockers, though.
I wonder if running numbers like you are would make me see something worth changing. I'm pretty sure it wouldn't be considered a "sleeper" cam
 Edited by Shawn_Watson - Mar/01/2019 at 11:07am |
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Trader
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Posted: Mar/01/2019 at 4:22pm |
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Actually priced the custom grind today and as it would not come as part of a cam/lifter kit it's $140 more. A little much so started looking at off the shelf with new found knowledge and the Lunati 10100276 would be very close with the ICL at 104.
More lift does not necessarily make more power. Timing events make the power. Decision time I guess. Thanks for everyone's input.
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Trader wrote: