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Author Topic:   How would this cam work?
dode
Dirt Freak

Total posts: 417
posted July 09, 2002 12:07 PM UIN: 13209501
Ok...here are the specs for our motor:

.060 over 350
stock crank and rods
stock cast iron intake
Q-Jet
log manifolds
9:1 flat tops
993 heads

Ok...this is a 3400 lb. car on a 1/2 mile track running 5.29 gears. I found this cam:

Renegade Racing

cam lift .298 intake/.298 exhaust
lobe center 109 intake/109 exhaust
adv duration 291 intake/291 exhaust
.050 duration 222 intake/222 exhaust
timing: BTDC 0 ABDC 41 BBDC 48 ATDC -6

from using Engine Analyzer 3.0, this seems to be a good cam for our combo. We don't run a high rpm (5300 - 5400 max so far according to the tach, might be a little higher though). With this combo, it shows a nice torque curve of 325+ ft lbs from 3000 - 4500 rpm, with a peak of about 335 at 3600. It also shows 300+ ft lbs from about 2500 rpms to about 4900. This is more torque than our old cam gave us I am 99% sure, as we seemed to have some problems starting the race and coming out of the corners. For the hp curve, it makes a peak of 280 @ 5000 rpm, and has a pretty decent curve. Does this sound like a good cam, or should we look to something else? Plus, I like this one because I can get it cheap. The other ones I was looking at were Speed-Pro cams from Midwest Motorsports (we have one here too), but I can't find any of the timing specs on them so I can run them through the computer. It just gives lift and lobe centers and duration. Can I calculate the valve timing from those numbers? Thanks.

John



racer17j
Dirt Forum Champ
Total posts: 1565
posted July 09, 2002 11:47 PM UIN: 54865418
our last years point champ ran one of those speed pro cams and he was a rocket won 17 races between the two tracks champ at one 2nd at the other if you call midwest i'm sure they can give you the specs for the timing of it just tell them you bought a cam from um and it didn't have a card in it if not i have one laying around somewhere i was gonna try i'll see if it's the same one. do you have the .510lift on bolth or the .510int.533exh?

BayouGent
Dirt Forum Racer

Total posts: 87
posted July 10, 2002 01:27 AM
John do you run under a lift or vacuum rule?

dode
Dirt Freak

Total posts: 417
posted July 10, 2002 10:06 AM UIN: 13209501
I am working on getting the speed-pro specs. Midwest told me they are good cams. No, we have no lift or vaccuum rule, and we run on a half mile track. Our valve springs are good for .550" of lift. Thanks.

John

dode
Dirt Freak

Total posts: 417
posted July 11, 2002 02:57 PM UIN: 13209501
Ok...here is the cam I have picked out. After playing around with Desktop Dyno and Engine Analyzer, it seems that this speedpro cam is the winner: CS1146R from Midwest Motorsports.

Int Dur @ .050 244
Exh Dur @ .050 254
Int lift .510
Exh Dur .533
Lobe Sep 112
Timing:
btdc 15
abdc 49
bbdc 64
atdc 10

using all the specs in Engine Analyzer 3.0, here are the results:

RPM HP TQ
2000 55 145
2500 98 206
3000 142 248
3500 198 297
4000 249 327
4500 285 333
5000 305 320
5500 308 294
6000 278 243
6500 230 186

The data from desktop dyno is slightly lower, but the curve is very similar, except DD showed peak hp a little higher. Both showed nice smooth torque curves, which is what I am looking for. Peak power doesn't do you much good, other than bragging. Those seem like pretty good numbers don't they? What do you guys think? These are really about the best looking numbers I could get from either program without going with some crazy custom cam or anything. I know these results aren't exact, but I think my models are very accurate, so they should at least show good trends. Thanks.

John


Tim Weiss
Dirt Roller

Total posts: 12
posted July 11, 2002 03:20 PM
how about the mwms5 cam dur@ .050 249 LIFT 508 106 lobe sep. adv.dur 290 this is a solid cam

dode
Dirt Freak

Total posts: 417
posted July 11, 2002 03:21 PM UIN: 13209501
Sorry...hydraulic cams only, and they actually checked last week from what I heard...

John

BayouGent
Dirt Forum Racer

Total posts: 87
posted July 12, 2002 01:03 AM
John if you could find a way to get your compression up just a little more you'd like the results of that cam better. 9:1 is a low compression ratio for a cam with that much duration (244/254) at .050. Using flat top pistons and possibly having those heads milled down a little would bump it up a little. Just a thought.

dode
Dirt Freak

Total posts: 417
posted July 12, 2002 08:12 AM UIN: 13209501
We run in a 9:1 class, so we can't go up anymore. Do you think we should look elsewhere for a cam, even though the numbers seem to come out really nicely in the simulation (yes, I realize it is only a simulation). I realize we aren't going to go out and win races this year. We don't have the motor, but we need to get our driver some good competitive seat time. Thanks.

John

Monster
Dirt Maniac

Total posts: 135
posted July 12, 2002 05:37 PM
I have (and do) use EA Pro with good results, so with that said, look again at your figures. Determine a RANGE of rpm that you use(you may have to physically threaten the driver for this), then go for the area under the curve, that is, average all of the torque and hp figures in your range if the sim will not do it for you. Change your specs, then watch what the AVERAGE does. This will show you why you don't need near as much cam as you think. Most guys brag about how BIG their cams are. I love to mention how SMALL ours are, especially after we've just spanked 'em!

dode
Dirt Freak

Total posts: 417
posted July 12, 2002 05:46 PM UIN: 13209501
That makes me feel much better....that is almost exactly what I did. Being an engineer, you learn the value of "area under the curve" very early on. I too would much rather run a smaller cam. There is no need making more power when you don't need it. All that does is produces more heat. Plus, bigger cams are harder on valve trains, generally speaking. Thanks for the advice!!

John

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