Thread: Cam Help Please

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Tango, Thanks a lot for your assistance. I have bookmarked your site.

Don Shillady
Retired SCientist/teen rodder

Don, it has been my experience on the DynoSim that there is little difference between the power/torque made with 1.6 over 1.5 rockers. You can generally find more of a difference by advancing or retarding the camshaft than you can with different rockers. Anyway, here are the figures with everything the same as the last DynoSim except using 1.5 rockers.
RPM HP TQ
1000 49 259
1500 93 327
2000 134 352
2500 171 360
3000 223 391
3500 270 405
4000 305 401
4500 331 389
5000 336 366
5500 327 313

Here is the sim with 1.6 rockers for comparison....
RPM HP TQ
1000 49 259
1500 93 327
2000 134 352
2500 172 361
3000 224 392
3500 271 406
4000 307 403
4500 336 392
5000 340 370
5500 332 317

With that Camshaft them #s are on the High Side . It will Fall off at the RPM's you listed . Yes the 1.60 Rocker can Make up to 20 More H.P on that builds . Also them EPA Blocked intake ports are a H.P Killer . Your right at 300 H.P . The 1969-70 350 300 HP Chevy Engine had a Camshaft that was just a bit Smaller 390" / 410" But had 10.25.1 C/R and better Flowing 1.94" / 1.50" Heads with a 750 Q-Jet Non EGR Intake 300 H.P at 4800 RPM's with 380 Lbs at 3200 RPM's .

Thanks Tango and Tech1! It would seem I have a rebuilt SBC 350 which I will think of as a 300 HP/ 400 ftlb motor. I think that is what is needed for touring on Interstates at 65+ mph with an aerodynamic brick of a Model A with fenders. I am concerned about the pushrod holes and at present I do not plan to remove the heads for further work, although that is possible in the future. As soon as we have a reasonably warm day I will probably install the 1.5 roller-tipped rockers and take what I can get. It is obvious to me that a rod is never really "done" and future modifications could occur without changing the cam such as Vortec iron or Corvette aluminum heads but for now I think it is best to get it running. There was a long delay due to not knowing what cam I really have but you guys have cleared it up pretty well, Thanks!

Don Shillady
Retired Scientist/teen rodder

Tech1, I am working on a poster to give details if I attend any local shows this summer with my '29 roadster and I want to use your Dynosim results for my engine. In going back over this old thread I wonder about the 5000 rpm HP. Using the formula: HP=(ft. lb. torque/5252)x(rpm) your HP and torque values check at 3500 rpm but I don't understand the Dynosim results at other rpm. Can you check that old Dynosim chart so I can put your name after the data on my poster?

Well further checking shows using your numbers that at 5000 rpm I get

(366/336)x(5000)=5446 instead of 5252 so I guess that is within the uncertainty of the simulation.

So 336 HP is reasonable and on the low side at 5000 rpm but if I use the 5252 constant I get

(366x5000)/5252 = 348 HP. I have looked at the Comp Cam dyno charts and calculated the constant and they showed the same 5252 +/- 200 so I guess you need very precise dyno values but the theoretical value of 5252 does show up in the crossing points in the Comp Cam dyno charts. At 5500 rpm we should be past the 5252 crossing point and here I get

(317/327)x(5500)=5332

Apparently the Dynosim program arrives at the HP and Torque values seperatley. If I were writing the program, as I did write programs for many years, I would have just calculated one or the other of the HP or Torque values and used the 5252 constant to get the other value. As far as I know in a real dyno Torque is measured and then the formula is used to calculate HP using the 5252 constant so the experimental dyno chart should come up with the 5252 constant but the simulation apparently uses internal formulas for HP and Torque individually.

Don Shillady
Retired Scientist/teen rodder