[DeTomaso] Cam selection - corrected

[Daniel C Jones]

Simulation of several cams for Dave Londry:

I used the flow numbers from the heads Dave McLain ported for Glen
Hartog (322 CFM @ 0.6).
Predicted numbers may be optimistic because they do not reflect the
area chage from small
2V intake to 4V head nor the the unusual collector of the Hall
headers.  Also the 351C
dyno mule results have been 10 to 15 HP or so optimistic, 30 ft-lbs
optimistic.  Assuming
the typical flat top TRW L2379F piston, 10.8:1 would mean the heads
and/or block was milled.
10.25 is more likely with unmilled block and heads.  I would want at
least 225 degrees intake
duration with 10.8:1 compression.  Note that the simulation gives a
better approximation when
simulating canted valve heads with 2 degrees tighter LSA.  That is a
cam with 110 LSA in the
simulation is really 108 degrees in the actual cam.  Using you Comp
Cams links, here are the
results:

275DEH as 110 LSA (closer to 108 LSA in canted valve head)
 447 5500 148 at 2000
 470 4000

275DEH as 112 LSA (mimics 110 LSA in canted valve head)
 436 6000
 466 4000

XE262H as 110 LSA
 429 6000
 466 4000

270H as 110 LSA
 431 5500
 474 4000

XE274H as 110 LSA
 468 6000  147 at 2000
 476 4500
 274/286 230/236 0.562/0.565 110 LSA

280H
 452 6000
 471 4500
 280/280 230/230 0.530/0.530 110 LSA 60 degrees seat overlap, (10 deg @ 0.050)

XE284H as 110 LSA
 486 HP @ 6000 RPM
 467 ft-lbs @ 4500 RPM
 284/296 240/246 0.584/0.588

The XE284H is a fair bit of cam for a 351C and has a 3.34 ramp rate
which is fairly aggressive
so may be a bit noisy.

I didn't run an optimization but I did pick a couple of lobes from the
Bullet catalog that I
thought might work well for you.   Bullet's custom flat tappets are
$172.50 versus $137.76 to
$146.58 for the catalog grinds from Comp's store.

Bullet custom
 277/285 228/235 0.581/0.541 110 LSA using lobes:
  HF277/335   277  228  142   .3350  .580 .000  CRA
  HF285/312   285  235  147   .3125  .541 .000  CRS
 473 HP @ 6000
 475 ft-lbs @ 4500

Similar in overlap to the XE274H but better power.  Running an
optimization on this should
improve upon this.

Dan Jones

On Sat, May 22, 2010 at 12:25 AM, Dave Londry <davel at emspace.com> wrote:
> Sorry - I had the rpm off by one column
>
> Dan has me in the queue for a run,
>  but in the meantime I've been running CompCams CamQuest simulator.
> I doubt that the absolute numbers are good, but it should be good for
> comparison.
> Using this for input
> ==========================================
> = 0.030 overbore & stock crank
> = 10.8:1  & 94 Octane
> = 4V-CC heads, ported, polished and matched, but no port-stuffers.
> = flat tappet & hydraulic lifters
> = Hall big bores & ANSAs which I intend to core out
> = Performer 2665 intake which I plan to replace with an AirGap
> = 800cfm Thunder (I also have a 600 Performer but the 800 seemed fine)
> = MSD 6AL
> ============================================
> The "best" choice was 275DEH
>                         Dur at 0.050  Dur.  Ramp    Lift
>        HP  RPM  FTP RPM   I   E   I   E  I  E  I     E     Spring#
>  275DEH 517 6500 468 4500 219 232 275 285 56 53 0.515 0.541   293
>
> It was attractive because of the slow ramp and low spring requirement
> Having a wiped lobe and short lifter kind of sensitizes you to those things.
>
> dave
>
>
> _______________________________________________
>
> Detomaso Forum Managed by POCA
>
> Archive Search Engine Now Available at http://www.realbig.com/detomaso/
>
> DeTomaso mailing list
> DeTomaso at list.realbig.com
> http://list.realbig.com/mailman/listinfo/detomaso
>