Advance/Retard cam timing and Dyno 2003 sims

[Retlaw01XJ]

I've been using Dyno 2003 simulation software to do some cam comparisons.
The optimum cam timing for most cams is with the cam retarded 4 to 8 degrees, for an intake centerline between 113 and 114 degrees.
...stock (late) cam, Crower 44243, Comp 231 and 232.....
Running cam at the recommended 108 -109 intake centerline kills the peak power 4000-4500 rpm with no real gain in the low-end.
Anyone else getting the same results?

[Cheromaniac]

I've been using Dyno 2003 simulation software to do some cam comparisons.
The optimum cam timing for most cams is with the cam retarded 4 to 8 degrees, for an intake centerline between 113 and 114 degrees.

Running cam at the recommended 108 -109 intake centerline kills the peak power 4000-4500 rpm with no real gain in the low-end.

There are too many variables involved to draw those conclusions.

[SilverXJ]

Not only that but most cams already have 4* advance ground in them, so maybe it holds true for that case. However, it isn't so for other cams.

[Retlaw01XJ]

No, I'm saying the cams run better retarded in the Dyno 2003 simulations, I don't mean the real world!
Any one else with that software getting similar results?

[Cheromaniac]

I've found that for most of the aftermarket cams in a 4.6 stroker, the best spread of torque from idle-5200rpm comes with about 4 degrees of advance.

[IH 392]

My simulations with Dyno 2000 even shows the OE '97-'00 benefits from 4 deg advance, retarding the cam reduces power and puts the power band right around the rev limiter.

[Retlaw01XJ]

I must have something wrong in my setup, but I can't find the error.
I'm using the Mopar 225 slant six for the base block and using the Alex22 head flow data for the 0331 head.
Using different induction and exhaust systems still gives the retarded cam the best power.
I have Dyno 200 as well. I'll try that version and start from scratch to see if I get similar results.

[shawnxj]

instead of using the slant six why not just use the 4.0 and give it the correct stroke

[IH 392]

The Crapsler 225 has a holy crap long stroke and pistons about the size of pop cans!, that probably has a lot to do with your funky results?

[Retlaw01XJ]

instead of using the slant six why not just use the 4.0 and give it the correct stroke

The software didn't include any AMC engine files.... or even any straight six files other than the slant 225.
I wonder if the sims even take into consideration unique characteristics of engines other than bore, stroke, and head flow?

[shawnxj]

it's in there you just have to look. i know this because it's in mine

try looking in the jeep files. i haven't looked at mine in over a year but i know it's in there

[NorCalChris]

I don't have the program anymore, but mine definetly had the AMC 4.2 in it.

[Antifreeze2]

I had similar results of low end gains with a comp 231 cam retarded 4*. The only pre set thing I used was dual plane intake manifold. Inputed the rest of the variables.
My question is how does the Comp 231 cam advance 4 degrees? These charts show the actual valve opening as presented on the cam sheet, which my calculations put me at 8.24 DCR, but the website calculator gave it to me with 4 degrees advance. Would kicking it back 4* put it at 0 or -4? Also a silly question, but does the cloyes set change 4 or 8 degrees since it is on the crank gear?

4 retard


0 advance/retard


4 advance

[Antifreeze2]

I think I figured it out, comparing intake valve closing angles. I is smart - SMRT

[SilverXJ]

We don't have a dual plane intake manifold. The 4.0L manifold is more like the TPI.