another cam question (is the worth it)

[Zorm]

Picked this up today at the Summit scratch and dent bin http://www.summitracing.com/parts/CCA-K68-235-4/ (didn't pay that much for it though) I am asking if this cam setup would be worth putting im my engine. What I have is 4.0 HO head on a 258, ran it for the past 5 years. Now I am putting on a 2000 intake along with fuel injection and a 62mm throttle body.

Any cam guys out there know what I can expect from this cam in set up?

thanks

[Dhaos]

The stock cam has about 263/263 duration 110.5 split -7 degrees. .396 lift. This one has a shorter overall duration but a higher .050 duration(more aggressive lobe) and a higher lift. The split is about the same and it will be much more advanced as comp loves +4 in all their cams vs the -7 in the stock lobe.

Short answer, you can expect no real change at 5k but everything below that will improve without costing you vacuum or idle torque.

[IH 392]

My dyno simulations with this cam show that it pretty much SUCKS below about 4000rpm!?, it's only fair right up against the rev limiter.

[Dhaos]

Which software did you use? I'm not seeing these results, operator error on my part?

[IH 392]

DYNO 2000, version 3.08
The Comp 235 cam shows 10 less HP and 30 less tq at 2000 rpm's, they don't equal out until 4000 rpm and by the time the rev limiter kicks in the comp 235 does show a 20hp and tq advantage, don't know how you drive but I rarely keep it between 4000 and 5000 rpm's!

[Dhaos]

Are you calculating values at .050? I use dynomation and enginesim, and neither came close to losing torque at all rpms below 4k compared to a stock 4.2 cam. Even if duration is higher, the more aggressive lobe and 11 degrees difference in centerlines would offset a larger difference in duration at the lower rpms. I would say the 231-4 cam would be better as a towing cam, but the 235 is still better than the stock cam except right at idle. The 258 cam has a larger seat to seat duration, lower lift, less aggressive lobe, and is 11 degrees more retarded; I don't see how the comp cam loses torque compared to the stock profile.


I attached a document with the stock 258 camshaft specs for comparison.

[Dhaos]

Attached here is my results with dynomation. Again, I'm not sure what dyno2k does, but this is what I saw with the lighter lines being the comp cam and the darker being the stock profile.

[IH 392]

I never even wasted my time running a simulation with a 258 cam, they aren't much good for anything but tent stakes, I compared it to the OBD II cam +4*

[SilverXJ]

Are you calculating values at .050? I use dynomation and enginesim, and neither came close to losing torque at all rpms below 4k compared to a stock 4.2 cam. Even if duration is higher, the more aggressive lobe and 11 degrees difference in centerlines would offset a larger difference in duration at the lower rpms. I would say the 231-4 cam would be better as a towing cam, but the 235 is still better than the stock cam except right at idle. The 258 cam has a larger seat to seat duration, lower lift, less aggressive lobe, and is 11 degrees more retarded; I don't see how the comp cam loses torque compared to the stock profile.

I used Desktop Dyno 2003 with a 258 block, 4.0L head and a 87-95 Jeep cam compared to the 235 cam. The 235 was better pretty much all around. Like your findings.

BTW, the springs, retainers and locks in that kit will not work on the 4.0L head.

[I6FAN]

How does the 235 stack against the 231 & 239? I noticed the 235 is not listed in the compression ratio calculator; I guess it's not a popular choice???

[Dhaos]

I attached 2 sims I did with 231-239 cams one using the above information and another with a common stroker build. Both are assuming perfect timing and a 12.5:1 fuel ratio(and other things, these numbers will be inflated and are guides only).

It seems that the 239 cam is for someone building a stroker for an amc car that's light and plans on seeing the higher rpms a bit. The big restriction is the header selection, heads, and intake. This being said, I recommend the 235/231 cam. These 2 are so close to each other that that I had to read the BMEP pressures to really see much of a difference.

On that note, the 239 did have more reversion at 1k which became more obvious when the run was simulated using more cycles.

The chart shows a lot more horsepower, but I don't read many people here really revving them out or running loose converters.

I didn't think to run a 4.0 cam, I was under the assumption he was using the cam that came in his block which now we can understand why we got such different results.

[I6FAN]

Agreed, thanks for posting!

[Zorm]

wow, this is good, would this be cam be worth putting in a basic stroker, 4.0 nothing major and the 258 crank/piston rods. No boring of the engine, just stock pistons,

any thoughts?