On the top end - it seems like smaller cams seem to react better than bigger cams to the same adjustment. This kind of makes sense to me, cause if you already have big overlap - one degree more isn't going to give you that much. Here's an example. Retarding the exhaust 4 degrees on the Crane 12 shows a nice torque gain on the lower end up to 3500, and a 5hp gain from 6500 up. The same adjustment on the Crane 16 shows a real nice torque gain down low, but there's only a 2hp gain on top.

In general - Retarding the exhaust always shows an improvement on the top end - and usually shows a neglagable decrease in power in the mid range. Sometimes retarding the exhaust shows a gain over the whole range. Advancind the exhaust always removes power from the entire range. Retarding the intake shows an increase in top end and a decrease in low/mid range(usually substantial compared to the gain in the top end). Advancing the intake usually shows an increase(sometimes neglegable) in the mid range and a loss(sometimes substantial) on the top end. Mixing and matching advance on the intake and retard on the exhaust usually shows a curve that is influenced by doing each adjustment on it's own.

I don't know what the theoretical answer is, but according to what I'm seeing on this program it seems that in general - retarding the exhaust seems the best way to make power overall. All cams are different though, and "whats looks good" in the low, mid, and high range may be different for some people. Most of the time I can get a descent curve by just retarding the exhaust. Somtimes it takes a mix of retarding the exhaust and mucking with the intake to find what I want.

One thing I will say about Dyno2000 - they could have made it easier to make adjustments for DOHC. They have this Timing adv/ret field - that you can easily adjust both by - like for a single cam engine. But if you want to tweak the timing seperately then you basically have to change the profile through the cam math window. It works and you get used to it, but it could be made easier.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html