How Cam Timing Effects Power Harley Tuner & High Performance Discuss How Cam Timing Effects Power in the Harley Tech & Harley How-to forums; I was testing the effects of valve timing the other day and thought that I would share the results. This is the same bike and all of the cam timing ...

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I was testing the effects of valve timing the other day and thought that I would share the results. This is the same bike and all of the cam timing and dyno runs were performed within two hours. The engine components doesn't matter. The only thing that was changed between dyno runs was the cam timing. The engine was originally at "0"degrees. I didn't tune the AFR on these runs so, if the AFR was tuned, the numbers would be higher. The purpose of the article is to show how that different cam timings can improve HP/TQ flow and lines. Remember that changing the closing of exhaust valve timing, changes the wave timing in the exhaust.
You can change the exhaust waves by changing the exhaust length and diameter and/or by changing the exhaust valve timing.

This first graph is negative eight degrees.


This graph has the cam timing advanced ten degrees.



This graph has the cam timing advance five degrees.



I tried a lot of different cam timings and post these three.

Conclusion: The +5 degree timing had the most power increase for the cam and exhaust combination that was used. It gained 10+ TQ / 7+ HP just by changing the timing from the original "0" timing . It will gain a few more when the AFR is corrected.
This proves the exhaust wave timing theory.

Things to look at on each graph is where the TQ is at 2500 - 3000 RPM, where the peak TQ occurs and the flow of the lines.