Jerry I notice that on dynos listed from your shop on the LT500 most of them start making power at 5000 rpm is this part of your pipe design? or do you just start the graph in the upper rpm?

I do not consider power below 5000 RPM that important.  The power valve will add 5 to 10 hp at 5000 RPM with my pipes but I do not consider power in that range important.  If you are at 5000 RPM and need more power, down shift one gear and it will put you in the 6000 to 6500 RPM range where you will have 65 to 70 HP.

A properly functioning power valve will make a good-looking dyno curve but I do not believe it is worth the risk of burning a piston if it closes too late when you are running the engine hard.  This happens frequently when the valve malfunctions or is not adjusted correctly.


Example:  Using one of the graphs posted in this thread.

RPM    No Power valve    Functioning Power Valve
4500   28                      33
5000   35                      45
5500  48                      51
6000   65                      65
6500   70                      70

If you are rolling along at 4500 RPM and some one pulls up along side of you and gives you the nod.  Are you going to leave it in the current gear and open the throttle and have 33 HP or down shift and have 65 plus HP.

If you spend most of your time in the 4500 to 5000 RPM range why spend thousands of dollars on porting, carbs, and pipes etc..   None of these modifications improve the power significantly in the lower RPM range where you are not “on the pipe”

If you are racing someone your RPM will not drop below 6000 RPM.  With my engines and pipes and the power valve adjusted properly, the power valve effect is over by 5500 to 5800 RPM.