Chewy wrote:Just things I have heard..
SP gives better bottem end torque, DP gives better top end HP
I agree with this. I had two almost identical donks. Both 1640s. Extractors, 009 and a 30pict. One was SP ands the other DP. The SP pulled off the lights heaps better, but the DP would rev out to 5k, if pressed.
Of interest, Class 5/1600 in the US offroad scene has to use SP motors and they get 80 plus HP out of them with mostly stock parts. And they thrash them. That is with a slightly offset ground crank for exactly 1600cc, but even still, with a single carb they go hard. Not sure of the cam they use but it's not standard either. Look up some specs on one on the net somewhere. I try and find some specs in a mag if I can.
Do a search on 'Adam Wik' racing engines, you should find something. He's the top 5/1600 guy I think.
Oh the other thing to remember is this. A single carb motor self regulates. So you can hold your foot flat and it shouldn't over rev valve bounce. The carb chokes it enough to rev limit it. This is what helps VW motors last even when thrashed.
[Edited on 2/6/2005 by pete wood]