Originally Posted by mtx3ron
Thanks guys for all your advice I already run a novarossi and it is a great engine ,holds a tune and very reliable my concern is it is a offroad .21 buggy engine p5 . Not sure how competetive this engine will be racing onroad .
P5 is a great buggy engine, lots of torque with good top-end (by buggy standards). On short tracks, there would be no down-side. I have run buggy engines in 1/8 on-road before (being a tight-wad, trying to save a buck). On one car, I could not get the two-speed adjusted. The RPM was to low for the available adjustment. Heavier springs were required. In general, a buggy engine will give less RPM, more torque(actually less torque, but it occurs at much lower RPM so it feels like more), and more fuel economy.
The on-road .21s have more advance for exhaust timeing (higher port/opens sooner) and more advanced induction port timing. The on-road engine will produce more peak torque/HP/RPM and fuel consumption.
If you run larger pinions and make apropriate adjustments to your centax and 2 spd, you should be OK. Even with the taller gearing, you may not have long enough legs for the bigger tracks.