Miles, you are probably in the neighborhood on your horsepower guess. But with stock valve springs you're not hitting 6000 rpm. I have a setup somewhat similar to yours. Manco Intruder 2 seat kart. Big kart, 68" wheelbase but not heavy. Same engine, 301, same cam ( I love it ) 50lb springs head has been milled .050" and ported by a professional head shop, header pipe, low restriction air filter, but I am running a re-jetted ( main and pilot ) stock style carburetor. 18" rear tires, 6 to 1 gear ratio. With 2 people ( 400 lbs ) it will go 48-49 mph. I'm guessing with just myself it might tickle 52mph. If you haven't already, put the light weight rollers and the stiffer springs in your 40. OMB sells them. I could hardly believe the difference it made. Not only in the hole shot, but I picked up at least 4 mph on the top end. I know that the billet parts for this engine ( rod and flywheel ) are quite expensive, I think I paid about $330 for the two, but get that f - - cking pos stock flywheel off there before it comes apart and tears up your engine and maybe your back or right arm. The rod might be OK, plus it won't hurt YOU if it lets go. But stock flywheel, performance cam, and governor delete, you're playing with fire.
