Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

In the true spirit of the Toolman, I am always looking for a way to increase my snow blower horsepower. I came across a company that sells karting engines & supplies. They claim that if I send them my HM100, they can add their hop-up kit and increase the horsepower by 3 to 5 HP, without affecting reliability. I was clear that I'll be using it on a blower not a kart, but I haven't been able to find out exactly what it is they do to the engine. Cost is $135 + shipping one way.
Does this sound reasonable or too good to be true?

Cheers

It may make 3-5 more HP, but you need to be sure it makes that additional 3-5HP in the RPM range you'll be using. 3400-3700 RPM. It doesn't do you any good to move the torque curve up the RPM curve to make more top end HP if you actually LOSE torque in the lower RPMs where you need it most. What you want to accomplish is to increase torque in the 3000-3700 RPM range. That can be done pretty easily by increasing compression. You should use high octane gas after that. Detonation can do AWEFUL things. Cracked rings, hot spots, "hole-ing" the piston.
A cam is a really tricky thing. You need to consider what else you're doing when selecting a cam. Any "performance" cam you choose will undoubtedly have higher lift, but to accomplish MUCH higher lift without roller lifters, you end up increasing your duration and overlap if you keep separation angle constant. That leads to less low RPM torque. You want a cam with its torque peak in the 3400-3600 range. Unless you plan on running your engine at a higher RPM. But that requires other components be upgraded as well.

2 things which will definitely make more torque with the same cam...
Higher compression - I'm sure you can find a high compression head.
Porting - Smoothing (NOT re-profiling), matching carb port to intake port, 3 or 5 angle valve grind.

You can also experiment with...
A larger muffler (not too large, or you lose low end torque)
A carb to engine spacer. You can tune the resonant frequency of the air column going into the engine in a narrow RPM range to increase volumetric efficiency. You should be able to Google it to find an online calculator or something. Remember the Chevy TPI intakes? Their runners were about 16" long and make great low end torque. Long runners=low end, short runners = top end.

And for God's sake, get an adjustable main jet on your carb.

I specifically told him that the motor would be on a snowblower that would be running up to 60 minutes at a time & I wanted to maintain the reliability and keep the hp increase in the 3100 to 3500 range where I'll be using the machine. With respect to a high compression head, I was thinking of bringing mine to a shop to get a little shaved off & accomplish the same thing. I'll have to research & find out what kind of clearance there  is valve to piston. I've done the polishing & port matching on a car engine but I was wondering how much of an effect it would have here since the passages are relatively short. There already is a sort of intake manifold on the HM100, but I suspect it's more to put the carb in a more convenient location for the shroud to keep things warm. I wonder if a straighter longer manifold would help low end torque as you said (but then I'd have to play with governor & throttle linkages)?

Anyways, thanks for the info & I will start poking around the karting forums to see what I can learn.

Cheers

Yeah. Let us know how it goes. Very interesting stuff.

Clearance of valve to  head------.... You can take it apart and put modeling clay over the valve on the head , bolt it back together and then after pulling through the rope slow a few times, take it apart and mic the Clay's clearance...( to see how much you can shave....

Or you could have the head filled in over the piston a bit...

Friiy