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General Discussion / Re: Spark engine - making it last?
« on: June 14, 2008, 07:18:21 AM »
That's not retarded, that's advanced.
The best thing would be to set up your cam timing, intake, and exhaust runner length based on a set rpm. It is best to delay the opening of the intake valve and allow the engine to build a little vacuum in the cylinder so the charge carries more momentum coming in- Basically, open the valve at about 25-30ºATDC, and close about 5ºABDC. This combined with a proper length runner will create a sort of supercharging effect. You can easily tune an engine like this for 110-115% VE, as long as you're going for a fixed RPM.
I would start with an overhead valve V-twin of a lower HP rating (16-18) and keep the factory compression ratio.
If you do want a single side-valve engine, go for a Wisconsin or OLD Kohler, and bump the compression up to about 7.5-8:1. I think they both are about 6.5:1 originally. This will give you a much more user friendly power curve, and also greatly increase torque.
The best thing would be to set up your cam timing, intake, and exhaust runner length based on a set rpm. It is best to delay the opening of the intake valve and allow the engine to build a little vacuum in the cylinder so the charge carries more momentum coming in- Basically, open the valve at about 25-30ºATDC, and close about 5ºABDC. This combined with a proper length runner will create a sort of supercharging effect. You can easily tune an engine like this for 110-115% VE, as long as you're going for a fixed RPM.
I would start with an overhead valve V-twin of a lower HP rating (16-18) and keep the factory compression ratio.
If you do want a single side-valve engine, go for a Wisconsin or OLD Kohler, and bump the compression up to about 7.5-8:1. I think they both are about 6.5:1 originally. This will give you a much more user friendly power curve, and also greatly increase torque.