Quote:
Originally Posted by JoeMag
The cams are supposed to be set at 4.6mm at overlap. I was getting 4.2mm. An additional 3 degrees got them to 4.6mm.
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If I can be so bold as to say, the cams are never "supposed" to be at any setting. The only "supposed" I can think of, is piston clearance. Opening the valves earlier or later will have an effect on how much "work" the engine will produce and at what RPM.
3° will make a difference and that difference will become larger as the engine becomes more developed. I tell customers who don't get it, think of it in % terms. You let something slide and it amounts to a loss of 10 HP. Your engine makes 350 HP. A loss but not quite the effect 10 HP loss will have on a 160 HP engine. Don't give away the free HP you engine can make by thinking its not worth it. It is.
While you are at the timing checks, check the difference from the left side to the right side when setting the valve lifts at the height. You may, will probably see a crank degree difference there too. What you are now checking is the cam quality and the rocker arm quality. For the sake of doing it, check every lobe on both the Intake and exhaust side of the cam. Don't be shocked at what you see.
They may not be all equal. The idea here is to have the valves open all at the same crank degree and with the other losses known, try to obtain the same power output from every cylinder. Doing some math here can give you an idea of how much your engine could make if each cylinder produced the same power. They won't as this is the holy grail of engine building, trying to get even power from each cylinder. These air cooled engines are the worst, as thermal issues are high with the center cylinders siamesed and the air cooling somewhat hit and miss.