Today spoken with Wayne, and looked at an engine CAM with the following spec:
IVO: inlet valve opens 31 deg BTDC
EVC: exhaust valve closes 25 deg ATDC
IVC: inlet valve should close 59 deg ABDC
EVO: exhaust valve should open 65 deg BBDC
These valves have a duration of 270 deg, which is the same as mine. Its that the Lobe Separation Angle for my engine is 17 deg more.
So yes, this CAM is sort of similar to mine but with a bit smaller LSA.
We spoke about the next steps…..
What I am going to do is this:
- Move the CAM timing a little so that the IVO is slightly bigger then the EVC. So basically rotate the valve timing in yesterdays’s picture clockwise. But only a little. Probably one step in the timing gear in the back of the engine. This is close to perfect, without having to modifying anything. Currently the exhaust valve is fully open at 119 deg BTDC, and the mixture valve is fully open at 122 deg ATDC. So move that looking at yesterdays picture a bit clock wise, so taht the mixture closes a bit earlier.
- The second thing we are going to concentrate on is compression. If more compression can be gained, that will produce more power. This is a very low compression engine, basically on purpose as the fuels available at the time had a low octane content. Making the compression higher would make the engine ping. But with “better” fuels these days (higher octane), the compression can be increased, and will result in more power. We are going to try and find pistons that fit my engine and have a dome on top, a raised round top, protruding into the combustion chamber, giving us more compression and as a result creating more power.
- Also Wayne thinks the tappet clearance needs to be set to 20 for the mixture valve, and 25 for the exhaust valve.
These three steps are the last things possible we think without making modifications (that’s if swapping pistons is not seen as modifying) to increase the power output for my engine…..
So fingers crossed 🙂