- Joined
- Nov 26, 2009
- Messages
- 3,081
Yves - I gave Web cam a sample cam with perfect timing and whenever they grind cams for me they use the intake lobe centerline for reference. They call this sample cam a "line up cam". Before I worked this out with them the cams were not always the same. So I'm glad it worked out for you and that you confirmed that the cam is correctly timed. There can also be cam timing errors from motor to motor because of various timing gears and keyway locations in the crank, keyway slots in the gears/sprockets etc - so its still best to check.
Ken and Worntorn - your various cam timing methods are excellent but different ways of verifying cam timing. I also use the same methods as per Axtell's instructions ( as Ken) and notice that the intake is always advanced a couple/few degrees (as Worntorn). But when you measure the valve lift at TDC the intake lift is always higher than the exhause at TDC with symmetrical cams and its just easier to measure (and record) that lift than to do the degree calculations. The lift specs I provide at TDC are what you see when the cam is degreed correctly - the intake has X amount more lift than the exhaust. Some customers are not familiar with the degree calculations but they can usually check that there is more lift on the intake at TDC - even if you just peek through the ports. Generally if the timing is wrong it is too retarded. So if the intake has less lift than the exhaust - you have to do something about it. If you're going to be lazy then you can tolerate the in/ex lift being equal at TDC and still have a good running motor. But they run best a little advanced.
Ken and Worntorn - your various cam timing methods are excellent but different ways of verifying cam timing. I also use the same methods as per Axtell's instructions ( as Ken) and notice that the intake is always advanced a couple/few degrees (as Worntorn). But when you measure the valve lift at TDC the intake lift is always higher than the exhause at TDC with symmetrical cams and its just easier to measure (and record) that lift than to do the degree calculations. The lift specs I provide at TDC are what you see when the cam is degreed correctly - the intake has X amount more lift than the exhaust. Some customers are not familiar with the degree calculations but they can usually check that there is more lift on the intake at TDC - even if you just peek through the ports. Generally if the timing is wrong it is too retarded. So if the intake has less lift than the exhaust - you have to do something about it. If you're going to be lazy then you can tolerate the in/ex lift being equal at TDC and still have a good running motor. But they run best a little advanced.
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