After installing Derek's pulley system I'm degreeing the cams. My question revolves around a chart in an earlier post. Image Unavailable, Please Login This chart shows and exhaust lobe center of 72 degrees. Can someone explain this to me as I get 108 degrees using a cam calculator. Image Unavailable, Please Login What aren't I seeing. Barry
The math in the calculator appears to be: 180 (BDC to TDC) + 50 (open before BDC) + 14 (open after TDC) = 244 . 244 / 2 (midpoint) = 122. 122 - 14 (Exhaust closing after BDC) = 108.
I think the calculator is correct. I'm questionion the chart above which shows the exhaust lobe center at 72 drgrees. There were several more charts in the same FC post that had really low exhaust lobe center degrees. Just wondering what the math is. I would expect the lobe centers to be pretty close to the same number. I the cam is installed straight up they should both be the same. Barry
Are you sure your looking at the right cams for your application? USA vs Euro cams for example? Don't know, just throwing a possibility out there.
They say the same thing (but there is a typo in the chart): The chart says the exhaust lobe center is 72 deg ABDC. The error is that the Author wrongly wrote "72 BTDC" in the summary table. (Note the two scales in the chart -- one for BDC and one for TDC. The Author wrote "72" which is correct for the ABDC scale, but could also have written "108" which is correct for BTDC scale) The calculator says the exhaust lobe center is 108 deg BTDC. 72 deg ABDC = 108 deg BTDC
