Quote:
Originally Posted by FlowSpecialist
A nice timing for standard road cams is 111 LCA 3 degrees advanced which means inlet full lift at 108 ATDC and exhaust at 114 BTDC. On that basis the OE inlet timing looks correct and the exhaust was as you say a bit odd.
Valve piston clearance on a small engine like this is usually OK at 1.5mm but of course if you never over-rev it you can go a bit tighter. You'll have no margin for further experiments with cam timing though. I wouldn't retard the inlet cam just to get more clearance though. Do it properly and machine the valve cutouts deeper.
Dave
|
hi dave,
im happy with the timing i have now it gives me the characteristics i want ,but yes ,that ex timing was odd , my theory is that they needed to drop cylinder pressure ,so reduced the dynamic cr that way ,thus dropping nitric oxides (or watever their called) pollution . i
not bothered with future cam experiments ,just wanted to get the cr as high as poss ,without taking the bottom end apart .
how did vauxhall get away with the 1.04mm clearance it had with the ex at 99lca!!!
gulp , maybe thats why there are a few bent valves and broken cam belts on those engines .maybe ill have to stick with the 10.5 to 1 and move on with it ,much though it grates:
!