Bonjour!
I have two flat tappet camshafts. Different manufacturers, one solid, the other hydraulic. different applications but same engine series (BBM).
I have found both camshafts have a a base circle that drops .001" approximately 50 crankshaft degrees (25 camshaft degrees) prior to the ramp.
Q. #1. Is this drop prior to the ramp what is referred as the heel? I think the answer is yes, but seeking a second opinion is always a good thing.
Q. #2. What's it's purpose? To put oil under lifter base?
Q. #3. When mapping a camshaft should the dial indicator be zeroed at the base .000, or the drop (heel) prior to the ramp? I assume the base and not the heel, for valve adjustment EOIC puts the lifter at the base and not the heel.
Q. #4. What is the typical length of the take-up ramp on a solid (mechanical) 7*, 8*, 15* of camshaft degrees??? And, again is this measured from movement zeroed on the heel or zeroed on the longer base?
OK, Thanks.
1). The drop is called a clearance ramp. The heel and the base circle are one in the same.
2) To slow down the lifter on the closing side to prevent valve bounce. On the intake side it is to promote stabile valve opening.
3) At true base circle, but I guess it depends on what you are trying to map. Lift, duration, what?
4) I would imagine that depends on the design (hydraulic, solid,roller) intended use, spring pressure,,etc.
