What should the clearance be on an exhaust valve?
The valves are closed ¾ of the time and while closed are cooled by contact with the valve seat, the exhaust valve relies heavily on valve seat contact for cooling, thus if the valve does not close fully the valve will over heat and burn. Valve clearance should be near zero when the engine is at
How are the clearances set on a double overhead cam?
However, on many vintage cars with single and double overhead cams, along with several late-model Toyotas and many motorcycles, the cam lobes push “bucket” tappets down over the valve stems, and shims of the appropriate thicknesses are employed between the tappets and the tops of each valve stem to set the clearances.
What happens to valve clearance as cam lobes wear?
As the cam lobes and slipper faces wear the valve clearance will increase. As the valves and the valve seats wear the valve clearance will decrease. The valves are closed ¾ of the time and while closed are cooled by contact with the valve seat, the exhaust valve relies heavily on valve seat contact for cooling,…
How much clearance do you need for a camshaft?
Camshaft, springs, buckets, retainers. Mixing and matching is a recipe for disaster. More than around 9.15 mm of lift needs cam lobe clearance. The head needs to come off, and it has to be ground to clear for a tall lobe, UNLESS its a 30 mm base circle cam, and under about 11.15 lift.
Can a cam increase exhaust P-V clearance?
Advancing the cam will increase exhaust P-V clearance. This may only be worth only a few thousandths of an inch, but this may be enough to keep the valves away from the pistons. Conversely, if the intake valve P-V is tight, you can retard the cam a couple degrees.
However, on many vintage cars with single and double overhead cams, along with several late-model Toyotas and many motorcycles, the cam lobes push “bucket” tappets down over the valve stems, and shims of the appropriate thicknesses are employed between the tappets and the tops of each valve stem to set the clearances.
Camshaft, springs, buckets, retainers. Mixing and matching is a recipe for disaster. More than around 9.15 mm of lift needs cam lobe clearance. The head needs to come off, and it has to be ground to clear for a tall lobe, UNLESS its a 30 mm base circle cam, and under about 11.15 lift.
How does cam position affect piston to valve clearance?
Piston to valve clearance is directly affected by cam position. Stated another way, changing the cam position directly affects P-V clearance. Since you will need a degree wheel and dial indicator in place to perform the valve drop method, it just makes sense to go that extra step and degree the cam.