Stock Harley Davidson Valve Tip Protusion With Stock Valve Size
The tip lenght on the Sportster 7mm valves is .100” versus .070” on the Twin Cam 7mm valves but the spring spacing is the same because the protusion is higher on the Sportster.
All these specifications apply to stock cylinder heads
On heads with oversized valves and modified camshafts, you8 may need to sink the valve seats deeper for valve to valve clearance and this may result in a higher protusion. The engine builder needs to decide what minimum spacing he needs between the intake and exhaust valve and then he may have to sink the seats to get the correct valve to valve clearance at TDC lift.
Stock Head Thickness
Evolution Big Twin: 3.750” • Twin Cam Big Twin: 3.750” • Evo Sportster: 3.700”
Heads with oversized valves, modified camshafts with longer overlap, or heads that have been milled for increased compression require special attention to valve to valve piston clearance; pistons valve pockets need to be large and deep enough to prevent collision with the valve. Also adjustable push rods might be required if the heads have been milled or if the valve tip protusion is higher than the stock specifications. All valve spring spacing must be adjusted to get the correct spring pressure.