What's Up Top?
We don't give cylinder heads and valvetrains enough of our attention, but these are areas where engines fail most. Because valves and springs do one of the toughest jobs inside an engine, they mandate our every attention. Valve-stem-to-guide clearances must be spot on-not too tight and not too loose. MCE Engines recommends a window of 0.0015-0.0025 inch on stem-to-guide clearances. For intake, go with 0.0015 inch. For exhaust, push it more toward 0.0025 inch because the exhaust valve runs much hotter.
During assembly, Marvin uses Comp Cams assembly lube No. 153 over Dow Corning dry film lubricant No. 321 for ideal valve-stem lubrication for that first firing. Valve clearances can bite us in the butt if we're not diligent during assembly. Again-more of that mock-up stuff. Mock up your engine's cylinder heads and check clearances. How close are the valves to each other? How much clearance is there around the valve heads? What is piston-to-valve clearance? Have you checked all of them? Just because clearances are acceptable at one bore and chamber doesn't mean they will wash with the rest. No two chambers are the same, so don't expect them to be.
Marvin blueprints every part of every engine he builds. Valvesprings are massaged to eliminate sharp edges that cause friction. Then, valve springs are coated with Dow Corning Dry Film No. 321 to eliminate friction during initial start-up. Dow Corning's 321 Dry Film lube is a good lubrication foundation for startup. Then, Marvin coats it all with Comp Cams assembly lube during assembly. | 
Valve-to-valve clearances are checked-never to be smaller than 0.060 inch. Even if you have virtually no valve overlap, you still want a minimum of 0.060 inch between valves at the chamber seats. | 
Valve stems are coated with Comp Cams Assembly Lube to ensure lubrication during startup. |
Here, Marvin checks valvespring installed height to ensure the engine will reach the cam's rated engine redline. | 
Valve-to-piston clearances are checked using clay in the valve reliefs as shown. Marvin checks valve depth in the clay. Clearance is 0.060 inch intake and 0.100 inch exhaust. | 
One thing we rarely get right in engine building is port match. Bad port matching robs power. It can also make engines run rough. Check out this MCE port match-perfect alignment for reduced turbulence. |
MCE Engines secures roller tappets like this, using safety wire to secure spider fasteners. Parts are polished, and the valley is coated with GE Glyptal paint from Eastwood to improve oil return flow. | 
Schneider shaft-mounted roller rockers are designed to take a seven-grand blast. What's more, they're easy to adjust and maintain. | 
Marvin performs valve adjustment by the 427W's firing order. Valves are adjusted at the lobe's base circle for best results and accuracy. Lash is 11/42 turn clockwise from zero lash for both intake and exhaust with a hydraulic roller cam. |