Raymond,

Well, specifying valve lash (clearance) is not straightforward. If the valve and cylinder head had the same temperature the valve lash would increase with temperature, due to the higher thermal expansion coefficient of aluminum (cylinder head) vs. steel (valve). Although the exhaust gas heats the exhaust ports, the exhaust valve likely gets quite a bit hotter, but maybe the net result is no clearance change between hot and cold engine.

The Jalpa engine has sodium filled exhaust valves (if nobody has changed them), which runs cooler than solid valves, so everything equal they should likely have a slightly smaller clearance than the solid valves. Did they change from solid to sodium filled exhaust valves from the Urraco to the Jalpa?
The early 4L V12 engine with solid valves has a specified valve lash of 0.25 mm on both intake and exhaust.

Lastly, when I measured my Jalpa’s valve clearances they were very close to the specifications I gave in the previous post, so I left them alone and they have worked fine since (even with 10 psi turbo-charging).
If I ever were to change the exhaust valves to solid stainless, I would increase their clearance to 0.45 mm.

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Jalpa TT #ELA12161
Espada #8356