Philippe, don't know if you are already familiar with the procedure? But be damn sure you have oil flowing to all 16 Rockers by Priming the Oil Pump prior to closing the Top. Pump runs counter clockwise and you can get the Tool or use a 1/4" Socket with an extension. Before you close it when you have assured free flow poor 1/2L Oil over the Valve Train on either side.
And use low viscosity Mineral Oil in your fresh rebuild Engine like 10W-40 or 5W-30 with the additive for your Flat Tappet Cam.
Sorry if you already knew!
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.