I am pulling the 216 on my 1951 1 Ton to do a rebuild. When I put the truck on the road ten years and 40K miles ago, I did an in place rebuild. At the time I didn't have the space to pull the motor but now I do. Over the years I have replaced the main bearings and the cracked head. The motor has worn cylinders but runs well. One of the cylinders has been honed out some by a previous owner and so there is some piston slap in that cylinder. I plan to have the block bored and tanked. I will be putting aluminum pistons in it.
Now here is my mystery. Right from the start the oil pressure reading was nearly pegged when cold or at least well over half scale. After about twenty minutes of driving it will read 7 lbs on the highway and around zero at idle. I have replaced the oil pump and the oil distribution valve. The feed to the rockers has the proper restriction. When I replaced the main bearings I shimmed them so the clearance was at minimum and this made no difference in the pressure. The only thing that I haven't attended to is the camshaft bearings. So when I have it apart I will be looking to see if there is a cause of this low oil pressure.
As a contrast the oil pressure in my 1938 Master 216 has always been excellent. Even when the main bearings were really sloppy after I bought it, the oil pressure was excellent.
