I finally found some time to start taking my blown nailhead engine apart. Recall that I bought the car from a friend and it was reported to have "top end oil pressure problems". So I just pulled the engine out of the car, and with it sitting on the engine stand I started the teardown diagnosis. The passenger side valve cover was lifted off and this is what I found. One broken rocker shaft, several very dry and hot rockers, burned oil smell and debris all over. Several valves are very loose, the guides are wasted, I can move them sideays with hand pressure. I pulled the valley pan and the cam seems OK, no obvious flat lobes or worn lifters. I did find the lifter for the broken rocker had broke the retaining clip for the plunger, the clip was distorted and a piece was found in the block. I pulled the oil pan and did not see any major problems with the bottom end, only a few small pieces of junk in the bottom of the pan, the pieces appear to be aluminum and from the broken rocker arm. The cylinder bores all look good, no problems noticed when I pulled the bad cylinder head. I certainly don't want to buy new pistons as it has custom forged blower pistons, and looks like I can leave these alone.
oil problem I am not sure if this applies to nailheads, but on some other V8 engines the oil for the rocker arms is fed through a hole in the rear cam bearing. If the cam bearing is put in wrong and the oil hole is not lined up with the hole in the block the rockers get no oil. Brian
On nailheads, the oil to the lifters and rockers is supplied from the front cam bearing. So an improperly installed bearing could starve the lifters and top end of oil. There must also be a groove cut into the front cam journal. Oil then flows thru a drilled passage in the head, to the front rocker pedestal, via oversized bolt hole. Stock rocker arm shafts need to be oriented with the notch (at the end of the shaft) pointed up. If your damage was limited to one side, check oil passage in block, head gasket, rocker shaft (is the front pedistal different?) and shaft orientation. Maybe you can spin the oil pump to see if oil flows freely to the head. Should be a hell of a nailhead when it's back together!!!
Hi Terry Just a little information that might help you. In the april 1966 issue of Hot Rod magazine there is an article on Blueprinting the BuickNailhead. Infact here are two different articles on the Buick Nailheads. Good ideas and reading. Jim Schilf / palbuick@aol.com
