Packard Forum Index » Post-War (1946-54)

Just got my cylinder head back from the machine shop. 288 AT from a 1951. They removed about 14 thousandths to correct warpage. I know I need to check clearances on the head before I reassemble. Could someone walk me through the process or point me to a thread that could help? I know it involves clay but I can't find anything detailing how this is done on an inline flathead. I have a few specific questions as well.

Do you do the check with a new head gasket installed?

Everything I've read says to replace hydraulic lifters with solid lifters as hydraulic will cause false readings. Does this apply here? Because my engine does have hydraulic lifters.

If seats have been ground or changed or valves replaced there is a special plug gauge to use in checking valve stem length and ultimately clearance for the hydraulic lifters. There needs to be a specific amount of clearance between the stem and lifter to ensure the lifter can pump up a bit yet not drive the valve into the head. That is for the standard non milled setup. The Pacific Northwest Packard club region has repro gauge tools for sale.pnwpackards.com/styled-2/index.html Instructions for use are in the SM.

On milled head checks, after the stem length is correct and lifters are pumped up into a working state I believe most place a bit of clay on the valve edge or the lowest point of the combustion chamber directly above where the valve would hit. Place the head on the block without gasket and turn the engine by hand watching for any movement of the head. If none seen, carefully remove the head and check for any place the clay has been mashed thin or metal shows thru. Leaving the gasket off is the worst case condition so if everything checks OK without the gasket then with the gasket in place and head torqued there should be an extra margin of clearance.