Red's Engine Talk
Valve Train May/June 2004
Originally published Nov/Dec 1998
The Early Ford V8 valve train is a direct descendent of the Model A: split guides with mushroom tipped valve stems. One advantage is the V8's removable guide retainer instead of the Model A's integral flange, so that you can assemble the valve/guide/spring and retainer outside of the block and install it as a subassembly. This is aided by the bump or step on the valve stem to help push the guide down as the valve is pushed in.
For 48 trucks and 49 cars the big change was a solid one piece guide with a straight stem valve and conventional split locks. This eliminated the need to keep guide halves identified to each other, almost eliminated valve sticking problems, and improved oil control by eliminating the split line, allowing tighter stem to guide clearances and allowing the use of a valve guide OD to guide bore seal, which fits into a groove around the guide. Ford used these seals only on the intake so that the exhaust guide could be solid, with no groove, for better heat transfer into the block.
Aftermarket suppliers make only the intake style. It is probably better to use guide seals only on the intake even though aftermarket exhaust guides also have the groove. The exhaust heat can "vulcanize" the seal to the guide bore, causing problems in removal.
The next change was in late '51, when the spring was shortened and used with a two piece retainer. This allows valve rotation and may extend valve and seat life. The later valve trains may be installed in the earlier blocks to obtain these benefits. Many vintage suppliers have these parts available as kits, which include all of the necessary pieces to make the change. This changeover costs quite a bit less than a set of the early style parts.
When you must remove a valve Train to clean and check a block, or to do a valve job, it helps to have the right tools. A long bar with forked end(s) and a bar with a hook for pulling guide retainers are near the minimum tool requirements. Penetrating oil, other tools, and a colorful vocabulary are sometimes helpful. lf you can pull the guides down toward the centerline of the block, you can pull the guide retainers easily. This is usually done by engaging the forked tool in the bottom of the guide in a groove designed for this purpose. The split guides should be oriented with the parting line transverse to the block centerline so that both halves of the guide may be pulled down at the same time. Remember that when reinstalling split guide assemblies. If not, the hooked tool, engaged in the hole in the tab of the guide retainer, will usually get them out, usually bent and not reusable. Sometimes you must drive the guide down to get the guide retainer out. You may have to break the head off of the valve, but valves are cheap compared with blocks.
Once you get the guide retainers out, the guides have to come out. They can be pried with the forked bar from the bottom, or from the top, or both. Or if the valve has been broken and removed, the guide can be driven down from the top. When prying from the bottom, use a stop of some sort so that if a valve assembly flies out it doesn't ruin a window or a paint job. Don't pry the valves up with a fulcrum on the upper side of the block deck, a gasket surface. The deck can be broken or dented adjacent to the oval water holes above the valve seats quite easily. lf you must pry the valves up from the top, place a plate in that area of the block to distribute the force, or use a special Cclamp tool made for this purpose.
A conventional valve spring compressor can be used to take the subassemblies apart for cleaning and dimensional checks. Remember to maintain identity on the guide pairs for 32-48 if you hope to reuse them. Light safety wire, tying them together through the guide retainer groove, is what we use.