What is the purpose of the two divots here? Is this a T or TT valve? Thanks
Valve grinding tool pins stick in there.works better than the little rubber suction cups for sure.
Thanks Mack. I thought that might be the answer. FYI: I have a project TT plus lots of parts in a barn property I bought. I'll be posting it all for sale tomorrow.
There are typically two-piece valves which are known to come apart at inopportune moments.
Wasn't sure so didn't say it first but you really need to replace those. They come apart.
I believe Ford originally used these valves in T engines. Ford sold a hand operated valve grinder so owners could grind their own valves. Use to see those old valve grinders at farm auctions along with T tools and parts.
Not to nitpick (yeah, ME? Right). However in the vein of keeping terminology straight. Those holes are in the valve's head. The "face" of the valve is the smooth, round, angled, part that seats against the similarly ground edge in the block in order to seat and seal the passageway. Hence, "facing" the valves (a colloquial expression used in some regions of the country) when you use valve grinding compound and/or seating grinders or tools.
Good replacement one-piece valves were available for many years ('10s into the '70s) with the two holes for valve lapping tools to connect with. If they are in good condition, and the valve guides and seats (faces?) in the block are not overly worn? Those old one-piece valves are usually good and safe to use.
The "two piece" valves as used by Ford throughout nearly ALL model T and TT production, can only be reliably identified by looking at where the stem is connected to the head of the valve. At that point, the difference should be clear. The two piece valves have a (rolled? ground?) steel stem cast into a cast steel valve head. The transition involves a significant step between them. The so-called "one-piece" valves are actually (usually, but not always) made from two pieces of steel. However the steel stem and the steel head are welded together. The transition is fairly smooth, but may involve a slight bump. So-called "one piece" valves can sometimes break at the weld. However, that is rare. The "two-piece" type valves suffer from the effects of ambient moisture and more than a half century of ingress and corrosion. The effect, even in minute amounts, can force the head to loosen and the pounding of opening and closing tens of thousands of times can pull the head off the stem often enough to not be worth the risk of using them.
Many years ago, one of the few engines I ever saw that broke a "one-piece" valve was my dad's Ch**y pickup. Not one, but two cylinders were split multiple times the full length of the cylinders. Three rods were bent, holes punched through the cylinder head, camshaft visibly damaged, two pistons in about a hundred pieces, etc etc etc. ALL from one valve head. Still Such events are fairly rare with one-piece valves.
Now, I used to be fairly active with model T clubs and tours. I have seen at least a dozen two-piece valves break. Sometimes, at fairly low speeds? The damage is minor, valve replaced and tour continued. A few other of those model T engines were similarly totaled. One model T two-piece valve came apart, hit by a cast iron piston, decided to knock two main bearing webs out of the block and then break the crankshaft. What a mess.
I have for many years put replacing two-piece valves right behind replacing the Babbitt thrust washers in the rear end as a priority. Beyond those two things? There really isn't anything that I think needs to be "upgraded" on a model T. I think they are just fine the way Henry made them.