The service manual for my 3T1 D7 (3T14387) says that intake valves have a small groove around the top of the valve stem to distinguish them from exhaust valves.

The used head I removed from a 3T1 in a salvage has the intake/exhaust valves reversed.

The valves appear to be the same size and physically interchangeable. Does anyone know if there is indeed a difference in these valves besides the small groove around the stem?

I never thought about it but I,m guessing they are both made out of different material or tempered different to withstand the heat as with the ex. valve.I can,t remember the size of the valves on the D7 but most times the in. valve has a larger diameter head than the ex.does.

I recently found an intake valve that had run in the exhaust port of a D2. The valves look the same but are stamped on the top exh. or int. somebody just screwed up.

Anyway, that intake valve showed some serious heat treatment--bluing way down the stem. I'd say the steel is different on that basis. I was afraid to reinstall it, bought another intake valve and used the exhaust valve that had been running in the intake port for exhaust. I've no idea whether it would be soft, or brittle, or heat checked, or OK. I could just see that it was changed.

They are definitely a different part number for intake and exhaust valves so I think it would be safe to assume they are of a different metallurgy and not to be interchanged.

Go to your web browser, and type in Stellite. This is the alloy that is normally used in the manufacture of exhaust valves.

Although the valves are just about identical with the 1/2 stem and same angle to the seat area, CAT did make an effort to make it near fool proof with the location, marking the face and also the stem, the price of the exhaust valve is often about 1/3 more expensive than the inlet so something must be made of better metal, but I am pleased to see you spotted the snag and put up a querry,

tctractors

Sounds like it was just a mistake. I decided to correct the mistake, touch up the valve seats and re-grind and insert some other used valves that I had.

Unfortunately, I found a crack on one of the exhaust valve seats after touching it up. The fun just never ends..... Now I have to learn how to replace a valve seat. I started by TIG welding a bead around the inside of the seat to shrink the seat. Next, I will press out the valve guide and see if I can reach through the valve guide hole and drive the seat out.

An easy way of getting those seats out if you are going to fit new valves is to grind down the outer dia' of a scrap valve head and weld it into the the seat, let it cool then a few taps and it falls out, to insert the new seat, I press in any new valve guides first then get the seats out of the freezer and press them in also, I have made myself press tools on a lathe to make this job very simple and easy,

tctractors

tctractors, you make that sound easy.

Do you need to heat up the head before pressing in the new valve seat or does putting the valve seat in the freezer shrink it enough to allow it to be pressed in at room temperature?