So, I'm cleaning up the heads on my 292 as I put it back together. As I'm removing the valves I notice that there are umbrella seals only on the intake.
The Fel-pro kit has 16 seals. So I got confused. Below is what AI told me. I thought I would confirm with the experts as well has have this documented for others that come along later.In the world of Y-block restoration, you’ll find that the factory standard was typically to run umbrella seals only on the intake valves.

While it’s tempting to use every part in the gasket kit, here is why you should consider sticking to the intake-only setup:

1. Lubrication of Exhaust Guides

Exhaust valves operate at much higher temperatures than intakes. Because the exhaust side is under positive pressure rather than vacuum, it doesn’t "suck" oil into the cylinder the way the intake side does. Consequently, the exhaust valve stems and guides rely on that small amount of oil mist for lubrication. If you seal them too tightly, you risk the valves sticking or the guides wearing prematurely due to heat and friction.

2. Vacuum vs. Pressure

The intake valves are subject to high manifold vacuum, which actively pulls oil down the guide and into the combustion chamber, leading to blue smoke and carbon buildup. This is why the intake seals are critical. The exhaust valves generally push spent gases out, which naturally helps keep oil from entering the guide.

3. Modern Gasket Kits

Companies like Fel-Pro often include 16 seals simply to provide a "universal" solution for various head configurations or for builders who have machined their guides for modern stem seals. On a stock Y-block head, those extra seals are usually best left in the box.
Recommendation:

• Install the seals on the intake valves.
  
• Leave the exhaust valves without seals, unless you have specifically had a machine shop install bronze guides or narrowed the clearances significantly.
  

A little bit of oil on the exhaust stems is a safety net for a vintage engine—it's much better to have a tiny bit of oil consumption than a seized exhaust valve.

 

AI strikes again - kinda right, but also very wrong.... Various Y blocks used different exhaust valve types depending upon which specific y-block block/head/valve configuration was built - rotating and free-turning. The rotating valves uses the "umbrella"; The free-turning do not. This also overlaps with the introduction of sodium filled exhaust valves which had larger diameter stems (and thus different head revisions). The kit comes with 16 seals in the event your application requires all 16, but not all do. Now, to determine your setup to ensure your block/heads/valves are compatible and determine if you should use 16 or 8 umbrellas.

 

You make an excellent point about AI. It can give some great information it can also be very confidently wrong.
Here is my head with two valves removed. It only had seals on the intake, so I would assume that is the best way to put new ones in.
My current ones are hard as a rock.

 

Joe if I recall correctly that motor came from a BIG TRUCK. Your photo looks to show the exhaust valve stem larger than the intake, indicating it's sodium filled. I'm no expert but have been told that sodium filled valves should be handled with care.. in the past they were used to dissipate heat better than solid valves mainly used on diesel, and big truck engines.

 

Good info BJ. It's actually the exhaust valves that are probably sodium filled. The larger comment threw me a little. The head of the valve is larger on the intake, but the shaft on the exhaust is larger (indicating sodium filled)

 

Sorry trying to get loaded to leave for Pigeon Forge and didn’t make my self clear.

 

Just an interesting tidbit where Ford documentation tells you to discard sodium valves by burying them or sinking them to the bottom of water bodies and to not deal with them as traditional scrap metal.