Forum » General Engine Building Discussion » Pitting on intake valve face

Pitting on intake valve face

General Engine Building Discussion

Forum Posts

Courses

Blog

Tech Articles

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads

Page 1
Author
103 Views

Hallo,

Have found all intake valves on my Yamaha supercharged engine to be full of little holes. A friend told me that would be usual on this engine.

What is the cause of it?

Attached Files

Most production valves are formed by hot forging, so fine surface irregularities aren't uncommon - https://www.youtube.com/watch?v=dMt1tqDI1nM

Most aftermarket and race valves use a similar process, but may be machined on the face and rear of the head as well, so would be expected to be a smoother finish.

Both may have a harder material welded to them to form a harder wearing seat when machined.

I was told New valves have a totally smooth surface it happens when running to become like that.

See post above - some are, some aren't. To be fair to whoever told you that, to the eye a new valve may seem to be totally smooth, as the irregularities may only be made clear when they fill with darker carbon/deposits and the higher surface around the pitting is polished when cleaning, so there's a high contrast. That you have taken a high resolution picture, and blown it up to many times the original size, just makes it more evident.

Your valves were 99.99% probability stamp forged. I say that because the code on the face is raised and that's impossible when machined but normal if stamp forged- if it were machined I would expect it to be stamped into the face or, more likely, engraved somewhere on the stem.

Thank you. That will help me for further decision.

Something else I should have mentioned is that there are also one and two piece valve designs with the two parts friction welded, this was done because, I understand, because it was to use the best seat material with the best stem material and/or it was cheaper overall costing out the materials.

Some performance valves are made in a similar way, all sodium filled are and some titanium and stainless have hardened tips friction welded to them - these are above the collet grooves, so don't compromise the overall strength of the valve.