Groovy Valves

[RecentConvert]

Hello folks. Long time, no see. I used to be a member here maybe 10 years back. I'm in the middle of rebuilding a Convert motor that did about 12,000 miles before the previous owner stripped the bike and stored it (dry) over 20 years ago. Now I almost have it back together again after vapour blasting but I noticed that the valves and seats have these concentric rings on them, rather than looking smooth and shiny.

Are these grooves normal? If not, how bad is it and can I clean them up by lapping them?

The right intake valve is the worst case but they are all dull and with some grooves. The seats are clean but weren't vapor blasted so I wonder if someone ground or lapped these at some point before me.










Bonus pic of the shiny, restored lump

[n3303j]

Almost looks like the seats were surfaced with a junk cutter.
Have them properly faced and valves ground to match.
Then you can run for 100,000 without concerns.

[John A]

Almost looks like the seats were surfaced with a junk cutter.
Have them properly faced and valves ground to match.
Then you can run for 100,000 without concerns.

Some shops don’t have decent small cutters and stones for the small seats but that doesn’t explain the valve faces unless they used dirty equipment. I learned to make sure the head shop had the stuff to do the smaller valves so they don’t try to get by on the crap they might have.

[larrys]

Really bad seat cutting there. I took a chance on the 20 carbide seat cutter kit online from India for $200. A Neway cutter set for my 350 Chevy boat motor was over $1K. The Indian cutters actually worked very well. I did three angle seats on the heads and am happy with the results.
Larry

[Moparnut72]

When I worked on radials in the aircraft shop I spent a lot of time with Neway cutters. It was hard work as I was doing blind cylinders. The is the heads weren't removable. I had to use a wobbly to get to the seats. It was tough to maintain even pressure on the seats with a long extension with a universal on the end. Even those antique engines had 3 angle valve seats. It was not uncommon to spend 2 days on a 9 cylinder engine.
kk

[larrys]

That's one valve seat/hour cut and lap. I can see that.
Larry

[RecentConvert]

Thanks for the feedback. I'll get these to a decent shop to be recut.

[tris]

Back when hand lapping of a valve with grinding paste was at thing IIRC you knew when you had a seal when a shiny line went all the way around

Is this what you're seeing?

[Moparnut72]

When I did valves in the aircraft shop, I did all of them, after cutting with Neway cutters, I ground them with valve grinding compound as the final step. I could tell if I was going to have a good seal if the contact area was a dull finish. I would double check with Prussian Blue and then with mineral spirits to make sure there were no leaks.
kk

[MattP]

Why is the engine tore down 2nd time? Only 12000 miles , many with over 200000. On them wire wheel the valves have the valves dusted off  in a valve grinding machine ,and lap them in should be fine, if not you will know if it dosent cleen up   the seats why remove move  any material  if you dont need to

[Moparnut72]

I didn't take any more material off the seats than I absolutely had to. Also needed to keep the three angle sizes equal to each other. Those old radials had pretty beefy seats though. Probably designed to be serviced numerous times, I never saw a burned valve or seat.
kk

[RecentConvert]

Why is the engine tore down 2nd time? Only 12000 miles , many with over 200000.

After the last teardown it was never ridden but it sat for 40 years. I took it apart to get it vapor blasted, to change the flywheel for the non-exploding kind and to try and strengthen the ATF pump drive. Otherwise, yeah, it would be pretty weird to pull it apart again.

[MattP]

look the guides should be   fine with 12 thou on it clean it up and run it. there is no such thing as perfect. It truley bothers me to se things replaced rebuilt that have over40 to over 100 thou life in them. it truely is a art aparently to wear some thing out, get the life out. I can count on one hand the people i know who can. anyway do a vrey accerat job indicating the touqconverter .