I have been in the process of reassembling my bike with the 351 kit. Some of you have responded to my "quick electrical question" thread that turned into something else, but I took it all down and started from the cyllinder up. Pulled the head and here's what my valves look like. They all look perfect except one. I would assume this is evidence of something but maybe not. It's not a crack and not residue but looks like a little pitting like what you would see on an antique gun. Should I replace the valve or is this okay? My piston face has no marks on it so I am not sure if the piston was hitting the valve as I thought since my cam chain was not timed right. Anyway, what do you think?

 

Tip the head so the exhaust port is UP. Pour in some solvent and see if it stays there. If it comes out a valve, then its bent. If not then you are OK.
do the same for the intake.

Anything I see in your pic looks fine. But I cant see where I need to.

David

David

 

Flip the head up on its side (Valve head facing down) and pour a shot glass of water down the intake runner hole. Let it sit for 1/2 hour and see if the valve holds the water in. No water should get past a closed valve. Do that test on all the valves.

If water comes out, the valve is not seated and may be bent.

 

You beat me!!!!

 

David, I will give that trick a try. Here's a close up of the area I am concerened about. I don't remember seeing this the first time I took this thing apart.

 

I have rebuilt many diesel engines, and just by looking at the pics, I dont see a problem, but I completely agree with the other posts. do the checks. If they turn out ok, I would just clean the valves w/emery cloth or steel wool. Im guessing that it is just carbon buildup.
Let us know what you find.
Thanks,
Jim.........

 

That's really not a machined area of the valve. I think what you see there is a rough place in the valve from when it was cast. Might take a little emery cloth and sand it a little, but I wouldn't loose any sleep over that mark. Just make sure those valves are sealed before you put this all back together again. Hope your garage is heated!

PS: When this runs we all get a free ride "bitch" don't we?

 

Okay, I put some chevron carb cleaner stuff in the intake side and tipped it up to see if those valves leak. After survivor is over I will flip it and try it on the exhaust side. The valve in question is one of the larger ones on the intake side.

 

No heat in the garage here in Utah. It sucks.

And without a doubt whoever wants a ride can have one. Hell, you can ride on it wherever you want.

 

That is good test.
I've worked on "vintage" bikes that are notorious for not maintaining a good valve seal. This test shows the issue every time.
Then the valves get lapped, or replaced if needed, and I repeat the test.
Motor isn't re-assembled until all valves show no sign of leakage.
I use denatured alcohol and leave it sitting in the ports for overnight.

Those marks on your valve do look like it's left from the forging. I've seen valves like that before, I think it's normal.

--
Mikko