VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Sticking exhaust valve

Today took my car for an inspection sticker. On the way back there was a long straight and I decided to take it up to 50-55 for the first time. After about a minute I started getting an intermittent skip and lost of power. When I got home there was also a skip at idle. First took out the plugs to check for any color or evidence of fowling. Then took off the valve cover. Found the exhaust valve for #2 stuck down. First tried tapping it with a screw driver and nothing. Then got a little hammer and it popped up some, but not all the way. Tapped it some more and it came up. Then cranked it over with the hand crank and it stuck down again. This time a light tap with the hammer and it popped fully up. Rotated the motor again and it stayed down. A tap brought it up. I then light tapped on the valve retainer to try and rotate the valve some. It seemed to turn some but not a lot and I wasn't trying to force it. I can say now that it no longer sticks down at all though. Can the valve be fully rotated as it sits? I would think so but wanted to asked first. Almost every one of my valve's retainers face across the length of the engine including the one that gets stuck.
Can anyone speculate why the valve would stick in the first place after all this time running. Car is running normal temp on the water gauge. One thing I've noticed is the head has paint discoloration at all the exhaust port areas like the exhaust manifold where the paint has burned off. The paint is not burned off the head but it is definitely browned a fair amount. The plugs (new) are not really brown but the electrodes are not snowy white either. Can these cars run too lean? Could this be a reason?

are you using a little atf in your fuel ? it helps the new fuel is dry need a little help there are other additives but atf is the most economical for me use it all the old engines. hope this helps

Not using anything. How much do you use to a gal? Does it help with issues like this? Curious on what could be the causes of a exhaust valve sticking.

Either the guide is too tight or there is carbon build-up on the valve stem. Pour some MMO or ATF thrugh the carb. with the engine running and add the same to the gas. Like a pint to 10 gallons.
You could also squirt some on the valve stem of that sticking valve.
I would not rotate the valve.

No firm answer here, but had the same problem with 2 engines in the past. One was on a new BMW R-60 motorcycle that ran fine for the first few hundred miles but started missing badly enough that I had to be trucked to a dealer. They pulled the heads, reamed guides and all was well after that. Second eng was after a complete rebuild on a 41 SC Case, ran great for the first 20-30 hours but when loaded with pulling disc to close in plow furrows, same thing with that eng. Pulled head and reamed those guides and all was well also. The difference was that I had the guides knurled instead of replaced. Never knurled guides after that. Sounds like a little atf might help you there as suggested.

Paint burning off at exhaust ports at head is normal. Sounds like your plugs burning ok to me from what I have read.

Am sure all will turn out well for you from what I have read in your posts. You have done a bang-up job on your resto.

Jim.

Thanks JDV, I'm going to try the ATF. Can't the valve completely rotate in it's seat? I know other valves can but not sure on these engines. I'm going to try and look at some exploded drawings. Not sure if rotating it some will help also. I know that it shouldn't matter but I'll try it anyway if I can.

Chistech,

That's some interesting advice you got. I wonder what a lubrication engineer would have to say about it? I also wonder what "dry" gasoline is.

If the valve stem is carboned up it's hard to imagine how adding more oil will remove rather than add even more carbon. It's not a 2-stroke engine that requires "premix".

There is a proven product for cleaning combustion chambers and intake valves of deposits. That is Techron. It takes many applications and doesn't approach the effectiveness of actual disassembly and cleaning.

If you pull off the intake and exhaust manifolds you will be able to look into the ports and see the valve stems and the backs of the valve heads. Then you'll know what you're dealing with.

Knowledge is power!

JDV,

"Knurling" valve guides is a totally Mickey Mouse band aid for worn out guides. In David Vizard's highly regarded book How To Rebuild Your Small-Block Chevy Vizard mocks knurling as being very short lived.

Ray W

The later truck engines had positive valve rotators. If your valves have been in this position for a lenghth of time and you rotate them they could loose their seal with the seat in the head.....it is not adviseable or necessary.

I agree with Chevgene. Not necessary to rotate the valve. As in my old Case engines, there were no rotators on valves. Ran many thousands of hours without a valve problem. I may be wrong, but your engine is new enough that I doubt that you would have enough carbon build up to cause valve to stick. As Gene stated, perhaps a bit of extra lubrication may help.

Best to ya.

Jim.

I went out to the garage and rotated the engine with the crank. The valve was not sticking. Started it up and withing two minutes it started skipping again and the valve stayed stuck down. Shut the motor off and tapped it with a light hammer and it popped up. I did try rotating the valve to check the stem and it didn't want to go more than 180D. I ran the motor again and it did the same thing, ran for a minute then started sticking again. I flooded the valve stem with some marvel mystery oil and left it for now. I have a bad feeling I'll be pulling the head. Should I pull the manifolds and have a look at it?

Do you have a weak or broken valve spring?

Jim,

I found Vizard's actual words about valve guide knurling:

"The cheapest method of refurbishing is to knurl the guide bore. On a Chevy this may last 2,000 miles before it is as bad as when you first started".

That was published in 1968, and it was not news then. It's sad that unscrupulous machinists still use that "fix" that was discredited decades ago. Thin wall bronze bushings in the valve guides and regrinding the stems on a centerless grinder make the fit as good as new with long term durability.

Head reconditioning has come a long way since the days of guide knurling and seat grinding with a hand held Souix grinder.

Chistech,

If you're contemplating pulling the head why not look into the ports first?

Ray W

It's not broken but I don't know if it's weak. It's hard to tell but it will run for a minute just fine until the motor warms. It's like the valve is expanding once warm and sticking in the guide if that makes sense.

I figured I would do that first before pulling the head as the manifolds have to come off anyway. Not sure if I can get some lube on the valve stem from the port also.

My valves all have green (silicone?) seals around the stems covering the top of the guides. The exhaust ones are kind of bell shaped and are tight on the stem and the larger "bell" is tight on the casting of the head around the guide. The intakes have a similar looking one but no bell and have a spring wire around them to keep them snug on the stem. They do not cover the top of the casting/guide area.
Last night I slid them all up and flooded Marvel Mystery oil on top of the guide area. Today I ran the motor and the valve is not sticking as of yet. I spoke with my brother (a long time mechanic) and he feels there could be a small piece of carbon stuck to the stem. He is coming over later tonight and we are going to spray water in the carb while at a higher throttle to de-carbonize it. Hopefully all will work or continue to work.

Will be anxiously awaiting the results.

Jim.

Didn't do the water spray thing yet as my brother and I haven't been able to get together to do it. But after it sat the night with the Marvel Mystery oil on the stem, it's been good. I took it out for a decent ride today and it ran perfectly. So far, so good.