Backfiring and now discovered stuck valve

Bobant

Bobant

Member
Decided to check new plugs tonight and 3 looked perfect coffee color and one was all carboned up, 2nd one from the back. Checked too see if there was any compression just by putting my fingers over the plug hole and there was none. I did not have a fitting big enough for my compression gauge but didn't need it anyhow. Took the valve cover off and 4th valve from the back was stuck open. Tried to manually move it down and it did come down ,but it is very tight. When it goes back up it does not come down on its own.
Question- is that an exhaust valve or a intake valve? It is very tight.

Is my next move to remove the head and take the valve out? This is all new territory for me? I don't see any alternative.

I have been using Les Andrews handbook as my guide.
As stated in an earlier post of mine the car was running ok but would backfire at speeds over 30 . I guess the stuck valve would explain a lot of my troubles.

Any words of advise would be greatly appreciated. I am doing this myself with little experience. In case I get stuck is there any good mechanics in the Chattanooga area that anyone would recommend if I get beyond my comfort level? I like doing it myself but I also don't want to do any further damage.
 
if it back fires out the tail pipe its an exhaust valve if out the carb its an intake valve, try squirting some marvel mystery oil on the valve at the guide and put some in the cylinder and let set over night, if you get things freed up and running use 4 or 5 ounces of marvel mystery oil in 10 gallons of fuel, if the valve can be freed with out taking the head off that should do it, if it does do the trick keep putting mmo in when ever you fuel up, 2 1/2 ounces per gallon, if you do have to pull that valve chuck it up in a drill press and polish the stem with fine emory cloth soaked in oil, you can polish the inside of the valve guide with a valve lapping tool, put a little valve lapping compound on the valve stem and just a little down the guide, put the lapping tool in a drill press and on top of the valve head and run it up and down the guide a few times, put a rag in valve chamber under the valve your working on to trap any compound that may fall in there, when done make sure you clean all of the compound out of the guide, off valve stem, and valve chamber, this step is very important to make sure none of the compound gets into the engine and causes damage
 
With the valve stuck open you should be able to spray Kroil through the spark plug hole onto the valve stem. Also spray the valve stem at the bottom. Keep working the valve up and down, and it should free up without removing the head. Sea Foam or MMO added to the gas will help, as mentioned.

The 4th valve from the rear is an exhaust valve.
 
I had that issue with my coupe about a month back. I did a compression test and found that one of the valves in number two bore was sticking open about half the time. Compression was fine at about 95 psi when the valve closed, which was the same as the other three bores. I poured about an ounce of Marvels Mystery Oil, (ATF automatic transmission fluid would work) maybe two, in the cylinder through the plug hole, put the plug in that hole, turned the engine over a few revs, took the plug out and poured some more MMO in the plug hole and let it sit over night, Next morning I put the plugs back in, put a piece of cardboard under and behind the tail pipe, started the car and drove out to meet some friends for coffee, I filled up while I was out and added two ounces of MMO to the gasoline and haven't had any sticking valve problem since, A side benefit is that the needle valve in the carb. hasn't stuck once since I put the MMO in the gasoline. Thanks to this forum I have a smooth running engine that required only the removal of a spark plug. I hadn't appreciated the benefits of MMO until I got on this forum. Now I gargle with it each morning. NOT! The cardboard had a wet, oily, black spatter over it from the startup, but by the time I had gone for fuel, coffee and back the MMO wasn't leaving a trail.
 
Has the car sat long enough for most or all of the gas to evaporate out of the tank? If so, it has left behind a thick gooey type of varnish. Fresh gas will slowly dissolve this goo, but it does not burn! Instead it for some reason settles on the exhaust valve stems and is sticky enough that it holds the valve open, either completely or intermittently. Carburetor cleaner spray, such as Gum-Out, will usually dissolve this stuff, but I've had a few engines where I had to actually remove the valve from the guide to get this stuff off! If your fuel tank has this junk in it, the problem will keep repeating itself until the tank is clean!
 
Yep, its the new gas with ethanol in it....isn't it wonderful. If you don't use up the gas\
within 3 months it goes bad and does all kinds of great stuff to your motor. The most
common one is stuck valves.
The only ones happy about it are the corn growers.
 
We always have taken about a small cup of mystery oil, start the car and with the oil in one of those old time oil cans like a Model T one, put a small plastic tube, or a hose on the spout, and stick the hose in the carb. with the motor running and turn the top loose just so it will suck the oil out of the oil can. when it starts smoking real good, kill it with more oil, or shut it off.

Leave it 24 hours, its works every time, I have done that all my life, and my dad before me.

Valves in many engines get stuck over winter.

Herm.
 
Update on valve job. Took valve cover off, then head. Valve is stuck that tight that I struggled to move it. It is very tight no matter how high I have it pulled up. Project on hold now waiting for valve seat removal tool and assorted new parts. This is my first time ever doing this. By the way they are the mushroom style valves. Valve is so tight that I had to put pry bars on both sides of valve to move it. I did protect the head surface.
1. What would make a valve stem so tight no matter how far it is raised? Is that common?
2. Do I have more surprises in store when I try to knock the seat out using the proper valve seat removal tool?
3. Anything special I should know when installing new two piece valve seat?
 
I don't know if this will help, but I'll share in case it does. When the rebuilt engine for my old 28 Huckster arrived all the valves were too tight in their valve guides. I did not want to deal with the hassle of contacting the builder and shipping the engine back, so I took some valve grinding compound I had on hand and lapped each valve with its guide until is was silky smooth. Making sure I cleaned off all compound I reassembled and the engine ran beautifully idling so slowly you could count each "pa - chuck, pa - chuck, pa - chuck"!
 
I wouldn't have pried the valve up, but I would spray Kroil on the stem and use a punch exactly in the center of the valve, then carefully tap it down. Watch the tappet to be sure it isn't pushed up by the cam lobe. After you tap the valve down onto the seat, then crank the engine over 2 turns to raise the valve again, and keep spraying Kroil and repeating this until the valve is free. If it doesn't free up this way, then remove the keeper, spring, and valve.
 
If your engine has original mushroom valves you hafta remove the valve guide. The parts houses sell them, I have the one that hugs the elevated valve then you give it a smack with a lead hammer to drive the guide out into the valve chamber. Just an fyi
 
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