The Stovebolt Site Forums The Shop Area Engine Shop (Partially) Stuck Valve

I just picked up a '39 1/2 Ton that's been sitting for many years. The engine is free, thankfully, but I noticed I had one stuck valve. I assume it was just stuck in the position it had been sitting in. I pried it up by the spring with a screwdriver then rotated the engine hoping it would go down alright and then pop back up. It took doing this many times to get it loose and it now goes up and down on its own just fine, except for the fact that it only opens about 90% or so. My plan is to keep prying it up the rest of the way and hoping that the consistent back and forth movement will free it up so that it's as good as new. My other thought is that I can get a battery hooked up and keep cranking the engine and that with the consistent up and down movement it will hopefully loosen little by little until it's 100%. Any other suggestions or concerns, though? I've been spraying Blaster on it each time I move it.

Thanks.

Dan

Usually just spray lots of Blaster on it, and keep working up and down....
John

There's probably a ring of rust on the stem. A new valve guide is $6 and new valve is $15. New head gasket maybe $30?

A little more work, take the head off, replace the valve and guide.

Shouldn't take more than an hour with the proper tools.

I'll have to read up on the process. I don't necessarily have the proper tools but know a guy that would.

Thanks.

Dan

Did ya try marvels mystery oil? That stuff works great

PB Blaster is good stuff. Use something like that and it should be back in no time. Good luck!

both marvel mystery oil and pb blaster are great, i have both in my shop and use them constantly.





Indy

If the valve is not opening up all the way, something is wrong and probably the pushrod is bent. If that is so it will probably fall out of position if you run the engine.

Good point truckernix. Probably should pull the side cover off and check that out to be sure.

John

Is this a good guide for removing the head?

Sure seems like an all-day project to me, mostly because my intake and exhaust manifolds don't look like they've ever been removed. It'd be a real challenge to get them off without braking any bolts or studs.

Dan

No need to take side cover off to check the pushrod, just turn motor until you are at tdc and then use finger tips to turn the pushrod. You will see if its turning true or if its bent.

You could remove the head and leave the intake and exhaust manifolds on it, but it makes it a little lighter and easier to handle. The head is fairly heavy.

John

no, it really isn't an all day job. i can personally take the head off and reinstall it in less than 20 minutes, maybe it's because i have done it so many times . once you do it on a straight six, v8's seem insanely hard .



Indy

Well that's good to know, but it will definitely be my first time so I expect I'll have a little more difficulty. But it sounds worth it to check out what's happening with this valve, and to give all the chambers a good cleaning. I assume I can soda blast everything without doing any damage, right?

Dan

Yeah you'll probably have some carbon build up on the tops of the pistons and the combustion chambers. Give you a chance to see how much ridge is in the tops of the cylinders too. Give you some idea of the amount of wear in the engine...

John

I don't want to jinx you, but I have never had any of the bolts snap while removing the manifolds on several 216s and 235s. I haven't been so lucky on just about every other make of engine.

Use PB Blaster or equiv on each nut and bolt. Let it soak a few days, then apply more. Let is soak a few days. Its ready and your chances of breaking anything are significantly reduced. I use that procedure for unfreezing motors. Take your time, enjoy the process. Its the best part! Good luck

Maybe I'm quick at it but taking the head off the 270 in my CCKW to replace a head gasket was about an hour start to finish.

The trick to working on old motors is to clean everything before working on it. You got rusted studs? Wire brush them first to get that rust off. IF you have a nut to take off use heat first, then if still stuck try PB Blaster. Heat usually frees up everything. I use MAPP gass... hotter and lasts way longer than propane. You can use acetylene if you are careful.

The only special tool you will need is a valve spring compressor and most auto stores loan them for free.

I've had better luck with mixture of auto trans fluid and acetone (half and half) that Kroil or PB Blaster or WD or anything. good luck, soak quite awhile, exhaust related stuff bad to break

I've had the exact opposite experience... fluids never seem to work for me... heat, just about every time. Pro tip: let the heat soak in for about a minute (or more, depending on how thick the nut or metal is you are heating). If you heat it, then immediately try and turn it the heat hasn't worked all the way down into the part.

I'm curious, because I honestly don't know that I've ever had a stuck valve, if it's partial, will it eventually work itself loose??

'Stuck valve' is a general term. Its the valve bent? Is the guide damaged? Is there rust/debris interfering with the stem? Is the valve welded to the seat?

Could be anything... best bet it to take the time to fix it. It won't get better magically... it may work for a while, but wear is wear. Plus once the head is off you may find other issues that make the motor a keeper or junker.

Plus if it is not moving you have a rocker, push rod, tappet and cam lobe that are getting damaged as the motor rotates. If you are lucky you simply bend a push rod. Worse case? Wipe a lobe, snap a rocker, put a valve through a piston etc etc etc