Stuck Valves /Bent Pushrods

[William Stewart]

My 1950 Chev 3100 pickup has been off the road for a few months for brake work. On trying for a restart, the engine, which usually is running after about a half turn cranking (6 Volt starter in 12 Volt system), started rough and noisey. I shut down and pulled the valve cover- two stuck intake valves and bent pushrods. Pullled the sideplate and checked for cam damage. Lifter surfaces all OK, so I'm assuming that the cam survived.

The intake valve stems have been flooded with super liquid wrench (ATF and Acetone mix) for a couple of days, but still seem solidly stuck, Any ideas short of pulling the head? The engine is a Forberg 235 rebuild with about 10K miles.

Next step? Thanks, Bill

[G&R's57GMC]

Ahh, The trouble with Ethenol in the gas may have something to do with it OR major carbon build up on the backside of the valves.

Most likely cause is leaking valve stem seals and tight valve guides.

So yes the head will have to come off.

You might want to run Z-Max in the oil when you put it back together and TOP Tier Gasoline like Union 76, Chevron or Shell use Premium it has more cleaning agents then Regular. Later use only Top Tier gasoline in whatever octane your engine likes.

Also use Techron now and then to help keep the intake system clean.

[William Stewart]

Have done a few Stovebolt valve jobs over the years, but never to free intakes stuck after sitting a couple of months. Can't comment on ethanol spiked fuel, but suspect that carbon buildup isn't a factor (intake valves, low mileage engine, clean combustion chambers and plugs). As an aircraft A&P, am familiar with Lycoming exhaust valve sticking due to carbon buildup in worn exhaust guides. Never ran into this with intakes.

Occasionally a sticking closed aircraft exhaust valve (if it sticks open the piston closes it with expensive noises) can be freed by tapping a hardwood block on the head of the stem with the rocker removed (and the piston well away from TDC).

Was hoping for something like this from the group.

Thanks, Bill (1950 3100 five window and 1978 Grumman Tiger)

[G&R's57GMC]

A friend of mine bought a '62 Falcon Ranchero from a shop that just started and moved it out of the shop in the morning and put it back in at night. So all cold operation every day for a year and a half since its rebuild. It ran great.

I drove it off the lot and got less then a mile when the #5 intake valve stuck open. I turned around went back to the shop borrowed some tools. Pulled the rockers off #5 , beat on the valves NO luck ! So valves can stick on a low milage engine.

Left the rockers and pushrods out and drove it 25 miles to my friends house on the freeway at 50 mph or so. Talk about gutless, it acted like a 3 cylinder.

Pulled the 6 cylinder engine and 2 speed auto trans and sold them . He was going to put a V8 and 3 speed auto in it.

[William Stewart]

Glen and Rita,

I get your point about low time valve sticking. Even with the head off I'll have to (re)move the valve in some way, so why not on the block? In aircraft work on old large engines, I've seen broken valve springs replaced without pulling the cylinder (piston at BDC and compressed air in thru an adapter at the sparkplug to hold the valve solidly in place) Hope not to have to pull the spring for access to the valve stem, but I can clamp a solid fixture above the stem and use a bolt to maybe jack the valve down and free.

Am still hoping that the solvent will free the valve without all this nonsense.
Maybe this is an excuse to look for a GMC 248 since the truck is straight and rust free.

Bill

[Speedbumpauto]

Why take the chance of damaging anything in/on the block since the head has to come off anyway. You can also use the air trick to remove a valve spring from an automotive engine. Sometimes with the head off you can see what caused the problem and save more parts with intelligently applied force.
If the rebuild was done with guide liners to correct guide wear, a too tight or improperly broached liner could have slipped and caused your problem. I would suspect that before the ethanol mix fuel although I have seen valves stick because of really old gas on a head that I did for a guy. Came in with stuck valves. Did a valve job and guide work and it was back in a week with stuck vavles again. Fortunately no physical damage. Pursuaded the valves out, cleaned stems, honed guides, assembled and took it back to owner. A little detective work showed the guy, who worked in a salvage yard had siphoned gas out of a couple of tanks and put in his truck. Never would have believed it if I hadn't been there. Fresh gas and the thing ran great.

[mr48chev]

I'd just pull the head and do it right and be done with it.

I don't know about ethanol but I do know from experience that running old gas that has somewhat turned to varnish will carbon up valves and stick them tight real quick. It usually happens after you drive the rig a ways and then shut it off and let it cool down. It doesn't take much old gas to do it either. The other thing as Glen said about the Falcon is that if you are in a habit of just starting the truck for a minute to hear it run and shutting it off or starting it to move it out of the way without ever letting it warm up carbon builds up around the valves pretty quick plus the moisture in there never dries out. Do that for several weeks and then let it set and the carbon gets hard and causes the valves to stick.

I'd unbolt the head and unbolt the exhaust pipe from the manifold and lift Head manifolds an all out with a cherry picker and set them on the bench as a unit and pop the valves out and clean things up and put it together with new seals and put it all back together. Remember to drain the block first so you don't get coolant down the cylinders.

[William Stewart]

OK everybody agrees that the head has to come off. Can anybody tell me how a machine shop would remove the stuck valves? Without pushing out the guides?

Bill

[Speedbumpauto]

It's all going to depend on what you see when you get the head off. It could be as simple as a few sharp raps with a hammer if the stem is up high enough to be able to grind off any mushrooming if it gets serious. You might be able to do this yourself. Remember those push rods are pretty long and spindley and they will bend without too much provocation. I'd start with a brass hammer with the head on the bench supported by a couple pieces of 2x4, rocker shaft removed and valve springs off the offending valves. I'f first try and hit the valve head and get to go back to the seated position. If it moves that will allow a little of the lube to get where it wasn't. Then hit the stem and drive the valve through the guide. If brass didn't work I'd go to steel. If that doesn't work and you don't have tooling, you have to go to the shop.

[G&R's57GMC]

I'll add to what Speedbumpauto said, Do all of the valves !

If one could stick the others may not be far behind.

[RanchTruck]

Bad gas will do this just like mr48chev said. I've had a few motors stick valves after they were got going again out of a long slumber. Once they warm up and the gum/varnish can wick up the valvestems, they seize where they were left when the engine is shut off and cools down. On a ford 361 industrial it bent a bunch of pushrods, on my subaru 1.8l, it dropped a bunch of rockers out, on my GMC 270 it dropped a pushrod out. I've since learned my lesson and now use a portable 5gallon boat tank to get things running. And to also drive them home; the last one was a motorhome with the doghouse off and the chevy 350 being fed from my trusty boat tank on the passenger floor.

You need to pull the tank and clean it out and flush the lines through with fresh gas until they come out clean.

I would try warming the valve stem up with a propane torch and seeing if you can get the gum to re-melt. Then run carb cleaner down the guide to flush it out. Just make sure to twist some wire around the top of the valve to keep it from dropping into the cylinder.

All the engines that have had the valves stick I got lucky and they un-stuck with carb cleaner. Replaced the pushrods/put them back in place, and they ran fine after on good gas from a clean tank. So I wouldn't tear the heads off just yet. It's not a normal valve guide too tight, take it to the machine shop for reaming type problem. It's lacquer set up in the guide bonding it all together like glue.

[solidaxel]

Ranch Truck, I like the heat idea!!
Don't give up.
What happens when you "tap" the valve stem with a brass hammer or hard wood, will it move any?

[William Stewart]

Thanks for the inputs. The two intakes that stuck are both closed. I can pull the head, and will do if I can't free the valves. Right now, guess I'll try a few days with carb cleaner and maybe tapping the retainer lightly to try and rock the stem back and forth to let the solvent in. If no joy, then pull the springs and try the heat suggestion. Another possibility is that angle iron fixture bolted to the head to jack the valve down (and not the valve and guide).

Would be more ready to pull the head when I locate a machine shop that handles old Chevs.

Bill

[William Stewart]

Finally was able to get back to my '50 1/2 ton Chev pickup with the stuck intake valves we discussed several moonths ago. The engine is a 235 Forberg rebuild with about 10,000 miles.

I made a fixture to push the valves toward open (pistons down) and everything now moves, but the action is sticky and too slow closing to chance running. I'm going to squirt carb cleaned on the stems and work the valves till they snap closed like the exhaust valves.

So I can check the valve travel over full lift, can anybody tell me what actual lift for intake and exhaust valves is for this engine? My shop manual dosen't say.

Thanks, Bill Stewart

[William Stewart]

Latest developments-help needed!

Got the sticking intake valves free by flooding stems with carb cleaner and using a valve depressor to get them moving freely. Set up in-cabin temporary fuel tank, filled it with new gas and was off and running. Smooth engine, around town to lumber yard for plywood etc.

This AM warming up there was a loud ping followed by rough running. Pulled the rocker cover and saw that the #6 intake rocker had broken on the pushrod side. Will check the valve for stuckness when I get the rocker shaft out but since the pushrod was OK its possible that the rocker was overstressed during the original sticking session.

I need to get a replacement rocker arm. The Shop manual says that the rocker is a LH-IN and should be marked "5". It is marked 57. The PN is given as 839463. The Engine SN is JBA36203.

Where is my best outfit to contact?

Another question: The Manual had me set the spark at 5 degrees before TDC. What is my best setting for present day gas?

Thanks for the advice already given. Bill Stewart

[solidaxel]

While you were warming up the engine, did you happen to "over rev" the engine?
With your temp gas can add about 1/2 pint of Marvel Mystery oil to it when you are running the engine.
No idea on 6 cylinder parts!

[William Stewart]

Solid-

No over revving. It was a normal start with a little choke. it ran about maybe 20 seconds at about 1000 Rpm.

Bill

[solidaxel]

I guess the bushings were just set up 'tight'., be sure to run some light oil for awhile.

You will need a lot of "break in" time on that engine before any speed runs!!!

[William Stewart]

The engine is a low mileage (less than 10k) Forberg rebuild, in the truck when I got it. Got the rocker shaft out and nothing was too tight. Believe that the rocker was hit hard when the valve decided to stick last fall. -or maybe the valve stuck again. Will find out soon. I had MMO both in the gas and a little into the carb during early running. This is the first time its let me down (including B-36 time)

Bill

[magicoolbus]

Virtually all of the comments to your thread were to remove the head and have it redone by a machine shop, yet the effort went into trying to get it running with some magic super lube. I will repeat what the others have said: Take the head off and get it rebuilt. The valves are most likely bent and no amount of lube will get them to run smoothly. The guides are most likely ruined and will need replacements. 235 heads are notorious for having cracked exhaust seats as well. Next problem with this stuck valves problem is for a valve to get stuck open, piston hits valve, valve head snaps off, piston/cylinder destroyed--This is a machinist gold mine scenario.

Try 'chevs of the 40's' for rockers. Make sure your oil passages thru the shaft tower is clear.

Good Luck. Good advice is only good if you listen to it.

[_Ogre]

doesn't sound like you want to pull the motor apart but you oviously have internal problems in the engine.
pull the head to check everything out or you might get this

[OrrieG]

You seem to be hung up on the "only 10K since rebuild". I had a 68 Ducati MC with only 250 miles on a rebuild that had an electrical fire. Every winter I was going to fix it for 30 years. Even kicking it over every few months for that time did not keep it from seizing.

Pull the head or start saving for a complete long block rebuild, its more than sticky valves.

[Old Truck Man]

Naw you dont need to pull the head. Varnish from stale gas is what most likely caused your problem. Adding outboard enging mixing oil to your fuel will help. I just unstuck two intake valves on my 83 six today. Put a nylon rope in the cyl turn the engine by hand until it locks up. you can then safely remove the valve springs. use a small popane torch to heat the valve guides while pulling & turning the vavle with a small pair of vice grips.spray & squirt the valve stem with a variety of stuff . carb cleaner oil .trans fluid ect. free them up and check after everything cools down. if you suspect the valve springs are weak replace them. Replace the seals. If the vehicle is to be sitting for a extended time run it completely out of gas. When you fire it up again start it first off a gallon jug of gas with oil mixed like you would for a chainsaw or any two cycle engine. Lots of times a engine will be started on old stale gas. its run for a time and shut off. the next time its attempted to be used the varnish that was hot when deposited on the valve stems has turned to a glue and caused the valves to stick. My neighbors H farmall tractor had the valves stick this spring because of oil stale gas. and I fixed it without pulling the Cyl head.

[Old Truck Man]

Originally Posted by RanchTruck

Bad gas will do this just like mr48chev said. I've had a few motors stick valves after they were got going again out of a long slumber. Once they warm up and the gum/varnish can wick up the valvestems, they seize where they were left when the engine is shut off and cools down. On a ford 361 industrial it bent a bunch of pushrods, on my subaru 1.8l, it dropped a bunch of rockers out, on my GMC 270 it dropped a pushrod out. I've since learned my lesson and now use a portable 5gallon boat tank to get things running. And to also drive them home; the last one was a motorhome with the doghouse off and the chevy 350 being fed from my trusty boat tank on the passenger floor.

You need to pull the tank and clean it out and flush the lines through with fresh gas until they come out clean.

I would try warming the valve stem up with a propane torch and seeing if you can get the gum to re-melt. Then run carb cleaner down the guide to flush it out. Just make sure to twist some wire around the top of the valve to keep it from dropping into the cylinder.

All the engines that have had the valves stick I got lucky and they un-stuck with carb cleaner. Replaced the pushrods/put them back in place, and they ran fine after on good gas from a clean tank. So I wouldn't tear the heads off just yet. It's not a normal valve guide too tight, take it to the machine shop for reaming type problem. It's lacquer set up in the guide bonding it all together like glue.

I agree been there done that.

[William Stewart]

Looks like there are two viewpoints on my problem. The first is to get the head to a machine shop and get rid of the sticking while also seating the valves.

The other is to free the valves with solvent and get running. Both also need to get rid of the old gas.

My situation seems that the intakes are just too gummed to trust, since my latest problem was a solidly stuck #6 after several hours of running on fresh gas. (and busted rocker)

Here's what I plan to do: Pull the head, visually inspect for cracks, remove the intakes and clean guides and stems with fine steel wool and solvent until the valves are free. Am hoping that inspecting the exhaust sealing area with the valves unseated will show no need for pulling or machine work in this area. So far the exhausts seem entirely free, but will check
.

I'm equipped to dial indicate any possible bent valves etc.

If I seem too ready to avoid work, I pulled the head of my first ('38) Chev in 1951 and they seem to have gotten heavier since then.

Will need a gasket set, etc. Any suggestions as to where to buy?

Bill