valve removal

[JarrettF]

I have three stuck valves and so want to unstick them. I followed the instructions in the MM Manual until I got to step 4; then there was trouble.

I took the valve cover off. Easy.

I marked which tappets were lifting and which valves were lifting and found that all the tappets were lifting (phew!) and three of the valves were stuck in the up position despite good tappet movement.

After moving the cylinder to TDC and tapping the valve into the down position, I lifted the valve spring and washer and removed the valve keepers. (They are so tiny!)

Then I tried to lift the valve out of the out of its guide.

No dice. I tried prying it from the top, but stopped because I didn't want to scar the head. Then I tried to lever it up from the bottom using a screwdriver inserted between the gaps in the spring. I don't recommend anyone trying this; the screwdriver slipped off the bottom of the valve and drove my hand into the metal bar the engine is mounted to. Actually, it wasn't my whole hand, just the last section of my pinky finger. I'm not certain if I actually blacked out, but when I regained awareness my hand was in the ice-filled cooler and I was trying to not wet my pants.

Right now the nail is of a shade somewhere between "purple mountains majesty" and the fur of McDonald's Grimace.

(I pause here to remind you I'm a sensitive English teacher fond of British nature poetry and not a mechanic. Yet.)

Questions:

How do I get the valve out now? Did I miss a step? Is there another component that has to come out before the valve will come free?

How do I know if the valve keepers are good?

How do I know if the tappets are good? I see they are available for sale, and the perfectionist in me wants to replace all the valves, tappets, valve keepers, etc...

(pics on the boat's site, below)

[Don Moyer]

Jarrett,

You didn't miss any steps. There is nothing holding the valve in the guide after the keepers are removed except for corrosion or rust between the stem and the guide. Valve keepers are almost always reusable unless they've suffered significant water damage in the past and the small ridge around their inside diameter wears thin in the subsequent cleaning process.

In terms of removal, I have had some success in gripping the top of the valve with a pair of vise grips to rotate the valve as I'm trying to pull it. In fact, it's usually helpful to rotate the valve back and forth in an effort to work some penetrating oil between the stem and guide prior to trying to simply force the valve upward.

Valves being very hard, it's frequently possible to grip the top of the valve quite aggressively with a pair of vise grips without damaging the valve itself. However, every now and then you will have to be prepared to sacrifice a valve in the process of removing it.

Don

[JarrettF]

I got one stuck valve of three out so far, but it is definitely not easy.

Is there any reason to take out the valve guide if it does not come out with the valve? Do they need to be replaced often? When new valves are introduced?

I took a chip out of the valve when I was manhandling it, so I will be ordering a new one. Can I use the old valve guide, and valve keepers?

[Don Moyer]

Jarrett,

Being a "valve in head" or "L-head" design (sketch attached), Atomic 4's seldom need to have their valve guides replaced. They frequently wear to a clearance of .004" to .005" and then the wear stops. The guide isn't shown in this simplified sketch, but it is between the valve stem and the section
of block through which it extends.

In some cases, early model engines with oil being sprayed along the valve springs and stems have experienced a bit of oil consumption when extremely worn valve guides allowed some oil to be sucked up past the intake valve guides during the intake stroke. Late model engines eliminated this pressurized oil spray system and rely only on an oily atmosphere to flow up from the crankcase through the 4 holes in the bottom of the valve chamber. This "oil rich atmosphere" seems to provide adequate lubrication for valve stems and guides while cutting down on the amount of oil available to be drawn up through the intake valve guides.

In both engines, unless exhaust back pressure becomes quite elevated (estimated to be approximately 3 psi or more), there does not seem to be a big contribution to total blow-by caused by excessive exhaust valve guide clearances.

Lastly for your consideration, it's very, very difficult to replace valve guides unless the engine is disassembled as during a major rebuild. In fact, access problems on most boats would make it virtually impossible.

Regards,

Don

[Chip Hindes]

If there's rust on the stem, I would try polishing it off with a strip of sand paper or a wire wheel in a Dremel in order to save the guides. Heck, if the valves are toast anyway you may as well grind it off.

[JarrettF]

Well, I learned a lot getting those three stuck valves to get unstuck.

Lubrication is All.

I tapped down the valve, then turned the engine with my new socket extension crank to get the valve to move into the up position. After the valve came up I squirted some rust breaker into the valve, uh, pocket. Repeat. for. ever.

Finally the valve came free and slid out with barely a struggle.

Unfortunately, I destroyed two of the valves before I learned The Way, but I expect that once the newbies arrive I can proceed with the reassembly. The third valve cleaned up real sweet with some sandpaper (the autoshop teacher where I work suggested I use rustbreaker as a lubricant for the sandpaper and that worked out nicely).