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UPDATE: I followed Greg’s advice: mixed 1/2 transmission oil and 1/2 30W and gave a couple squirts on the valve stem with the valve open. I then barred the engine around with the crank, and started up. I heard tapping immediately (sounded like one valve)along with the dead-cylinder shake. Shut down immediately and looked: this time the keeper on Intake #1 had shifted out of place noticeably. I popped it back in place. barred the engine around a few times with the crank (primer cups relieving compression), then started up. The engine idled smoothly and no tapping. I set a slow but not dead slow idle and watched the action in the tappet chest and saw nothing unusual. After 2-3 minutes I heard the beginning of tapping again, but not as pronounced as earlier so I shut her down. Looking in the tappet chest again, I saw nothing amiss.
Next time I plan to oil each of the intake valves and bar around then allow it to sit and soak for a couple hours before trying it again.
I had an new idea: perhaps the issue is sticking intake valves. The valve begins to stick and the increase in force required to open it overloads the spring keeper causing it to shift out of place: perhaps it is worn a little, or just can only take so much. Then I realized the force does not pass through the keeper; only the valve spring force is on the keeper. Oh, well… something caused the tapping sound and the cylinder dropping out at the same time, and the keeper to be partially dislodged, and I believe it is sticking valves.
I plan to lubricate all the valves manually as Greg suggests, and let them soak a while, and see if this resolves.
I am pretty much at a loss as to what has changed to cause this issue to begin, and how to stop it. This has not been an issue since I have owned the Car, until now.
New thought: I know from past experience on industrial engines, that if the valve is partially open when compression pressure rises or combustion occurs, the pressure will push the valve closed, sometimes slam it pretty hard. I suspect that this is the event that is dislodging the keeper, because the valve stem movement could be more rapid than the valve due to inertia of the valve, removing some or enough of the spring force on the spring retainer to allow it to move out of place. Aha!
Randy and all Series 80-81 owners: I found that I would get sticking intake valves on both my 80s (including one which went to a new owner two years ago) in the spring after a period of minimal use over the winter. This usually occurred about 10-20 miles into the first spring run. The car with the better engine got stickier faster! The solution which worked for me, once the valve(s) were unstuck, was to routinely add Marvel Mystery Oil (MMO–available at Walmart) to the gas when filling at a rate of 4 oz. per 10 gallons of fuel, at least every other tankful. Once I began that regimen, I never had sticky valves again.
To expedite cleaning the deposits off your intake stems at your current point, try dribbling MMO into the carb while running the engine at 1000-1500 rpm, perhaps using a trigger-style oil can. Remove the “mushroom” but leave the cast aluminum air horn in place. Do this outside, because it will smoke like a stove filled with green wood–but may also kill mosquitos in your neighborhood.
Agree, George, and thinks for the knowledge and advice. I will pick up some MMO during lunch.
I have another question: On my Car, there is a fitting on the rear tappet chest cover, piped to a fabricated intake tube designed to hold an air filter. I wonder if this tube is passing so much air through the tappet chest that there is no oil vapor getting to the valve stems. Is this even a good idea? I suspect the engine originally had crankcase ventilation via a draft tube connected at this point, but I am not certain of this. This is a modification added before I got the responsibility of caring for this Car.
Mid-way in 1925 S80 production, the road draft tube on the timing case cover was discontinued and replaced by a tube leading from the rear valve cover to the carb air horn (see photo). A similar system was kept for later Pierces and different engines. Of course there is no PCV installed, so this is a straight vent but I don’t think the vacuum sucks any oil out of the valve chamber or starves the valve stems for lubrication.
My first Pierce, the early 1925 S80 sedan with road draft tube on the timing cover, was also subject to sticky intake valves, despite a well-worn engine.
Hi Randy. in my last message I ‘DID’ use plurals for spark plug’S’ and valve’S’..
I’m teasing ya here.. But I did intend for you to lubricate all the valves.. I’d do the exhaust valves too. No harm done, maybe some smoke from the tailpipe for a few minutes. [open the shop door, and point the exhaust out the door] You will know that all the valve stems have lubrication.
I have a theory about the keeper getting out of the spring retainer:
When the valve sticks, it is stuck open, with the spring compressed.
Then, valve abruptly gets free, and the valve, with spring and retainer slams down, hammering shut.
The long valve spring has a lot of momentum, and the spring coils keep moving down towards the spring retainer and the keeper/end of the valve stem.
With clearance between the end of the valve stem and the lifter’s adjusting bolt-head, the spring, spring retainer, keeper and valve stem act as a hammer, to stretch the valve stem. This stretching puts a lot of pressure on the ‘U’ shaped keeper, and it flexes in the retainer. so it is not ‘Stuck’ or wedged in the retainer’s keeper recess.
The stretch of the valve ‘rebounds’ HARD, pushing up on the keeper, the spring retainer and the bottom portion of the spring, Causing the lower part of the spring and the retainer to rebound UP the valve stem. This rebound movement is great enough to make room for the keeper to slide out of the retainer and out of the slot in the valve stem. Then the spring retainer catches the keeper partially out of the valve stem slot.
The result is shown in the photo at the start of this thread.
This is a theory. It would be really neat if someone had the correct photographic equipment to video a valve spring assembly go through this stick-release-rebound event.. and then play it in slow motion..
This subject is making me think i ought to pull the spark plugs and lubricate the valve stems on my ’25 S80 Touring car’s engine. It has had stuck valves in the past, but the keepers never tried to get out.. But it could happen. and it could have ugly consequences.. So it’s either direct lubrication or spray some ATF into the intake while the engine is running.. With the very real chance of fouling a spark plug or two.
Greg Long.
I know you are right, Greg: tease accepted with a smile! I was in a rush to try it, you know how that goes. At that time, only one valve had exhibited symptoms. Well, now I know. I am also comfortable my engine is not about to wreck, so I can proceed. After I get ‘er lubed up, I plan to (carefully) adjust the tappet clearance. Looks like Mr.Ev preferred 9-10 thou.
You are also right that there are some very complex and interesting dynamics going on in valve springs. I am dealing with a rash of failures of valve springs in Caterpillar 16CM34 gas engines: these are the 8000 HP units made in Germany. Usually Cat gets it right; not quite this time, apparently.
Thanks for the information, George. That appears to be an original S80 carb in your photo; my Car has a period-looking but non-original retrofit. I have thought about obtaining an original, but I have been advised maybe that is not such a good idea. My Car does start easily and run well enough as-is.
Update: to report on this morning’s activity. I used MMO underbeach open intake andvexhaust valve, a couple if good squirts with my oil can with flex gooseneck. I roller Her back to the garage door and a good thing, too: she fired right up smd poured smoke out., as expected. No sign of any sticking. I shot MMO through each spring, onto the valve stem, hoping that the intakes would vacuum some into the guide, and also because plenty of oil just feels right! She idled about ten mins with no problems. I am going to button her up and take a drive later today. I think I have her ready to go and it’s thanks to my PAS friends like Greg and George, and others of course!
Think I will try the balve adjustment and see if I can get these closer to right. Greg what was the correct clearance you suggested to me before?
I believe the factory clearance in the owner/operator manual is stated as “not less than .003”. It also states that this clearance is with the engine hot, not running, and cranked by hand.
I usually set the intakes at .004″ and the exhausts at .006″ cold. I have asked several guys in the antique engine rebuilding industry regarding the small clearances in the operators manual. I was told that the cast iron cylinder block expands more than the valves expand so the clearances will only increase as the engine gets warmer.
Randy: look closely at the head of the adjusting bolt, where the valve stem contacts the bolt. Since your engine has low miles since the engine was rebuilt, I would assume that the head of the adjusting bolt was faced off on a surface grinder. But if they were not refaced, there might be a depression where the valve stem has been hitting the bolt head. This makes getting an accurate clearance with a flat feeler gauge very difficult..
So take a close look, so you won’t be frustrated with an odd ‘feel’ from the feeler gauge.
Remember: you must make every effort to not put any rotational pressure on the lifter body, when loosening the lock nut on the adjusting bolt.
Greg Long
Thanks, Greg. I looked in the “Wiring Diagrams And Tune-Up Guide†and found 0.005†intake and 0.006†exhaust, which seems reasonable, so I went with it. I hear you about keeping force off the lifter bracket, as I reread all the relevant info I could find in the Forum (your explanation was great and you had cautioned me about this risk in person).
It was quite fiddly to get anywhere near the desired setting but you have done this so you know. My car’s clearances were wide: most were at least 0.010â€. I got them as close as possible on a first pass, then started up and let her run at idle about 10 mins. She sure sounder a lot better with the clearances reduced. I shut down and started checking again; found a couple closer than desired so I reset them. I gave out so I retired for the day. I will keep tweeking until I am confident none are too close. Having the flats ground would sure make this job a lot easier!
I figured out a way to explain and reinforce my ‘theory’ about the valve spring keeper getting halfway out of the retainer.
if you take a hammer, and hit a solid chunk of steel you will get a substantial rebound or bounce of the hammer.
I took a 16oz ball peen hammer and whacked my anvil reasonably hard, the hammer rebounded a good 6-8″. So the idea of having the valve slam shut after being stuck in the open position, is not ‘far-fetched’ at all.
Greg Long.