Valve tappets

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
Post Reply
Scott in NM
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 429
Joined: Sun Sep 28, 2003 8:04 pm
Location: Tijeras, NM
Contact:

Valve tappets

Post by Scott in NM » Tue Nov 16, 2021 7:14 am

Apparently when my L134 engine was professionally rebuilt they did not adjust valve timing. This was readily apparent as one of my valve tappet adjusting screws uses a different size wrench than the other seven, plus it is loose and doesn't hold proper valve timing. It needs to be replaced with the proper one. (A sad commentary on the skills and attention to detail of "professionals".) So can one of these be replaced by accessing through the valve cover rather than removing the head? I imagine that the valve spring would need to be compressed If there are any other tips you guys care to pass on I'm all ears.

Scott


parker007
G-Colonel
G-Colonel
Posts: 1204
Joined: Fri Oct 18, 2019 4:35 pm
Location: california

Re: Valve tappets

Post by parker007 » Tue Nov 16, 2021 7:23 am

Scott, The only way to change is to pull camshaft out. So you need to pull oil pump, timing cover, timing gears, oil pan, back off lifter adjustment, pull cam out then the lifter come out bottom.

User avatar
W. Winget
LTC, U.S. Army
LTC, U.S. Army
Posts: 4445
Joined: Mon Dec 16, 2002 10:37 am
Location: USA, Virginia, Carrollton
Contact:

Re: Valve tappets

Post by W. Winget » Tue Nov 16, 2021 10:21 am

If it's just a matter of keeping the (Incorrect) lock nut tight, you could bugger up the threads by moving the adjustment nut down, then striking the threads twice with a ... :shock: chisel :o in effect making it difficult to adjust (and also get out of adjustment :D )
Cleaning it well with a shot of carb cleaner and then some high temp locktite as well might do the job (even if you dinged up the threads as well).

Then when you have had some fun with it (years) and you decide it's time to chase another gremlin, you can pull the cam and drop that lifter/adjuster for the correct one.

Just a thought or two.
V/R W. Winget

Voltaire: “The best is the enemy of the good.”
Confucius: “Better a diamond with a flaw than a pebble without.”
Shakespeare: “Striving to better, oft we mar what's well.”
Looking for 1918 Standard B 'Liberty' truck parts

Scott in NM
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 429
Joined: Sun Sep 28, 2003 8:04 pm
Location: Tijeras, NM
Contact:

Re: Valve tappets

Post by Scott in NM » Tue Nov 16, 2021 2:37 pm

Hoo boy, I don't like either answer! Pulling everything apart is ugly, especially now that I've chased away the timing gremlins. Marring the threads is not an option, this beast deserves things to be done correctly, not bubba'ed (no sleight intended, it IS a valid option). The Loctite sounds like it could work but I want it done correctly, not just done.

So, What If? The 1804 says when rebuilding to insert the adjustment screw 3/4 of the way into the tappet How far is this actually? Can the valve spring be compressed enough to unscrew the screw and remove it, then insert the proper one? Doesn't sound like it per the responses but I still feel the need to ask as I really don't want to see things torn apart.

It appears that the obvious must occur - I take it back to the shop and say "Fix it". Darn near a rebuild at that point but they were paid to do it right and apparently did not. Not fond of this one either, it could sit in their shop for months. And then it's back to square one for the timing now that I have that perfect after five months. Then again, they may find and fix the small oil leak it has had since the rebuild and I've not been able to find.

Stay tuned, this could get interesting.

Scott

User avatar
W. Winget
LTC, U.S. Army
LTC, U.S. Army
Posts: 4445
Joined: Mon Dec 16, 2002 10:37 am
Location: USA, Virginia, Carrollton
Contact:

Re: Valve tappets

Post by W. Winget » Tue Nov 16, 2021 3:55 pm

Might
MIGHT be able to put some string/rope into the cylinder head through the sparkplug hole, enough to keep the valve in the closed position, compress the spring remove the keepers then the spring, then remove the rope/string, raise the valve up for clearance, unscrew the top adjuster off and exchange it, but the tappet has a larger base than the body so it won't come out from the top.
Just another thought
V/R W Winget
Looking for 1918 Standard B 'Liberty' truck parts

Ron D
G-Major
G-Major
Posts: 921
Joined: Thu Aug 07, 2014 9:19 am
Location: Dorchester County SC

Re: Valve tappets

Post by Ron D » Tue Nov 16, 2021 6:27 pm

Good luck dealing with your "professionals".
I think you're going to need it.
Ron D
1951 M38
1951 M100

Scott in NM
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 429
Joined: Sun Sep 28, 2003 8:04 pm
Location: Tijeras, NM
Contact:

Re: Valve tappets

Post by Scott in NM » Tue Nov 16, 2021 8:27 pm

Upon further review of the 1804 and a few glasses of wine, got to thinking. When rebuilding, the tappets and valve adjusting screws are installed, then the valves are installed. So what is the reason I can't pull the head, remove the appropriate valve, remove and replace the offending screw, then reinstall valve and head? I can't see any reason why not, so hopefully one of you folks with more experience can tell me where my logic is faulty.

Scott

parker007
G-Colonel
G-Colonel
Posts: 1204
Joined: Fri Oct 18, 2019 4:35 pm
Location: california

Re: Valve tappets

Post by parker007 » Tue Nov 16, 2021 8:43 pm

yes the screw can be removed just by lifting valve. but is your problem the screw or lifter? if you good with fingers you can compress spring pull keeper, remove spring raise valve and unscrew adjuster

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6876
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Valve tappets

Post by Wolfman » Wed Nov 17, 2021 5:43 am

Thinking on line.
I am thinking an L-134 had two types of lifters. Mostly, the interference fit adjusting screw type. No lock nut. The adjusting screw is a tight fit in the body.
The other had an adjusting screw with a lock nut to lock the screw in place.
????? Am I close ??
Most common was the interference fit type.
Back to your problem. One screw has a different size head ??? Maybe it is the type that needs a lock nut ??
Although, I have seen the interference fit type get loose. Won't stay in adjustment.
To replace just the adjusting screw, First you have to have a replacement. You would have to remove the head. Remove the valve spring and spring retainer and valve for the offending lifter. Stuff something into the lifter galley drain holes so when you drop the keepers, very possible, they don't end up in the oil pan.
With all these parts removed, you might have enough room between the adjusting screw head and valve guide to screw out the old adjusting screw with the lifter in the full down position.
Alternative. Disassemble the engine to remove the cam. No small thing !!
With the engine in the upright position, all the springs and valves would have to be removed and all the lifters be held completely up to get the camshaft out. Again, not easy. Some type of spring clamp on each lifter body. Maybe a spring type clothes pin.
The person that put the lifter in should have caught this. Taking the engine back to them may not be much more work if you end up pulling the cam.
Decisions, Decisions.
Let us know.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

Scott in NM
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 429
Joined: Sun Sep 28, 2003 8:04 pm
Location: Tijeras, NM
Contact:

Re: Valve tappets

Post by Scott in NM » Wed Nov 17, 2021 1:09 pm

OK, definitive answer, you CAN pull the adjusting screw out without taking the engine apart.

Had spare M38 engine in garage. Took off head as my ersatz valve stem compressor (two large C clamps) would not fit over the head and into the valve compartment. Compressed #2 spring and pulled out the forward screw without any problem. Just for fun, I wanted to pull the rear one from #2 also. This also worked. From what I can tell, with a proper spring compressor the head would NOT need to be removed. A relatively simple fix. Jeep goes to a local garage that has been helping with stuff like this so I'll take the two pulled screws (always good to have a spare) and we should be able to R&R the defective one.

I couldn't tell how the spring retainer lock fits at the end of the valve, or how it interacts with the valve cap. Anyone care to shed some light on this?

As an aside, my spare engine had a brass plate indicating it was rebuilt in 12/54. Didn't know there was such a placard.

Scott

User avatar
dpcd67
G-General
G-General
Posts: 11806
Joined: Mon Jul 25, 2011 3:41 pm
Location: Iowa

Re: Valve tappets

Post by dpcd67 » Wed Nov 17, 2021 6:05 pm

How do you know if it is the screw or the tappet with bad threads? You need to get a proper flathead valve compressor tool. They are easy to get.
How to assemble M38 valves is in the TM. However, I often use WW2/CJ valves instead of the special ones used on the M38 with the lash caps. Much simpler, and easy to get.
You also need to find another engine rebuilder.
U. S. Army 28 years.
Armor Branch

Wolfman
G-Lieutenant General
G-Lieutenant General
Posts: 6876
Joined: Sat Jan 12, 2008 5:25 am
Location: Tipton,In.

Re: Valve tappets

Post by Wolfman » Thu Nov 18, 2021 4:51 am

If I am reading this right, you want to know how the valve stem and spring retainer cap are fastened together ??
There is a groove in the valve stem, just above the end of the stem.
The hole inside of the spring retainer cap, the valve stem goes through, is a tapered hole. Larger end away from the spring. Smaller end toward the spring.
There are two " Keepers'. Round tapered wedge pieces that are split in half that fit on the valve stem. A rib on the inside of the keeper fits into the groove in the valve stem.
The spring and retainer cap are installed over the valve guide. The valve is placed into the guide. The spring and retainer is compressed with a spring compressor so the groove in the end of the valve stem is visible. The two" Keepers" are placed in the groove on the valve stem, large end toward the valve stem end. A little grease on the keepers will help hold them in place. The valve spring and retainer cap are released so the spring retainer cap slides carefully down over the tapered keepers, trapping them between the retainer cap and valve stem. Valve spring pressure holds it all together.
When finished, check to be sure the keepers are properly in place. Sometimes the keeper will slip out of the groove and the fit is incorrect. This is bad ! All these parts should be tightly fit together in place.
The answer you were looking for ??
When the spring is compressed for disassembly, the two keepers may fall off the stem. They are easy to lose. And if the oil drain holes in the spring galley are not plugged with something, like a piece of paper shop towel, could end up in the oil pan.
Interesting intel that you were able to get the adjusting screw out with out disassembling the spring, retainer and keepers and removing the valve.
Mike Wolford
CJ-2A
VEP GPW
Comm./Inst. SEL
AOPA ( 50 yrs)
EAA ( 49 yrs)
4th Inf. Div. - 5th Inf. Div. - 2nd Armor Div. - CIB

Scott in NM
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 429
Joined: Sun Sep 28, 2003 8:04 pm
Location: Tijeras, NM
Contact:

Re: Valve tappets

Post by Scott in NM » Sat Nov 20, 2021 6:11 pm

Valve adjustment screw replaced. I misspoke earlier, it CANNOT be taken out unless the head is removed along with the offending valve. Don't know why it worked on my test engine but in real life the valve cannot be raised enough to remove the screw, it is about two threads short. But removing the head is much better than going through the bottom!

Thanks for the inputs. Engine now doesn't purr, it hums. A sweet, melodious sound after six months of issues. Now it's just a clutch issue to harness all the engine power and we'll be all set.

Scott


Post Reply

Return to “M38 Technical Knowledge Base”

Who is online

Users browsing this forum: No registered users and 37 guests