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HD6G 344 valve spring broken

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doctorcorey View Drop Down
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Joined: 17 Jul 2011
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Topic: HD6G 344 valve spring broken
    Posted: 09 Apr 2023 at 11:15am
Well I got the loader out yesterday, and worked it for a while, and then I picked up this sudden miss, exhaust popping, and noise. Scoped it down to the number 3, and pulled the VC this morning. Broken exhaust valve spring, #3 Ouch. I suspect it was already compromised, but failed completely. I noticed that very little oil reaches the rocker shaft and valve springs. Is this normal, or do I have a sludged up line or such? My oil pressure is rock solid, even when hot and idling. Running 15w-40 Diesel oil. If anyone has valve springs they'd sell, shoot me a message. And, any advice on a method to hold the valve in place while I remove the spring. Also, I'd like to get one fuel injector (4346227) for a spare and a play toy. My engine number is 6-10376 tractor 6-10873

Edited by doctorcorey - 09 Apr 2023 at 11:21am
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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Codger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Codger Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2023 at 6:46pm
That's All Folks!
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doctorcorey View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2023 at 9:28pm
Originally posted by Codger Codger wrote:



I'll look that up, thanks. Do you have knowledge that this spring will interchange with the #4345412 listed in the HD6G manual? I hope I find some.....I inspected all the springs and at least two are broken and a couple have sacked coils, a sure sign of impending breakage.
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Codger Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2023 at 5:52am
I don't have any Allis manuals. Found that via an online search. I wouldn't replace a single broken exhaust spring myself, but would replace them all.
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doctorcorey View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2023 at 8:44am
Yes, I'm replacing all 8. Probably pull the head next winter and do a complete valve job.
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gemdozer Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2023 at 12:52pm
I should have 24 spring valves
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMiller Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2023 at 1:44pm
Corey, If Memory Serves, or IIRC, there is ONE and ONE only Rocker Arm support or retainer bolt cut down for, that is the Lube Oil Supply off the rifling that feeds the head, is possible someone assembled incorrectly.

Edited by DMiller - 10 Apr 2023 at 1:45pm
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doctorcorey View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2023 at 5:01pm
Originally posted by DMiller DMiller wrote:

Corey, If Memory Serves, or IIRC, there is ONE and ONE only Rocker Arm support or retainer bolt cut down for, that is the Lube Oil Supply off the rifling that feeds the head, is possible someone assembled incorrectly.
    This 344 has a brass elbow threaded into the head, into a tube, into another brass elbow (with a restrictor port)on the rocker shaft. I found the restrictor hole was clogged with sludge. Possibly, the spring failure made me take a look under the valve cover and discover this problem which could have damaged a lot more parts, especially rocker tip and valve stems. Ouch
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gemdozer Quote  Post ReplyReply Direct Link To This Post Posted: 14 Apr 2023 at 11:25am
I recheck this morning and found 3 injectors AKB 75S
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Post Options Post Options   Thanks (1) Thanks(1)   Quote doctorcorey Quote  Post ReplyReply Direct Link To This Post Posted: 19 Apr 2023 at 10:11pm
Just for the sake of posterity, I am posting a part number for a valve spring that will substitute for the AC 344 engine, with either single or dual intake valve springs. Maybe it will save some one else the frustrating hassle of trying to find interchange numbers for this orphan spring. I ordered #474025242 from Ag Kits. Set of eight was around $60. They match the AC manual for installed height pressure, and pressure at lift .500. I didn't have a free length spec for the original, but the new ones have about .150" longer free length than the sacked out old Allis springs. Installed height pressure and pressure-at-lift are the real only important specs. On a side note, I received the springs on FedEx less than 24 hrs. after I ordered them. Impressive! Machine runs like a sewing machine now. 
Semper Fi USMC    1958 HD6G, 1959 MF 203 loader, 1960 Case 420B Backhoe, MF 65 Tractor/Loader Diesel
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