I have a 1940s approximately farmall cub. I checked the compression in cylinders 3 and 4 and got about 25 I think. I took the valve cover off the side and thought at first everything looked ok. I then looked closer later and realized 3 of the exhaust valves are stuck open. I took the head off and have tried using pb blaster. I got them to move but I have to hammer them pretty hard to get them closed. They are FAR from closing on their own. I don t know if I should keep trying to beat them loose or just replace them. I have considered putting pistons and rings in it as well considering I have tore down this far and the fact that I don t know for sure that the rings are good. Any help as what I should do is appreciated.
- Thread starter bdoss2006
- Start date
Rodney51Cub
Member
- Location
- Southern Illinois
If they are stuck that bad , pull them out and clean them. Then see how they move.
Janicholson
Well-known Member
47was the first cub. The stuck valves can be removed easily with a flat head style spring compressor. Simple to do. twist and pull them out with PB Blaster on
the stems. Pull evenly as you twist, and don't be afraid to go back in with them. If there is rust in any cylinder, it really needs the pistons removed and bore
wear assessed to see if oversized pistons are needed in addition to rings. They are not a sleeved engine, and they are pretty easy to work on. Take images as
you go. Jim
the stems. Pull evenly as you twist, and don't be afraid to go back in with them. If there is rust in any cylinder, it really needs the pistons removed and bore
wear assessed to see if oversized pistons are needed in addition to rings. They are not a sleeved engine, and they are pretty easy to work on. Take images as
you go. Jim
old
Well-known Member
- Location
- Camdenton Missouri
If they are that bad good chance you will never free them up unless you pull them out and clean both the valve stem and guide. Last summer I picked up a Cub for $200 and just had a couple stuck valves and they did as yours are and I have to pull them and clean things up and now it run just fine
old
Well-known Member
- Location
- Camdenton Missouri
Only if you pull the oil pan and pull out each piston
old
Well-known Member
- Location
- Camdenton Missouri
If you replace the valves it is best to have a machine shop also replace/grind the seats
Steve@Advance
Well-known Member
Start soaking them with penetrating oil, hammer the stem end with a soft
hammer, but be gentle.
DO NOT hit the big end or damage it in any way!
Keep up with where they came from, and put them back in the same place.
Once cleaned up and free, lap them with lapping compound, see what the seats
look like. If they don't lap good enough to see a good seal, the head will
need to go in for machine shop work.
The only way to know about the bottom end is to take it apart and look, or
put the head back on and get it running. That is what I would do, just get it
running for now. That way you can check out the rest of the tractor, see what
else it might need.
hammer, but be gentle.
DO NOT hit the big end or damage it in any way!
Keep up with where they came from, and put them back in the same place.
Once cleaned up and free, lap them with lapping compound, see what the seats
look like. If they don't lap good enough to see a good seal, the head will
need to go in for machine shop work.
The only way to know about the bottom end is to take it apart and look, or
put the head back on and get it running. That is what I would do, just get it
running for now. That way you can check out the rest of the tractor, see what
else it might need.
grandpa Love
Well-known Member
Those valves didn't get stuck in a day,
won't free up in a day. Lol.
Penetrating oil, tap and pry, take your
time. May take several days. If you
take valves out, put them back in same
place! Get valves moving, buy a new
head gasket ( O'Reilly's) and put it
together. See how it runs. It's rare
that we have to pull the head to free
up valves, these cubs want to run.
We have bought them with stuck valves,
stuck motors, and over all a hot mess,
almost every one is back to work!
won't free up in a day. Lol.
Penetrating oil, tap and pry, take your
time. May take several days. If you
take valves out, put them back in same
place! Get valves moving, buy a new
head gasket ( O'Reilly's) and put it
together. See how it runs. It's rare
that we have to pull the head to free
up valves, these cubs want to run.
We have bought them with stuck valves,
stuck motors, and over all a hot mess,
almost every one is back to work!
used red MN
Well-known Member
- Location
- Coon Rapids, MN
Steve FYI, the part with the valve seat in it is the engine block.. flat head.
Lap them in with some valve grinding compound.You will need to get some valve lapping compound,a hand lapping dart,lap them in with some oil on the stem and compound on the face.After lapping wipe off seat and face real good and then check the face for contact ring also contact ring on the valve seat,should be narrow line about 1/2 way on the face.
I pulled 7 of the 8 valves out, one is stuck so tight I don t know if I ll ever get it out. I am considering just replacing all the valves. They are pitted pretty bad, especially on the top. I can t even get a lapping tool to stick to it, and I would be surprised if I didn t damage them getting them out. Also, while cleaning the top of the block, I noticed that the piston has a lot of movement. (I am trying to get a video and pictures uploaded) I don t know if thats normal if that means it needs new rings.
This post was edited by bdoss2006 on 09/24/2022 at 09:46 pm.
This post was edited by bdoss2006 on 09/24/2022 at 09:46 pm.
J.Wondergem
Well-known Member
- Location
- Rockford, Mi.
Sounds like it'll be best for a complete overhaul.
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