Bad compression

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ParlowMillFarm
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Bad compression

Postby ParlowMillFarm » Thu Oct 13, 2016 11:26 am

IMG_1179.JPG
dirty head
Folks,

My compression is 10, 60, 100, 95. I have pulled the head, and noticed that there was a ton of carbon deposits.

So I will take out valves to clean things up and see if I have any seating problems.

Should I keep each cyl valves separate? or can I throw them all in the same box?

Also, any special cleaning tricks for the head?

IMG_1169.JPG
head pulled off - lots of carbon


IMG_1175.JPG
close up of #1 and #2


IMG_1179.JPG
dirty head

Bob McCarty
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Re: Bad compression

Postby Bob McCarty » Thu Oct 13, 2016 12:08 pm

Mark the valves so you can replace them in the same bores. To clean the carbon, a wire wheel or fiber disk on a right angle grinder. Just make sure you blow out the dust well. Check for a ridge at the top of the cylinders which would indicate wear, you may have worn rings too.

Bob
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we need to think differently."
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LRiddle
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Re: Bad compression

Postby LRiddle » Thu Oct 13, 2016 12:12 pm

I've bever been into a cub engine, but I would keep all the valves in order so they go back the same way. What I've done before with push rods and the like is to take a piece of cardboard and put 8 holes in it for the rods or stems to fit into, mark the cardboard showing the front of the engine and number the holes. That will help keep them organized and they could sit on a shelf for awhile and you'll still be able to put them back correctly.
Luke Riddle
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ParlowMillFarm
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Posts: 157
Joined: Mon Oct 17, 2011 4:56 pm
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Tractors Owned: 1949 Cub
1964 JD1010
Location: Marion, Massachusetts

Re: Bad compression

Postby ParlowMillFarm » Thu Oct 13, 2016 12:34 pm

Thanks to both of you. I will start taking these our after I find the clamp to depress the valve springs.
John

ParlowMillFarm
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Posts: 157
Joined: Mon Oct 17, 2011 4:56 pm
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Tractors Owned: 1949 Cub
1964 JD1010
Location: Marion, Massachusetts

Re: Bad compression

Postby ParlowMillFarm » Sat Oct 15, 2016 4:48 pm

I have removed the valves, and they look pretty good, now that the carbon has been removed.

I do have some pitting on 3 of the 4 exhaust valve seats.

Valve_seat_2.jpg
#2 valve seats


Valve_seat_3.jpg
#3 Valve Seat


[Sorry for the photo quality.] Can this be fixed by just valve lapping?

Last time I had the head off someone came from a nearby machine shop with a portable valve grinder - but I can remember who it was.

Also one of the little retainer clips at the bottom of the valve spring disappeared. Can I safely assume its at the bottom of the oil pan?

Bob McCarty
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Re: Bad compression

Postby Bob McCarty » Sat Oct 15, 2016 5:12 pm

Lapping won't do much for the pitting. I think you'd want to get the seats recut while you have the head off (and probably have the valves refaced). The keeper may be in the oil pan, if not, they're easy to get.

Bob
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Re: Bad compression

Postby Eugene » Sun Oct 16, 2016 10:22 am

Compression results were, well poor. Did you do a dry then wet compression tests?

What is the history on this engine?

1949 Cub. My guess is that you will need to rebuild the engine. I wouldn't reinstall the valves and head until I knew the condition of the rest of the engine.
I have an excuse. CRS.

ParlowMillFarm
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Joined: Mon Oct 17, 2011 4:56 pm
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Re: Bad compression

Postby ParlowMillFarm » Sun Oct 16, 2016 2:19 pm

OK, I'm getting beyond my knowledge base here (I just had to read about a wet compression test) so please bear with me.

The compression results, 10-60-100-95, were from a dry test on a cold engine. Also when I removed head, the head bolts didn't seem too tight (20 years ago when I last pulled head I put the bolts back in with never-seize and can remember retorquing them).

I took the engine to a machine shop in 1980, but I really have no idea what was done to it.

Yes 10 is poor. Does it make sense to put this together to run a wet test?

Suggestions as to my next step is much appreciated.

John

Eugene
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Re: Bad compression

Postby Eugene » Sun Oct 16, 2016 2:41 pm

ParlowMillFarm wrote:Yes 10 is poor. Does it make sense to put this together to run a wet test?
I wouldn't. 1980, 36 years since last significant engine work. More than likely due for a rebuild.

I would pull the engine and put it on the bench or engine stand. But then I have all the necessary equipment.

The other alternative is to drop the oil pan, plastigage each crankshaft journal as you remove the pistons. Basically, I'm headed toward an in tractor overhaul.

Edit: You know you have some machine work due on the exhaust valve seats. I wouldn't reassemble the valves and install the head for a wet compression test. Rip the puppy apart, measure everything and determine what it's going to take to put the engine back in top condition.
I have an excuse. CRS.

ParlowMillFarm
5+ Years
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Posts: 157
Joined: Mon Oct 17, 2011 4:56 pm
Zip Code: 02738
Tractors Owned: 1949 Cub
1964 JD1010
Location: Marion, Massachusetts

Re: Bad compression

Postby ParlowMillFarm » Sun Oct 16, 2016 5:23 pm

OK. So in 1970 I had a starting problem with a 1938 Ford that belonged to my boss. I asked the #1 man in the two man operation for advice. He said, "What! ! I just rebuilt that engine."
I said "when was that."
he said 1944.
Now I know how he felt.

Thanks Eugene, even if it's bad news. I'll keep you posted.

I guess it's too early to prime the head.

ParlowMillFarm
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Posts: 157
Joined: Mon Oct 17, 2011 4:56 pm
Zip Code: 02738
Tractors Owned: 1949 Cub
1964 JD1010
Location: Marion, Massachusetts

Re: Bad compression

Postby ParlowMillFarm » Sun Oct 16, 2016 5:34 pm

Eugene!
Most likely I'll have to remove the engine and send it out due to my total lack of knowledge ( like what is a journal?) and time constraints.

How much will engine weigh - less head?

John

Eugene
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Re: Bad compression

Postby Eugene » Sun Oct 16, 2016 7:30 pm

ParlowMillFarm wrote:How much will engine weigh - less head?
Around 130 lbs without the head. Complete engine, long block weighs around 150 lbs. That's without the flywheel.
I have an excuse. CRS.

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Glen
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Re: Bad compression

Postby Glen » Sun Oct 16, 2016 8:14 pm

Hi,
Crankshaft journals are where the bearings run on the crankshaft. Each one should be a smooth surface. They should be measured to see if they are worn. If they look bad, or are worn, a shop can regrind the crankshaft so all the journals are smooth and a uniform size again, unless the crankshaft is too bad or too worn.
After regrinding, they need undersize bearings, to match how much material was removed from the journals.
Here are pics of a Cub crankshaft from TM Tractor. This is a used crankshaft, it looks like. :)
Attachments
Cub crankshaft.jpg
Cub crankshaft 3.jpg

ParlowMillFarm
5+ Years
5+ Years
Posts: 157
Joined: Mon Oct 17, 2011 4:56 pm
Zip Code: 02738
Tractors Owned: 1949 Cub
1964 JD1010
Location: Marion, Massachusetts

Re: Bad compression

Postby ParlowMillFarm » Sun Oct 16, 2016 8:40 pm

Glen and Eugene,

Thanks for the information. I'll try to find a machine shop tomorrow and scope out the logistics of engine removal that I saw in earlier posts (block the wheels!)

John

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Glen
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Re: Bad compression

Postby Glen » Mon Oct 17, 2016 8:54 pm

Hi,
If you are removing the front of the Cub, and the engine, besides blocking the wheels like you wrote above, be sure to wedge the front axle with wood wedges, so the tractor cannot tip. Drive the wedges in tight with a hammer. Check them some during the work to be sure they don't come loose and fall out. Here is a pic taken by Dale Finch.
If you remove the front of the Cub, then the wedges won't prevent the rest of the Cub from tipping, so be careful. :)
Attachments
Cub wedges 2.jpg


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