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Farmall Cub • View topic - Small bubbles around head bolt.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 4:24 pm

I can understand that with having those small bubbles coming up around the bolt head that it would indicate a compression. But with a compression leak, would I have some roughness in the way then engine runs or idles. Not thrilled about yanking the head but want it fixed the right way.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 4:45 pm

The bubbles with out it running mean that water as well as compression are leaking. The question at this point is the water leaking along the bolt threads or the head gasket. The compression leak to make it bubble is the head gasket. Now if you had the tractor out side and the water is rain or melted snow different story somewhat. Hey if you have work to do with the machine this time of year do the temp and fix it when you can. The low pressure with a an air ratchet back and forth as well as a hammer tap when it is binding will get most of the head bolts out.

As far as missing with a head gasket problem goes, maybe yes but probably no. The problem will be loss of full power. Yes a faulty head gasket could cause a miss but you don't want to go there for it would be a really bad gasket.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 5:24 pm

What is the history of this engine? Compression test results? Air bubbles in the radiator?

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 7:22 pm

Put this engine in my 49 about 5 years ago. It is out of a numbered cub, a 1976 I believe. I bought it off a cub guy in Bloomsburg Pa. He had worked the engine before I bought. Guy has had a ton of cubs and seemed to know his stuff. never did a compression test, engine always seemed to run fine. One thing though, in even warmor hot weather, it always seems to boil out a good bit of water. I know if you fill the radiator up, some will boil out til it finds it own level but this engine always through out a good bit of water. To a point that after a hour or hour and half of mowing in hot weather, I had to fill it up when I could only see steamy smoke coming out of the filler cap of radiator.

So, guess Ill pull the head. I dont have a air ratchet and wonder if a electric ratchet would work if I can find one?

See a kit online for a set of head bolts for about 95 bucks so I should go with new I guess?

NAPA head gasket ok?

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 7:32 pm

Revised my opinion. Probably head gasket leaking, might be cracked head.

Auto parts store head gasket, ok, same quality as IH store bought.

Head bolts, I wouldn't purchase a set. Wait until head removed and examine bolts. They may be satisfactory. Search this site for discussions on head bolts.

Electric impact wrench should work.

Edit: If you haven't done so, flush the engine block and lower radiator housing.

Nother edit: With the head removed you can flush the block from the top. As well as from the bottom by removing the water manifold on right side of block.
Last edited by Eugene on Sat Jan 26, 2013 7:40 pm, edited 2 times in total.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 7:36 pm

Be careful with the electric impact gun. Most dont have anyway of reducing the amount of torque that they have. The one I have has 300#s of torque
Boss

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 8:34 pm

Should I need to buy a head for my engine, are the heads from the numbered cubs the same as in the earlier cubs. I'm sure mine is a numbered cub engine as when I bought it I had to pull out the crank and have it drilled for the imput shaft bushing. Thanks

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 10:00 pm

Dan Stuckey wrote:............. But with a compression leak, would I have some roughness in the way then engine runs or idles. Not thrilled about yanking the head but want it fixed the right way.
It depends on the size of the leak, plus as the engine warms and the parts expand the leak may become less.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 10:37 pm

Dan Stuckey wrote:Should I need to buy a head for my engine, are the heads from the numbered cubs the same as in the earlier cubs.
355 691 R2 for the numbered Cubs. 355 691 R2 for the standard Cubs. How ever I don't know what the difference is.

Edit: Posting error in standard Cub's head part number, should be R1.
Last edited by Eugene on Sun Jan 27, 2013 8:23 am, edited 1 time in total.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 10:44 pm

Numbered cubs have domed pistons. Wish I had thought to ask about radiator. I know about that but just couldn't think to ask.
Two worst parts of old age, first you forget things, darned if I can remember the other.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 10:50 pm

Boiling out a lot of water = headgasket problem. Just shows you how long these engines will run even when they aren't perfect.
Head bolts - the Fastenal grade 8 bolts I put in the loboy are so far working fine. ($15+/-)
Gasket set - HS7560S is available from plenty of places - I got mine from Rockauto as I had other parts coming from them. ($20+/-)
You might consider touching up the valves and seats while you're in there. At least lap them...
Thread sealant on the bolts is a necessity - anything from loctite to pipe dope to aviation gasket sealer will work.
Heads are different between numbered cubs and regular cubs but old heads can be ground to work.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 11:25 pm

Eugene wrote:
Dan Stuckey wrote:Should I need to buy a head for my engine, are the heads from the numbered cubs the same as in the earlier cubs.
355 691 R2 for the numbered Cubs. 355 691 R2 for the standard Cubs. How ever I don't know what the difference is.

355 691 R2 for all numbered Cubs and STANDARD Cubs with engine number 312390 and above. Think Long Stripe Cubs. The head change was not related to domed pistons, which were changed in Cubs with engine number 264568. 251228 R1 is the number for the earlier head.
Last edited by bob in CT on Sun Jan 27, 2013 6:21 am, edited 2 times in total.

Re: Small bubbles around head bolt.

Sat Jan 26, 2013 11:33 pm

Here is a lengthy cylinder head discussion. I cc'd new and old heads and posted the info here. http://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=67694&hilit=cc%27d&start=30