Retorquing Head Bolts

F

FarmallAddict

Well-known member
I have some seeping from the head gasket on my 1947 cub. It was completely rebuilt less than 3 years ago. I drained the oil and it looked perfect, the coolant level never changed other than the overflow tube like all early cubs, no smoke and the engine runs perfect.

Before I completely take the head of and replace the head gasket I was going to try retorquing the head bolts. They were retorqued once after an hour or two of running so they may just need to be retorqued again. The engine builder used some sealant on the bolts that go into the water jacket. The plan was to warm up the tractor to operating temperature, then take the hood off and slighty back off the head bolts before retorquing to 45 lbs just to make sure they are cracked lose before pushing them tighter. I'm a little worried about breaking them off because then it's a nightmare when that happens. New head bolts were used on installation after the head was machined.

The seeping is very minor and almost completely goes away once the engine gets to operating temp. Anything wrong with my plan? It's already seeping a little so I figure I don't have much to lose if a head bolt starts leaking. I have a new head gasket and new bolts if it comes down to completely replacing it.

Thanks.
 
I'm not an engine guy, that said, I don't understand why you would loosen head bolts prior to torquing. Seems like that would then necessitate retorquing after running the engine for a few hours. If the head bolts are new there should be little chance of snapping one off. IMO
 
I agree with Bob. I would retorque without loosening them and if that didn’t resolve the issue I would consider replacing the head gasket. If you decide to replace the head gasket be sure to check the head and block for warpage and I would recommend copper cote on the gasket before installing
 
Bob McCarty":2hirfl5d said:
I'm not an engine guy, that said, I don't understand why you would loosen head bolts prior to torquing. Seems like that would then necessitate retorquing after running the engine for a few hours. If the head bolts are new there should be little chance of snapping one off. IMO
Click to expand...

You might be right. It was a tip someone had given me. I was worried the sealant would lock the head bolts in place and give them an artificially high torque value. It's probably unnecessary and if they don't move I can just replace the whole gasket.
 
Do you know what type of sealant was used? Was it put on all head bolts whether they went into the water jacket or a dry hole? I ask this because the sealant will alter the bolt's behavior when torqueing it. You want them all to act the same.

If they all were treated the same, you can try just retorqueing them (in normal sequence). If they don't all move, at least a little, I would consider the operation to be questionable but it may work. If you want to crack each one loose before torqueing, I would loosen all then go through the full multi-step process of torqueing the head down. Do the loosening in the reverse of the torqueing sequence. Crack each one loose then bring it back to snug before loosening the next.

If the same sealant was not used on all bolts, I would complicate the loosening step to: Drain the coolant, remove, clean, put new sealant on the threads, reinstall and snug down each bolt.

I use Teflon liquid pipe thread sealant on the head bolts.
 
If I remember correctly the first re-torque was called for at 10 hours after rebuild. I would check the bolt's torque and tighten up to specs if less than specified. You definitely do not want antifreeze to get into a cylinder(s) is it could cause a localized overheating condition of the cylinder's rings, piston, or rod etc.
 
Hi,
The Cub operator's manuals from the 1940's and 1950's don't have any info about when to retorque the head bolts, that I have seen.

The 1965 Cub operator's manual says to retorque the head bolts after the first 50 hours of use, when the tractor was new.
It also says to retorque the bolts after the first 50 hours of use after installing a new head gasket.
Below is the page.

http://farmallcub.com/rudi_cub/www.clea ... age-71.jpg

Below is page 41, it says to look at on the page above.

http://farmallcub.com/rudi_cub/www.clea ... age-41.jpg

Below is a page from the Cub service manual showing the head bolt torque sequence. :)

http://www.farmallcub.info/manuals/gss- ... 001-14.jpg
 
Glen
You are one of the best. Always ready and helpful with the proper links to the neccesary information needed. Just wanted to take this opportunity to thank you for being such a valued contributor on this forum.

Hutch
 
Jim Becker":2hovqlhh said:
Do you know what type of sealant was used? Was it put on all head bolts whether they went into the water jacket or a dry hole? I ask this because the sealant will alter the bolt's behavior when torqueing it. You want them all to act the same.

If they all were treated the same, you can try just retorqueing them (in normal sequence). If they don't all move, at least a little, I would consider the operation to be questionable but it may work. If you want to crack each one loose before torqueing, I would loosen all then go through the full multi-step process of torqueing the head down. Do the loosening in the reverse of the torqueing sequence. Crack each one loose then bring it back to snug before loosening the next.

If the same sealant was not used on all bolts, I would complicate the loosening step to: Drain the coolant, remove, clean, put new sealant on the threads, reinstall and snug down each bolt.

I use Teflon liquid pipe thread sealant on the head bolts.
Click to expand...

I don't know what sealant was used. I can call the engine guy and ask.

Hopefully the weather will cooperate with me this weekend and I will give it a shot. When you use the Teflon sealant do you just lightly coat the bolt threads or the entire bolt? I've never redone the head gasket on a tractor before, just smaller aircooled engines like a snowblower and lawnmower. I do have a can of copper sealant for the gasket if it comes down to it. Head Bolts and head gaskets make me a little nervous. The block should be flat because it was machined a few years ago but you never know what could have happened up until now. If it is way off I will have some questions to ask the engine rebuilder.
 
Bob McCarty":tb071zbp said:
I'm not an engine guy, that said, I don't understand why you would loosen head bolts prior to torquing. Seems like that would then necessitate retorquing after running the engine for a few hours. If the head bolts are new there should be little chance of snapping one off. IMO
Click to expand...
Agree. As someone who spent 20 years as a line mechanic and 50+ years building hot rods and restoring antique vehicles I did many. many, many engine rebuilds and head gasket replacements and I would love to know exactly where this idea of loosening headbolts to retorque them got started. For one thing when you loosen the headbolts you are risking coolant seeping between the gasket and block or head. When you then retorque the head you can get a false reading because you are compressing the coolant. Eventually that coolant will dissipate leaving the head undertorqued. For another thing if you loosen them first and then torque them down you aren't really retorqueing them you are simply restarting the original torqueing process. The term "retorqueing" is a misnomer, the process should correctly be called "checking the torque settings" and if it's done at all it is done once, and only once, at the factory prescribed time period. After that if it looses it's setting it's generally due to a deterioration of the headbolt (stretched/corroded), or the headgasket has developed a problem. That's assuming the factory torque process was followed to the letter originally.

Be aware that using a thread sealant where the factory has not specified it will also give a false torque reading and almost guarantees the need to check the torque after x number of hours.
 
radioguy41":3lxlv9cs said:
Bob McCarty":3lxlv9cs said:
I'm not an engine guy, that said, I don't understand why you would loosen head bolts prior to torquing. Seems like that would then necessitate retorquing after running the engine for a few hours. If the head bolts are new there should be little chance of snapping one off. IMO
Click to expand...
Agree. As someone who spent 20 years as a line mechanic and 50+ years building hot rods and restoring antique vehicles I did many. many, many engine rebuilds and head gasket replacements and I would love to know exactly where this idea of loosening headbolts to retorque them got started. For one thing when you loosen the headbolts you are risking coolant seeping between the gasket and block or head. When you then retorque the head you can get a false reading because you are compressing the coolant. Eventually that coolant will dissipate leaving the head undertorqued. For another thing if you loosen them first and then torque them down you aren't really retorqueing them you are simply restarting the original torqueing process. The term "retorqueing" is a misnomer, the process should correctly be called "checking the torque settings" and if it's done at all it is done once, and only once, at the factory prescribed time period. After that if it looses it's setting it's generally due to a deterioration of the headbolt (stretched/corroded), or the headgasket has developed a problem. That's assuming the factory torque process was followed to the letter originally.

Be aware that using a thread sealant where the factory has not specified it will also give a false torque reading and almost guarantees the need to check the torque after x number of hours.
Click to expand...


I appreciate the feedback. Forgive me I'm very new to working on cub engines. It also leads me to believe the thread sealant could be responsible for a false torque value because the head isn't on as tight as the torque would indicate. It's at least one possibility with my machine. I'll have to find out if those bolts are still torqued to 45 lbs. If they don't move then I will take the head off and start over. It seems like almost everyone uses a little sealant on cub head bolts from what I've read. I'm just trying to keep mine running for another 70 years so I can pass it on to the next generation.
 
Hi,
Thank you k hutchins for the kind words. :)

Below is a post I wrote on with info about replacing a Cub head gasket.
The post is part way down the page. :) :tractor:

viewtopic.php?f=1&t=102173&p=807849

You can use the product Jim B. said above, instead of what I wrote in the post if you want.
 
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