Retorquing Head Bolts

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FarmerCPA
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Retorquing Head Bolts

Postby FarmerCPA » Wed May 13, 2020 3:20 pm

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.

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Re: Retorquing Head Bolts

Postby Rick Spivey » Wed May 13, 2020 4:14 pm

I'd give it a try. Like you said, very little to lose.
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Re: Retorquing Head Bolts

Postby Bob McCarty » Wed May 13, 2020 4:47 pm

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
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Re: Retorquing Head Bolts

Postby Mht » Wed May 13, 2020 5:44 pm

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

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Re: Retorquing Head Bolts

Postby FarmerCPA » Wed May 13, 2020 6:41 pm

Bob McCarty wrote: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


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.

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Re: Retorquing Head Bolts

Postby Jim Becker » Wed May 13, 2020 8:55 pm

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.

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Re: Retorquing Head Bolts

Postby DRaymond » Wed May 13, 2020 9:33 pm

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.
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Re: Retorquing Head Bolts

Postby Glen » Wed May 13, 2020 11:34 pm

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

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Re: Retorquing Head Bolts

Postby k hutchins » Thu May 14, 2020 4:51 am

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.

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Re: Retorquing Head Bolts

Postby FarmerCPA » Thu May 14, 2020 2:04 pm

Jim Becker wrote: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.


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.

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Re: Retorquing Head Bolts

Postby radioguy41 » Thu May 14, 2020 4:01 pm

Bob McCarty wrote: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

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.
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Re: Retorquing Head Bolts

Postby FarmerCPA » Thu May 14, 2020 4:32 pm

radioguy41 wrote:
Bob McCarty wrote: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

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.



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.

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Re: Retorquing Head Bolts

Postby Glen » Thu May 14, 2020 5:12 pm

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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