Head Bolts

goxu1

goxu1

Well-known member
I know it’s been discussed a 1000 times , but I’d just like to know if the head bolts I bought from TM (grade 8 I believe) are up to the job?
I don’t want to get half way thru the job and end up with another broken bolt. Past threads have said grade 8 are rated at less than the required head boot torque. Do I need to get grade 9 and cut them to length , or are they available in correct sizes ?
 
They are fine. It is important to use a new gasket, use the copper gasket spray on the gasket, place the gasket the correct side up, and use thread seal on the bolts and to torque in sequence per the manual and retorque after some run time.

I think I read somewhere on this site that the dot bolts from the early cubs would be rated at or below a grade 5 by today's standards. SO a grade 8 is an upgrade. The two reasons for the torque spec on a head bolt is clamping force. The second and main reason is to stress the bolt above what it sees in the field to reduce high cycle fatigue. There are torque charts available for bolts. https://www.fastenal.com/content/feds/pdf/Torque-Tension Chart for A307 Gr5 Gr8 Gr9.pdf

Remember to use the spec for "lubricated" as the thread sealant is also a lube.
 
goxu1 said:
I know it’s been discussed a 1000 times , but I’d just like to know if the head bolts I bought from TM (grade 8 I believe) are up to the job?
I don’t want to get half way thru the job and end up with another broken bolt. Past threads have said grade 8 are rated at less than the required head boot torque. Do I need to get grade 9 and cut them to length , or are they available in correct sizes ?
Click to expand...
 
In addition to what’s been advised, I would also run a thread tap through all the holes to clean them up.
 
Google says the max torque for a 3/8 grade 8 is 58 , so the setting of 45 should be fine I guess
From the chart above , 3/8 lubricated = 33. Does the sealant make it “lubricated” ?
 
I don’t know where Dr google got its number, but the gm bolt torque tables for a grade 8 3/8 bolt is 38 ft lb. When they talk lube, think arp bolt lube, threads and under the bolt head.
When I did the ‘65 a few years back, I used grade 8, with grade 8 washers, thread sealant, light lube, no gasket spray, torqued in sequence to 40 ft-lb, no retorque after running…and it’s still running almost 10 years later.
 
As I understand it bolts that are marketed as engine head bolts are made differently than a standard application bolt. The bolt material and torque ratings, among other things, are different.
 
Ok , the more I look the more it seems to be the max torque for a 3/8-16 is 45
The torque spec for the cub head bolts is 45 too.
So , like ntrenn said, should I just go to 40 with the sealant and be on the safe side ?
 
Definitely use grade 8 bolts…..your future mechanic in 20+ years will thank you!

No one like to remove broken head bolts!

NJ Farmer
 
Hi,
Below is the bolt torque chart from the Cub and LoBoy service manual, telling what IH said about bolt torques. This chart is in their 1976 manual.
It has info about the bolt markings lower on the page. IH started using modern bolt head markings with lines on Cubs in about the mid 1950's, from what I have seen.
Before that they had just the dot in the middle of the heads.
They were putting WP on the heads in the 1970's, like the pictures show.
 
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goxu1 said:
Ok , the more I look the more it seems to be the max torque for a 3/8-16 is 45
The torque spec for the cub head bolts is 45 too.
So , like ntrenn said, should I just go to 40 with the sealant and be on the safe side ?
Click to expand...
I sent an email to Ron at TM Tractor asking if he knew the maximum torque value for the head bolts that he sells. And if he doesn't know the value, could he provide the material specs for his head bolts. His response: "my head bolts are grade 8 and can be torqued to more than the head torque for the Farmall Cub. I have used them many times with no issues". While not answering my specific question, it does support my understanding that:
  1. Head bolts are usually higher alloy compared to standard application Gr 8 bolts
  2. They achieve the grade 8 levels of yield and tensile strength without being brittle
  3. They are manufactured with a shoulder (as confirmed on TM Tractor website) and higher class threads
If you wish to reduce the torque for thread sealant applied to the head bolts, that is your decision. The primary thing you are trying to achieve with the manufacturer's recommended torque values is the clamping force. The clamping force that is provided should be the same when comparing the dry torque values with the suggested, torque values for a lubricated bolt. I will tell you that I used the TM Tractor head bolts when I rebuilt my '48 Cub engine and torqued them to 45 ft-lbs with the thread sealant. That was over twenty years ago with no detectable issues to date. Hope this gives you a little comfort going ahead with your installation.
 
Bill V in Md said:
I sent an email to Ron at TM Tractor asking if he knew the maximum torque value for the head bolts that he sells. And if he doesn't know the value, could he provide the material specs for his head bolts. His response: "my head bolts are grade 8 and can be torqued to more than the head torque for the Farmall Cub. I have used them many times with no issues". While not answering my specific question, it does support my understanding that:
  1. Head bolts are usually higher alloy compared to standard application Gr 8 bolts
  2. They achieve the grade 8 levels of yield and tensile strength without being brittle
  3. They are manufactured with a shoulder (as confirmed on TM Tractor website) and higher class threads
If you wish to reduce the torque for thread sealant applied to the head bolts, that is your decision. The primary thing you are trying to achieve with the manufacturer's recommended torque values is the clamping force. The clamping force that is provided should be the same when comparing the dry torque values with the suggested, torque values for a lubricated bolt. I will tell you that I used the TM Tractor head bolts when I rebuilt my '48 Cub engine and torqued them to 45 ft-lbs with the thread sealant. That was over twenty years ago with no detectable issues to date. Hope this gives you a little comfort going ahead with your instal
Click to expand...
Hi Bill , thanks for doing that. It gives me more confidence to know you used them with no dramas torqued to 45.
Thanks again
 
I am going to be installing a head gasket in about a month using head bolts from TM Tractor. I am just curious if you completed the job and, if you did were you able to torque the bolts to specifications with no problems. I’m not questioning the quality of the bolts, just looking for more information on your experience since I’ll be doing this for the first time and always get nervous torquing a bolt. I have a 20 year old Craftman “clicker” type of torque wrench. I’ve never broke a bolt. I guess it’s that long handle on the torque wrench that makes it feel like I’m using too much leverage.
Thanks.
 
The main thing to remember is, you need to put sealer on the bolt threads because the holes extend into the water jackets. Besides sealing the threads it will also provide lubrication to the threads as well. Lubricated threads require less applied torque. How much you'll need to reduce the torque is a bit of a guess since there's no torque chart that lists a thread sealer in its calculations. There's plenty of online torque charts showing the reduction in required torque for bolts using grease, oil or anti-seize. My guess is the torque reduction should probably be about the same as threads lubricated with oil.
I think the stories you hear about breaking bolts is due to people applying full torque to fasteners with lubricated threads which will easily exceed the tinsile strength of the bolts.
 
lyle11 said:
I am going to be installing a head gasket in about a month using head bolts from TM Tractor.
Click to expand...
Hi,
Here is info for putting the head and head gasket on, if you need it.
Below is the Cub and LoBoy service manual, it has lots of info.
I would read the engine section, section 1, before working on the engine.
There is a contents beginning on page 1 of most sections, that makes it easier to use online.
https://farmallcub.club/rudi/farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue Ribbon Service Manuals/GSS-1411 Service Manual for Cubs and Lo-boy Tractors/index.html

You didn't say the year of the Cub. This manual was made in the 1970's so it has newer, 12 volt electrical system info.
Remember to use non hardening sealer on the head bolt threads when putting the head on the engine. I use Permatex Aviation Form A Gasket, it comes in a small can with a brush under the lid.
Stir it before use, it can settle sitting. They sell it at NAPA in my area.
There is a head bolt torque sequence in the service manual, on page 1-14.
I would torque the head bolts gradually in steps, 25, 35, then 45 ft lbs. Each time following the torque sequence.
You could use copper spray on the head gasket when putting the head on, if you want.
Spray it on just as you put the head on, and put the head on while the spray is wet.
Use an even amount on both sides of the gasket. If you haven't used it before, I would practice spraying it on some flat metal first.
After putting the head on, I would let the engine sit for a day before putting coolant in it, so the sealers can dry some. Don't run the engine without coolant in it.
Below are pictures of the sealer and copper spray. :)
 

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The 1965 Cub operator's manual says to retorque the head bolts after the 1st 50 hours of use, for a new tractor, and on page 41 for a Cub engine that had the head off, and the head gasket replaced.
Or you could retorque it with less hours of use too.
The engine should be cold when torqueing the bolts.
Below is one page. :)
https://farmallcub.club/rudi/farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Cub%20Owner's%20Manuals/International%20Cub%20&%20Lo-Boy%20Operator's%20Manual%207-29-65/Page-71.jpg
 
Thanks Glen. I was mostly just curious about Paul’s experience. Just to see how it all worked out for him. I have printed out the instructions with the bolt tightening sequence. I’ll be using the copper coat and sealer you recommended.

I am in Ohio, but this is the Cub that I was working on last October in Wisconsin. I inherited 80 acres with a house and shed and grew up there, so I go there about a half dozen times between April and October. Because of limited time there, and my sister mowing when I’m away, it’s harder to deal with breakdowns. I have 2 Cubs there, a 48 FCub and a 55 Lowboy. The engine I am installing a head gasket on was manufactured in 1969 which is installed in the Lowboy.

Last November, I bought a complete Cub engine. It was already off the tractor and I didn’t hear it run, but I trust him. He is very familiar with Cubs and sells complete engines. For $300 I could hardly go wrong because other than the hydraulic pump, it came with all the parts to “plug and play” including fan and clutch/pressure plate and underslung exhaust manifold. Carb is aftermarket China made. So worst case, I hope I don’t need the complete engine but I have a lot of extra parts.

I’m waiting for it to warm up there but I plan to get there and work on the head gasket in late April.
 
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lyle11 said:
it came with all the parts to “plug and play” including fan and clutch/pressure plate and underslung exhaust manifold.
Click to expand...
Before putting the head on, you could check it and the top of the block for flatness, with a long straight edge.

Whichever fan you use, remember to oil the fan hub. The 1957 LoBoy operator's manual tells how to oil the fan hub, something often not checked, people on here have said.
They can get low if nobody checks them, then the fan bearing can wear, or the fan can seize up.
I use a pump oil can to put clean, light motor oil in the hub.
Be careful to not lose the small gasket that should be on the oil filler screw, it might be stuck on the hub. You could also check the hub for wear, or looseness. It should have no play in the bearing.
Below is the page with the fan hub lube info.
https://farmallcub.club/rudi/farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Cub Owner's Manuals/International Cub Lo-Boy Tractor Operator's Manual 9-30-57/Page 36.jpg
 
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Glen said:
Hi,
Here is info for putting the head and head gasket on, if you need it.
Below is the Cub and LoBoy service manual, it has lots of info.
I would read the engine section, section 1, before working on the engine.
There is a contents beginning on page 1 of most sections, that makes it easier to use online.
https://farmallcub.club/rudi/farmallcub.com/rudi_cub/www.cleancomputes.com/Cub/Blue Ribbon Service Manuals/GSS-1411 Service Manual for Cubs and Lo-boy Tractors/index.html

You didn't say the year of the Cub. This manual was made in the 1970's so it has newer, 12 volt electrical system info.
Remember to use non hardening sealer on the head bolt threads when putting the head on the engine. I use Permatex Aviation Form A Gasket, it comes in a small can with a brush under the lid.
Stir it before use, it can settle sitting. They sell it at NAPA in my area.
There is a head bolt torque sequence in the service manual, on page 1-14.
I would torque the head bolts gradually in steps, 25, 35, then 45 ft lbs. Each time following the torque sequence.
You could use copper spray on the head gasket when putting the head on, if you want.
Spray it on just as you put the head on, and put the head on while the spray is wet.
Use an even amount on both sides of the gasket. If you haven't used it before, I would practice spraying it on some flat metal first.
After putting the head on, I would let the engine sit for a day before putting coolant in it, so the sealers can dry some. Don't run the engine without coolant in it.
Below are pictures of the sealer and copper spray. :)
Click to expand...
Thanks Glen,

Finally got back to my place in Wisconsin and got a nice warm day today. So I followed your instructions used Copper Coat and right now I have the head installed with the threads lubricated with Permatex Aviation Form a Gasket sealer. At this point all are torqued to 35 foot pounds.

I realize there's no 100% clear answer on this stuff so I'm just looking for recommendations on torque reduction based on my scenario.

The reason I'm a little bit nervous about it is because I did have to drill out three of the broke out bolts. And now that I got it out in the sunshine, I can see that one of the retapped holes isn't a complete 360°. Two of the others that have been tapped seem fine but they feel a little rougher than those that didn't have to be touched.

So more than breaking head bolts I'm a little concerned about stripping, particularly that one where the threads don't form a complete 360. Getting to 35 pounds there were no problems at all. I felt real solid for all of them. I followed service manual and the torque pattern ramping up gradually.

Just looking online search for "torque reduction for lubricated bolts" recommended 35-45% reduction with threads lubricated with oil. Lubrication with grease or other substances weren't that much different. So right now I'm at about 22% reduction.

So my question then is:

Based on what I mentioned above, do you think I should just stop and call it good at 35 foot pounds?
I realize this is subjective, but just looking for opinions based on, especially the retapped holes that make me nervous.
Thanks
 
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