8N head bolts

What is the correct size and length for head bolts for a 1948 8N? Grade 8 ok? Should I use a washer?

Bought the motor in pieces and head was off. I do not have the old ones to go by. Thanks.

The OEM bolt was 7/16-14 x 2 3/8 grade 8. Good luck finding that size bolt in 2 3/8". So, replace the OEM bolts with 7/16" -14x2&1/2" yellow zinc finish SAE j429 grade 8 Hex Cap screws Part # 0115163 from Fastenal for $0.89 each. Use flat washers 7/16" yellow zinc finish SAE thru-hardened from Fastenal Part # 1133816 for $0.19 each.

The block doesn't have blind holes, so make sure all the holes are open. What most folks think are 'blind holes' are really holes clogged w/ rust.

Lastly......

Torque the bolts in 3 steps, as per the manual: 20-40-65. Then, after the engine has been run to operating temp, let it cool & then re-torque them.
75 Tips

(quoted from post at 05:23:35 05/21/17) The OEM bolt was 7/16-14 x 2 3/8 grade 8. Good luck finding that size bolt in 2 3/8". So, replace the OEM bolts with 7/16" -14x2&1/2" yellow zinc finish SAE j429 grade 8 Hex Cap screws Part # 0115163 from Fastenal for $0.89 each. Use flat washers 7/16" yellow zinc finish SAE thru-hardened from Fastenal Part # 1133816 for $0.19 each.

The block doesn't have blind holes, so make sure all the holes are open. What most folks think are 'blind holes' are really holes clogged w/ rust.

Lastly......

Torque the bolts in 3 steps, as per the manual: 20-40-65. Then, after the engine has been run to operating temp, let it cool & then re-torque them.
75 Tips

Click to expand...

Thank you Bruce, exactly what I needed to know.

You're welcome. Glad to help.
75 Tips

Bruce has you covered on the bolts .

I would dry fit , without the head , any bolts that look like they may bottom out and measure the distance compared to the head thickness . Around the exhaust ports are prone to clogging up . It is a lot easier to correct a problem before you install the head . You may also keep from cracking the block and having bigger problems .

The Ford N-Series Tractor used studs w/nuts on the cylinder head from '39 up thru the 8N in 1949 and then at s/n 8N-158162 changed to bolts. Are you sure you have hex bolts? The July 1947 MPC shows two different stud lengths for 15 and three longer ones as well. Total is 18 but you need the July 1947 MPC to see which goes where. Parts catalog shows p/n 18-6066 stud -7/16"-14 & 7/16"-20 x 2.78" for the 18; and p/n 40-6066 Stud -7/16"14 x 7/16"-20 x 2.90" for the 3. STUDS use a course thread on one end and a fine thread on the other and it is important which is which. Course threads always screw into cast iron and the fine thread always accepts the fastener (nut). Eighteen 7/16-20 nuts required. No washer was used. Now, after s/n 8N-158162, Ford went to 18 head bolts, all p/n 8N-6065-A, 7/16-14" x 1-3/8" with no washer used.

Now, as Bruce says, you can just use head bolts/cap screws if that's what you prefer, as many fellas switch out when doing a rebuild. BE AWARE that the torque specs differ -every THREAD pitch size is different, and for different materials as well. A 7/16-14 thread for steel requires 65/70 ft/lb torque where as the 7/16-20 thread size requires 50/55 ft/lbs for the steel fastener. Thus, when using head BOLTS/CAP SCREWS, you will torque at 70 ft/lbs max as the 18 holes in the block are tapped for 14 TPI (Threads Per Inch). IF you have STUDS using a 7/16-20 NUT as the fastener, the torque value then becomes 55 ft/lbs max.

9N, 2N, AND 8N HEAD TORQUE SEQUENCE:

Now, the proper method of torqueing any fastener is done in three steps. At the initial assembly, take the final torque value and divide by three. You will then torque the nuts or bolts at the low setting and according to the sequence described/shown in picture above. Next, reset the torque wrench to the next setting and repeat the sequence. The final sequence is with the wrench setting at the recommended value. All procedures are done in sequence to manual specs. Once engine ahs been put through warm up procedures, let cool down and re-torque at final setting in proper sequence. You can re-torque the head now and then maybe once or twice a year if you like. This was how I was taught by an old Ford Tractor mechanic. Engine must get up to operating temperature, then shut down and let to cool down completely before re-torqing. Also, torque wrenches are meant to tighten only, never use to loosen as this will damage the internal gearing and give false readings. This was explained to me by an Armstrong tech/engineer years ago. Finally, I just wanted to add some fellas use metal head gaskets, some have head leaks so use two, but the plain paper single paper head gasket will work fine and put a dab of engine oil(That's what they used originally) on each thread. Some here may prefer the modern Anti-Seize stuff but any lubricant will affect torque values somewhat. Washers are not needed either with bolts or studs, didn't come with any originally.

Hope this helps?
Tim *PloughNman* Daley(MI)

Wow, thank you Tim and Ken. That's a lot to take in. This is an 8N engine and the serial number from I can tell is 8N 1023?6 (it's hard to read) so I am betting it had studs originally.

I think for simplicity I will just get the bolts that Bruce suggested and will go 20-45-65 in the order Tim suggested, correct?

Grade 5 is fine. No washers are required -didn't have any when new. The following chart is in the left hand side of the HOME page here under "Research & Info" --- click on LINK below



-Tim
TORQUE VALUES

If using 7/16-20 hex nuts, I'd use Grade 5 and torque at 53 ft/lbs. If using 7/16-14 hex bolts/cap screws, I'd use Grade 7 or 8 and torque at 70 ft/lbs...block thread holes must be free of debris, old grease and oil. You can chase threads with a tap but use caution. Best to get block boiled out but if not doing a complete rebuild/tear down, isn't possible. Use your compressed air, blow out holes good. Test each hole with a bolt to ensure there' s no interference with a boogered up thread, and know that the block holes are threaded at 7/16-14 NC. It's only when using studs that the hex nut use d is 7/16-20...

Tell us how it works out when done...

-Tim

Thanks again. I will let you know how it turns out.

(quoted from post at 03:49:57 05/23/17)
Thanks again. I will let you know how it turns out.

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If you use the bolt length I suggested, you will need washers because they are 1/8" longer than the OEM bolts.

Copy that...I'd get full length threads too, not shoulder style bolts, to ensure they don't bottom out at the top of threads and booger up the first few threads. I take the time and grind down new bolts to whatever length they were originally. Take a nut, screw it onto the bolt, grind down the end on a pedestal or bench grinder, until the desired length is reached, then rotate it around applying a 45? bevel on the end. Once bolt is cooled, take the nut and unscrew it off the bolt. Try the nut on and off a few times; this method ensures any remaining burr on the bolt end is removed and it will give good clean threads to use.

-TPD

(quoted from post at 08:51:53 05/23/17) Copy that...I'd get full length threads too, not shoulder style bolts, to ensure they don't bottom out at the top of threads and booger up the first few threads.

-TPD

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I'd think long and hard about that.

A bag of 10 partially threaded 7/16-14 x 2.5" grade 8 bolts from McMaster is $8.34. [b:cb4b3c7181][u:cb4b3c7181]One[/u:cb4b3c7181][/b:cb4b3c7181] fully threaded bolt is $10.80. Minimum thread length on the partially threaded bolts is 1-1/8" and there is ZERO danger of them bottoming out in the block.

Head size on a standard cap screw is a bit smaller than the OEM bolts so in addition to shortening the shank length the flat washers help distribute the load a bit more in line with the OEM head size. You could think of them as flanged cap screws if you like ;-)

TOH