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Old 02-12-2021, 12:07 PM   #1
alexiskai
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Default New video: Larry Brumfield's block thread test

About a month ago I made a short video showing my take on Larry Brumfield's procedure for testing the strength of engine block stud threads. This procedure is posted on fordgarage.com, but it's pretty high-level and leaves room for interpretation. So I took some liberties with the protocol for convenience.

I subsequently heard from Larry, who is alive and well, though no longer participating on FordBarn. He was, I should mention, very nice. Over a couple dozen emails, he explained the entire procedure and his reasons for doing it that way.

So I have now re-shot the entire video to faithfully (I hope) reproduce the Brumfield block thread test. I've also included some of the research I did on my own to figure out the science behind the choices, in case anyone is interested.

Link: https://youtu.be/ibaPf0FQnZM

In the end, I probably agree about 95% with the test protocol. I still think it would be better to torque the nut up in steps as would be done in the real cylinder head install. But I promised Larry that in this video I would stick to his version of the test.

I will say, in the process of researching and shooting this video I sure learned a lot about fasteners.
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Old 02-12-2021, 03:02 PM   #2
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Default Re: New video: Larry Brumfield's block thread test

Larry is Very knowledgeable on Heads and installation process! I have followed his recommendations on all head work and Never had a problem!
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Old 02-12-2021, 05:01 PM   #3
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Default Re: New video: Larry Brumfield's block thread test

Great, informative video. Thanks.
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Old 02-12-2021, 08:44 PM   #4
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Default Re: New video: Larry Brumfield's block thread test

I have some questions.
1- Why did you use that particular thread lube?
2- Why did you use stainless steel for the spacer block?
3- Why did you use plated standard grade 8 nuts instead of hard high nuts like Larry does?
4- Why did you NOT use a hard heavy machine washer under the nut?
5- Why did you use that torque value for testing?
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Old 02-12-2021, 10:23 PM   #5
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Default Re: New video: Larry Brumfield's block thread test

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I have some questions.
1- Why did you use that particular thread lube?
2- Why did you use stainless steel for the spacer block?
3- Why did you use plated standard grade 8 nuts instead of hard high nuts like Larry does?
4- Why did you NOT use a hard heavy machine washer under the nut?
5- Why did you use that torque value for testing?
  1. I used motor oil, that's pretty standard as a thread lube for this application.
  2. Stainless steel won’t compress as easily as mild steel. 303/304 isn't the hardest of stainless alloys, but it was what was available.
  3. The Model A nuts from Mike's/Snyder's are still a high nut as compared to a regular hex nut. The original Ford nut spec is .440” high. These nuts are .437", but I felt like that was close enough. A higher nut would be better for testing to really high torque values, but that wasn't what this test was doing. Keep in mind, tests have shown that once you get beyond 7 threads, additional threads are carrying very little of the clamp load. Cadmium plating has an almost identical coefficient of friction as plain finish (0.19 vs 0.20).
  4. The hard machine washer under the nut is a good idea if you can find one hard enough. But it would also have to be a close fit around the stud to eliminate the eccentric loading problem. Bottom line, I didn't think most people trying to reproduce the test would be able to reliably source a correct washer. And in the real head application there usually aren't washers.
  5. 65 ft-lbs is the way the test is described on fordgarage.com and it's the spec recommended for the Super Brumfield heads. You should test to the clamp load you expect to use on your head. If you're doing a stock head on a clean deck, 55 would be fine.
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Old 02-12-2021, 10:39 PM   #6
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Default Re: New video: Larry Brumfield's block thread test

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Originally Posted by alexiskai View Post
  1. I used motor oil, that's pretty standard as a thread lube for this application.
  2. Stainless steel won’t compress as easily as mild steel. 303/304 isn't the hardest of stainless alloys, but it was what was available.
  3. The Model A nuts from Mike's/Snyder's are still a high nut as compared to a regular hex nut. The original Ford nut spec is .440” high. These nuts are .437", but I felt like that was close enough. A higher nut would be better for testing to really high torque values, but that wasn't what this test was doing. Keep in mind, tests have shown that once you get beyond 7 threads, additional threads are carrying very little of the clamp load. Cadmium plating has an almost identical coefficient of friction as plain finish (0.19 vs 0.20).
  4. The hard machine washer under the nut is a good idea if you can find one hard enough. But it would also have to be a close fit around the stud to eliminate the eccentric loading problem. Bottom line, I didn't think most people trying to reproduce the test would be able to reliably source a correct washer. And in the real head application there usually aren't washers.
  5. 65 ft-lbs is the way the test is described on fordgarage.com and it's the spec recommended for the Super Brumfield heads. You should test to the clamp load you expect to use on your head. If you're doing a stock head on a clean deck, 55 would be fine.
Ok.
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Old 02-12-2021, 11:02 PM   #7
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Default Re: New video: Larry Brumfield's block thread test

My question posed is what stretch or deformation does the coarse thread experience in the cylinder block? Since to my knowledge most studs use rolled threads and in most of the thread engagement is based on 75%, what effect does this point produce. If you were to check with the correct tap drill size diameter in the cylinder block holes, what oversize say .005 or .010 would be acceptable and still get good stud allowable stretch?
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Old 02-12-2021, 11:18 PM   #8
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Default Re: New video: Larry Brumfield's block thread test

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My question posed is what stretch or deformation does the coarse thread experience in the cylinder block? Since to my knowledge most studs use rolled threads and in most of the thread engagement is based on 75%, what effect does this point produce. If you were to check with the correct tap drill size diameter in the cylinder block holes, what oversize say .005 or .010 would be acceptable and still get good stud allowable stretch?
It's a complex issue and I'm not sure there's a definitive answer. Taking the second part of your question first, it's widely believed that the thread fit of the studs you get from vendors today is not the thread fit you would have gotten with the original studs. Today's studs are almost all a Class 2 fit, but I've seen reports from folks who tested NOS studs that those felt like a Class 3 fit – a very tight fit between the stud threads and the block threads. This would have the effect of increasing the effective area of engagement.

For the studs, this reduced engagement may not matter much, because we're using stronger alloys than the factory studs. However, the cast iron engine block is the same as it was 90 years ago, and in fact probably substantially worn. So over time, you're putting more and more psi on less and less internal thread. That's why the testing is important.

Regarding the issue of how much the coarse threads deform in the block under load, my understanding is that, because these are Grade 8 studs, a clamp load of 8-10k lbs is well within the stud's elastic deformation range. In other words, when the tension is removed, the stud will return to its unstressed shape and unstressed thread pitch.

However, one might also ask whether the same is true of the internal threads in the block – are they still within their elastic deformation range, after 90 years? We really don't know. It is certainly possible that these blocks all have a "countdown" of the number of times they can be fully torqued down before one or more threads fail. I worry about that – about whether the testing is shortening the useful life of the block.
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Old 02-13-2021, 07:45 AM   #9
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Default Re: New video: Larry Brumfield's block thread test

What is the advisability of using helical coil inserts?
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Old 02-13-2021, 07:50 AM   #10
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Default Re: New video: Larry Brumfield's block thread test

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What is the advisability of using helical coil inserts?
The main difficulty with thread-repair inserts is that they have to be installed carefully and correctly to ensure that the axis of the insert is precisely aligned with the axis of the original bore. Otherwise, they're great. Here's a really helpful article that explains your options for thread-repair inserts.
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Old 02-13-2021, 09:37 AM   #11
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Default Re: New video: Larry Brumfield's block thread test

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Thanks for posting. I enjoyed that video.


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Old 02-13-2021, 09:59 AM   #12
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Default Re: New video: Larry Brumfield's block thread test

Good job Colin.
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Old 02-13-2021, 11:05 AM   #13
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Default Re: New video: Larry Brumfield's block thread test

Thanks everyone. I’m still planning to make the cylinder head installation video I posted about a couple months ago. Both this video and the stud hole cleaning video spun out of that project as I realized they were too long and complicated to be part of a larger video. I’m also splitting off a separate video that’s just about the preflight checklist for a cylinder head installation.
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Old 02-13-2021, 01:15 PM   #14
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Default Re: New video: Larry Brumfield's block thread test

A very precise and well communicated video. Exceptional!
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Old 02-15-2021, 02:52 PM   #15
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Default Re: New video: Larry Brumfield's block thread test

Funny story about this video: Someone posted it to VFF and a discussion ensued. I tried to register there to respond to the discussion, but I somehow violated an obscure TOS during registration and have now been banned from VFF. Oh well! One less forum is probably good for my health anyway.
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Old 02-15-2021, 03:07 PM   #16
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Default Re: New video: Larry Brumfield's block thread test

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Originally Posted by alexiskai View Post
Funny story about this video: Someone posted it to VFF and a discussion ensued. I tried to register there to respond to the discussion, but I somehow violated an obscure TOS during registration and have now been banned from VFF. Oh well! One less forum is probably good for my health anyway.
If you really want to get on there, use a proxy.
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Old 02-15-2021, 03:11 PM   #17
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Default Re: New video: Larry Brumfield's block thread test

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If you really want to get on there, use a proxy.
I briefly considered it, but realized I would be this guy.

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Old 02-15-2021, 03:13 PM   #18
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Default Re: New video: Larry Brumfield's block thread test

So true....LOL
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Old 02-15-2021, 10:18 PM   #19
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Default Re: New video: Larry Brumfield's block thread test

What’s a TOS?
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Old 02-15-2021, 10:28 PM   #20
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Default Re: New video: Larry Brumfield's block thread test

"Terms of Service," like the rules for the forum. Apparently there is a rule that if you register, but have no activity after 15 months, it blocks you and you can't re-register. Not actually stated anywhere on the site. So I registered back in 2019 but then didn't post or visit. So now I'm banned. Who knew?
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