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Think that you're head bolts don't stretch?

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Brosky

Brosky

Great Pumpkin
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My car has 55,000 miles on it. The head was retorqued at 1,000, 30,000 and 50,000 miles. These are but three of the studs that show how much they can stretch over time.

This is why ARP says to retorque (5) times as part of the final setting before running the engine. No w I doubt that their gardened studs move this much, but they definitely moved over that (5) times up and down process from 60 -70 lbs.

I know that the book says 80, but they say 70 because they use a lube and the book is for dry torque settings.
 
I'm not denying that the bolts (studs) stretch, but that looks to be about a 1/4". I find that hard to believe. Besides, if you look at the stud on the right (the shorter one), it has less threads on the top then the two on the left...how did that happen?? /bcforum/images/%%GRAEMLIN_URL%%/hammer.gif
 
Art, I don't know how or why it happened, but that's the original studs that came out of the block. I'll have to get a better picture and actually match the studs up, for a thread count.

Could it be that I had different size studs in from new to start with?? All of the nuts seemed to be the same above the head before we took it apart.
 
I think that two of the head studs are supposed to be slightly longer, to accommodate an air pump or air conditioning compressor. Sure I read that somewhere recently, but I cannot for the life of me remember where.

Cheers
Alistair
 
All of the ARP bolts are the same and I think (could be wrong) that the TRF part #'s are all the same too.

I'll check this out more thoroughly tomorrow and if I made a mistake, I'll certainly correct it.
 
I didn't decode it all, but the TRF catalog shows 3 different length head studs for TR6 in 5 different sets. All of the sets listed for US-spec cars have either 1 or 2 studs longer than the rest. The non-US sets are all the same length.
 
I needed a few studs for a rebuild and ordered them from TRF. The ones I received were not correct by a long shot. I had to use what I could find at a hardware store. The hardware store had all sizes of good studs, what a surprise.
 
Looks like my Boo-Boo!! Sorry for the bad info......

But then why do I only have one that's shorter than the others?

Could they have possibly cheated me at the Triumph factory? I wonder if I could get my money back???
 
Beats me, but I don't believe they could possibly be stretched that much without showing some serious damage. Might not fail entirely, but you'd see the difference in diameter where they stretched.
 
Randall, As I said, I just saw the difference and took a quick picture. When I have time, I'll check it out further and correct what looks like an error on my part.
 
I don't think that stretch means distort. There is a certain elasticity. That is where the self-tightening comes in.
 
Can mean either one. "Elastic" stretch (meaning the bolt/stud springs back after the load is released) is normal and required for a strong joint. But it's certainly possible for them to become permanently distorted and in fact it's important to check for distortion in the threaded area when you reuse old studs. It usually happens right where the threads leave the nut, which means it can give you a false torque reading (because the nut hits the distortion). The test is to spin a new nut down the threads, and if it binds roughly 2/3 down, the stud should be replaced. I've found several on my TR3A (and we won't discuss who overtorqued the head nuts /bcforum/images/%%GRAEMLIN_URL%%/grin.gif )
 
Having been raised from infancy with metallurgists and engineers I can say the studs you've shown are NOT longer due to tensile distortion, Paul. That much stretch (as Randall said) would have to change the diameter of the studs noticably. Steel behaves about the same as taffy in a visual sense: stretching it will result in a reduction in diameter somewhere along the length. Head studs would usually fail and fracture at a stress riser (where the threads stop) before they'd stretch as far as that.
 
Doc, I have to agree. I have to get all of the studs and put them together and then figure out where that one odd ball came from. When we took them out, there was no care given to location, because I was going to replace them all anyhow.

As they were laid out, it seemed that two were longer, but I'll bet that I screwed up and need to line them all up to find that I have one that is just shorter.

Bad post on my part for not taking the time to lay it all out.

The good news is that the new studs and head worked well after driving 150 + miles at 70MPH and up. No leaks and plenty of power. I surprised a fellow in a Jag, who I snuck up behind on the way to the show today. After we registered, he had to come over to look under the hood to see just why I kept right up with him, no matter how far down his pedal went.
 
Tr6's, starting around 73 had two longer bolts installed on the right front (manifold side) of the engine. They are there on my 73 spare engine which has never been apart and not on the 250 engine in the car. According to a post on 6-pack, they where provided for an AC option.
 
Brosky said:
Looks like my Boo-Boo!! Sorry for the bad info......
Click to expand...

The concept was correct, just stretched a bit too far ... /bcforum/images/%%GRAEMLIN_URL%%/lol.gif
 
Brosky said:
Could they have possibly cheated me at the Triumph factory? I wonder if I could get my money back???
Click to expand...

You have to keep in mind that the British Pound Sterling was severely undervalued against the Greenback at the time these cars were built, they obviously decided to save money by giving each car one shorter head bolt /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
Gentlemen, I stand corrected. I dug through some older picks that could zoom in on and there they are, right side of the head, as clear as the nose on my red face....

Next time rule, lay out parts twice, take picture once and then think about post for awhile before typing!!!
 
hehe. Easily forgiveable, Paul.

Nippin' at th' heels of that Jag shoulda been a bit o' fun! /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Nippin' at th' heels of that Jag shoulda been a bit o' fun! [/QUOTE]

It was certainly worth the embarrassment of this bad post. That was a LOT of fun. Especially when I told him that I caught him after I finished filling my tank at the gas station that he passed 5 minutes earlier.

He and I had a good time kidding each other. I told him that I was just beginning to cruise in O/D and had plenty of pedal left, in the event that he wanted to try it again going home.

It was the black one. Both are frame off, drop dead stunning beauties.
 
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