lele
Well-known member
Why service manual say they must be replaced with newers if u miss the correct torque?or in a engine head install?
cylinder head bolts
- Thread starter lele
- Start date
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eflyguy
Well-known member
Because they stretch, and will not provide the correct clamping force on the gasket, causing leaking or worse..
lele
Well-known member
Ok understand but...is ******* steel how is possible they stretch?
Viper Pilot
Well-known member
I guess you just don't understand stuff! This is not 'Superman steel', it's just metal and metal stretches if pulled hard enough. Try doing a little internet research!
BkerChuck
Second hand vegetarian
Hard as it may be for you to grasp, all metal stretches at least somewhat. It may only involve a few thousandths of an inch but that's all it takes. Consider it cheap insurance and always replace critical fasteners like head bolts and rod bolts when rebuilding an engine. Retaining the forces of compression and the rpm's these things can spin is a stressful job for any metal.
I still sometimes wonder if you're a troll sometimes. If you are--you're an entertaining one at least.
That said here's one video with a good example of how ductile steel can be. Imagine your over-torqued head bolt as the top example.
And as always, Google is your friend....
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lele
Well-known member
I'm not a troll. This section is techical discussion? Can I ask something?
RossKean
Well-known member
lele
Well-known member
Thank you Ross.
lnewlf
Well-known member
research "torque to yield bolts" and get edjumicated..
You bet! I even answered you with something specific and helpful. Wanna ask a follow-up question after you watch it?
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bigjohnsd
2021 BMW R1250GSA
The only Dumb Question is the unasked question. Been my motto for 60 some years, many really smart guys have thanked me.
lnewlf
Well-known member
what color is an orange?
eflyguy
Well-known member
wetwolf
Well-known member
ding ding ding, we have a winner. How is the knee doing?
putting a motor together so that it will last whilst putting up with your thrashing can be a hard thing to do. Especially when you want to be able to ride 700 miles and not have to call your buddy 2 states away. DAMHIK.
Yup, google is your friend.
Lele, i know nothing about tensile strengths and all that ****, and i ain't gonna youtube it. So here is my .02.
In the old days, you would bolt the heads, or head on, and run the bike or car for a bit and then go back in to retorque the head bolts just to make sure that every thing was squished down evenly after the motor had been heat cycled a couple times. Time marches on and the engineers figured out how to make better gaskets, more uniform casting and machinig of motor components, tighter tolerances and yield strength of bolts.
nowadays, you can bolt the head on, do the required torque setting and just run the thing. To tell you the truth, the smaller and more compact all fr our mechanical **** is getting, I'm pretty glad I dont have to go in and retorque head bolts.
Hope that helps.
Da Wolf
lele
Well-known member
Sorry guys my ignorance..I ask this because I bought a used cylinder head that comes with original bolts and they seems perfect..
eflyguy
Well-known member
They may look perfect but if they were used, they must be replaced.
Of course, you could always try them. How hard would it be to replace them if the gasket leaked, and you got water into the oil system? You'd have to pull the entire engine apart again anyway..
(.. and it's not ignorance! I bet you're not the only one who didn't realize these must be changed!)
Of course, you could always try them. How hard would it be to replace them if the gasket leaked, and you got water into the oil system? You'd have to pull the entire engine apart again anyway..
(.. and it's not ignorance! I bet you're not the only one who didn't realize these must be changed!)
lele
Well-known member
<blockquote class='ipsBlockquote'data-author="eflyguy" data-cid="1363807" data-time="1493719094"><p>
They may look perfect but if they were used, they must be replaced.<br />
<br />
Of course, you could always try them. How hard would it be to replace them if the gasket leaked, and you got water into the oil system? You'd have to pull the entire engine apart again anyway..<br />
<br />
<br />
(.. and it's not ignorance! I bet you're not the only one who didn't realize these must be changed!)</p></blockquote>
...my other bike service manual (honda vtr1000f) say nothing about the change and both bikes use M10 bolts..
They may look perfect but if they were used, they must be replaced.<br />
<br />
Of course, you could always try them. How hard would it be to replace them if the gasket leaked, and you got water into the oil system? You'd have to pull the entire engine apart again anyway..<br />
<br />
<br />
(.. and it's not ignorance! I bet you're not the only one who didn't realize these must be changed!)</p></blockquote>
...my other bike service manual (honda vtr1000f) say nothing about the change and both bikes use M10 bolts..
Torque to yield (TTY) bolts are relatively new. It is quite possible that your VTF doesn't have them.
