Head bolts

[evil_twin]

The head bolts are torque to yield bolts... how many times can you reuse them? They are brand new found oht the head was cracked after I installed them. They have zero miles on them. Anyone?

Sent from my SPH-L720 using Tapatalk

[nando]

zero.

a new set is like $25. seriously.

[Cabriolet]

no bolt that is torque to yield may be reused ever.

when you tighten tty bolts they plastic deform, an irreversible deformation of the bolt.

http://en.wikipedia.org/wiki/Deformation_(engineering)#Plastic_deformation

[evil_twin]

Thank you! Thats what I thought but wanted to double check

Sent from my SPH-L720 using Tapatalk

[nando]

in before a r3vtard posts how he's re-used M20 TTY rod bolts to save $50 on his motor "rebuild". :p

[jalopi]

Aren't metric blues like, $30-40 and reusable? Seems like the smarter route. TTY bolts are weird imo.

[Cabriolet]

The McMaster Carr's have a tensile strength of 125,000psi and rockwell hardness of c27
Metric blues have a tensile strength of 176,900 psi and Rockwell hardness of C38
The ARP2000's have a tensile stregth of 220,000psi and rockwell hardness of c46

Metric blues are definatley not reusable just incase anybody wants to know..

also dont use metric blues. i've seen a ton of people that crack them in the block

[nando]

Aren't metric blues like, $30-40 and reusable? Seems like the smarter route. TTY bolts are weird imo.

metric blues aren't headbolts. they're some random bolt that happens to have the same dimensions as the M20 bolts. Yes, they've been used. No, I'd never use them. TTY bolts are superior for a number of reasons. if you're going to try something different, go with a stud that's meant to be used as a headbolt.

[ForcedFirebird]

in before a r3vtard posts how he's re-used M20 TTY rod bolts to save $50 on his motor "rebuild". :p

Again, to save a few pennies in comparison to a rebuild.

[SkiFree]

Again, to save a few pennies in comparison to a rebuild.

[digger]

what was the issue with the original hex head bolts that were "recalled" years ago? was it a fault from the manufacturer i.e. quality?

[nando]

yeah, they were defective. they weren't TTY I don't think either.

[digger]

yeah, they were defective. they weren't TTY I don't think either.

from memory they were basically the same as any average 12.9 hex head bolt. basically a metric blue but with out the hex socket head

[ForcedFirebird]

They weren't TTY IIRC, but they did require heat cycles between sequences.

[redlightpete]

The head bolts are torque to yield bolts... how many times can you reuse them? They are brand new found oht the head was cracked after I installed them. They have zero miles on them. Anyone?

Sent from my SPH-L720 using Tapatalk

Actually you might be ok reusing these. Certainly the installation causes some damage to the 'bolts', but this may not be significant. I'd be more worried about the fatigue damage done during countless heat cycles than any deformation during installation.

If you had an extra new bolt you could do a little experiment to verify. Just install the bolt using the correct torque-angle procedure and remove it. Do this over and over again until the bolt breaks. Divide 1 by the number of cycles it took to break the bolt. This would be the approximate % of the fatigue life that is used up during installation. So if it takes 50 cycles to break the bolt, you're using up 2% every time you tighten it, and installing it a second time isn't a biggie. If it breaks in 4 cycles, then everyone else is right and you should spend the $25.

I used the same two old rod bolts to plastigauge the six rods on my motor. I tightened them with the recommended torque angle method each time. So those tolerated 7 installations with no problems. Maybe If I get motivated I'll go out and perform this test with those TTY bolts and report back.