Head Bolts ?

[MR2Jedi]

Is it NECCESSARY to replace the head bolts with new ones when re-installing the head back on the 3sgte ? or can you reuse the old ones if in good shape?

[alltracman78]

It's much safer to replace them.

I learned this the hard way.

[MRQtwinturbo]

i used ARP main and head studs when i rebuilt my motor...

[MR2Jedi]

^ do the ARP head studs use the same 12 point allen?

[WT Morgan]

I've re-used head bolts with no problem- but I agree the safest thing is to replace them. Factors do come into play, like how old they are, how many miles, how much boost, how long and hard their future service life is expected to be ...
Bolts stretch and keep a residual spring tension. If ever over tensioned they could lose their spring.
With time and the few extra bucks, it is worth it IMO. If I HAD TO get going for some reason and didn't have new ones, I wouldn't hesitate to reuse the ones I took out (unless it had poor or stripped out threads or something major).
I like to recheck (torque) them after fifty or a hundred miles or so.
All ARP bolts I've seen and used have had the twelve point heads.

[toyotaspeed90]

rule of thumb....

if they are TTY (torque to yield) then replace them

if they aren't... you're good to go....




how do you know if they're tty bolts? if the sequence says "torque to XXlbs then XXdegrees then XXdegrees" then they are tty bolts.... if it says "torque to XXlbs" and nothing else... they are not tty bolts.....

the extra "turns' makes them "torque to yield" which means..... stretch bolts.... once they stretch they've been "used" and shouldn't be stretched again as they could snap during the torque sequence.... making life suck.....

[tHa kNiGHt FaLL]

Originally Posted by toyotaspeed90

rule of thumb....

if they are TTY (torque to yield) then replace them

if they aren't... you're good to go....




how do you know if they're tty bolts? if the sequence says "torque to XXlbs then XXdegrees then XXdegrees" then they are tty bolts.... if it says "torque to XXlbs" and nothing else... they are not tty bolts.....

the extra "turns' makes them "torque to yield" which means..... stretch bolts.... once they stretch they've been "used" and shouldn't be stretched again as they could snap during the torque sequence.... making life suck.....

torque to yield aka stretch bolts... strongly not recommended

typically a one time use bolts. i'd hate to do all that work to have to do it all again.

[MR2Jedi]

Originally Posted by toyotaspeed90

rule of thumb....

if they are TTY (torque to yield) then replace them

if they aren't... you're good to go....




how do you know if they're tty bolts? if the sequence says "torque to XXlbs then XXdegrees then XXdegrees" then they are tty bolts.... if it says "torque to XXlbs" and nothing else... they are not tty bolts.....

the extra "turns' makes them "torque to yield" which means..... stretch bolts.... once they stretch they've been "used" and shouldn't be stretched again as they could snap during the torque sequence.... making life suck.....

yeah, they're "TTY's" torqued 36lbs then 90 degrees...Thanks Tspeed90

Anyone know how much more $$$ the ARP's are over OEM?

[WT Morgan]

Good info.

Added info just to clarify for technical accuracy- bolts (and threads) stretch when torqued. The stretch helps keep bolts tight under vibration and expansion/contraction changes with temperature. It is when they are over stretched that they are definately spent. Metals have a MOE (modulus of elasticity) which is how much they will deform elastically before permanent yield. Think of how elastic a coat hanger is until it exceeds the MOE, then it is bent with permanent deformation.