Head bolts
 

I have a 2000 mustang gt. I recently did a piston change on my motor. I put the car back together. I bought new arp head bolts and used them. I was doing the break in and after about 5 min i heard a knocking sound. I have the engine out out the car and am taking the heads off to get them checked. Does anyone know if i can use these bolts, i know they are strech to yeild but i wondering since they have not been on for more than 5 min and not through heat cycles if they will be ok. Thanks

The dealer loves to tell you they are a one use item. However you will find many people reuse them 2-3 times before they get a new set. Case in point I replaced a head gasket on my car and reused the head bolts and that was 3 years ago.

Thanks man...thats what i was hoping to hear!

I mean I would reuse them once more no problem on low HP level cars, such as 400rwhp and less, but on higher HP cars you might wanna get some studs.

My friend works at a garage and they never reuse headbolts on 4.6's and 5.4's. However on older chevrolet engines they said it was okay to reuse the headbolts on like 5.7's etc. He said the head bolts wouldnt retorque back to factory specs. I dont remember what he said it would cause. But i dont have a 4.6 nor have i worked on one. But my buddy is biased twoards chevrolet. Dunno if any of this helps.

if you have ARP fasteners then you can reuse them if they're not TTY. I would find a new set if you're using factory bolts.

As an engineering student, when people say this, it makes me want to kill myself. There's a reason why they are Torque to Yield. The bolts are tighten until the metal starts to yield. While this doesn't pose a strength issue necessarily (metal work hardens as it passes the yield point), it does cause the fastener to change length. Because of this, the fasteners will need to be torqued to a different spec in order to get the proper retention. This is why you never reuse TTY bolts.

If you have ARP stuff (didn't think they made bolts for our engines), then you can reuse them as they are not TTY.

Don't get me wrong I know how they work and for most people sure replace them. But lets be serious on many shit boxes like my g/'s old 94 Rodeo screw getting new ones at $150 when that thing barely makes 190hp. But I know you should not reuse them, but people do and I'm just saying I have done it to before.

Ok, now you guys have me guessing myself. One of the main reasons i was asking is because of the two step tighten...You tighten them down to first spec, then untighten one full turn, and then retighten to a lighter foot lbs, so to me that already would strech the bolt...These are the arp bolts and i have not quite a full heat cycle on them...Let me know...i plan on putting back together sat. Thanks

if you have arp bolts, then don't worry. I don't know of ARP making any TTY bolts.

FWIW, Many engine builders measure not just tq but also bolt stretch. The 2 step also makes sure that you're not getting an improper tq reading from minor galling of the threads or slight metal-metal seating imperfections and that the bolt has stretched some amount. Buddy from the powerblock shows likes to use .006 rod bolt stretch to verify his tq readings.

That's right, ARP doesn't make any TTY bolts/studs. In fact, if you did torque them to yield, I'm sure the threads in the block would break before the bolt yields.

As r3d said, the two-step is to ensure proper torque readings (which is why you always lube the studs/bolts). However, a tale-tale sign of tty would be torque it down, then tighten an addition amount in degrees.