New TF heads, the head bolts keep breaking

Are you using moly-lube or 30wt oil? The TQ specs are different for each. I can tell you now that if you're going with moly, the torque specs you're using are way way way off. Over the phone, they told me that I should be torquing my 1/2" studs to 90 lb-ft. 302Ws use 7/16" bolts, though. So unless you've had everything tapped out to 1/2", I'm guessing you're running 7/16"s.

So, you're going so far passed yield that you should pull all of the bolts back out, including the ones you've already torqued down. Once you pass yield, it actually hurts the clamping load. Also, when the heads go through heat cycles they expand and coupled with cylinders at full pressure, the added forces will stretch the bolts. That's a normal process, and bolts are supposed to return to their original length when you remove them. However, once you've gone passed yield, they will not. So when the bolts will stretch, they will not return to the proper length, and you will be increasingly likely to develop sealing issues at the head-gasket.

I know you didn't ask for that explanation, but I just wanted to dissuade you from any notion of just replacing the bolts on the side you're breaking them. Call ARP directly and ask them what you should be TQing them to. A quick glance at their catalog indicates to me, that the numbers you are using are way off, even with 30wt oil.

Just out of curiosity, did you chase the holes with a tap?

As already asked, Are you using any lube or the correct lube? Are you sure those are the correct torque numbers? Are you sure that the threads in that one hole are clean and not gaulled up? Bolts shearing are usually caused by improper lube and over-torqueing. I would definately suspect the rest of the head bolts if no/wrong lube was used or if over torqueing happened.

The ARP bolts have a radius under the heads.
The washers that come with the bolts have a chamfer cut in them. The radius under the bolt head mates up with the chamfer
on the washer. Fail to do this and the bolts will never torque down properly. All the bolts get antiseize under the bolt heads,
and everything but the short head bolts get it on the threads. You need Teflon pipe dope or ARP sealant to coat the threads
of the short head bolts. The short bolts go into the water jacket and will seep coolant if you don't use the sealant.

V8_Kind_Of_Guy said:

The spec sheet says to go up to 110 ft-lbs on the final torque down.

Click to expand...

Are you sure it isn't 110Nm? That's equivalent to 81lbft.
The lower bolts should be torqued to 100Nm or 74lbft.

Along with the other great ideas, how is your calibration?