I bought a set (20) of new quality aftermarket head bolts and, when I started installing them, I noticed that the bolt heads of many of them had a fairly large run-out as I was threading them in by hand. I could also feel heavy spots - the bolts rubbing hard against the hole sides. When subsequently checked on a lathe (engaged the length of the thread that is threaded into the block, about 30 mm), I could see that more than half of the bolts were pretty much out of straight, up to almost 1 mm measured on the shaft near the bolt head. I then bought another set of 20 genuine Jaguar bolts (the price has now dropped to 2-3 GBP a piece) but the situation with their straightness is similar to what I had with the aftermarket ones, if not worse. On the other hand, all of my old bolts (the first generation with hex heads) are pretty straight.

Is this amount of out of straight of new bolts normal or should they be rejected? The recent price drop of genuine Jaguar head bolts (across all usual suppliers) from GBP 8+ to GBP 2-3 a piece makes me suspicious.

 

I suspect they are torque loaded straight - they are stretch bolts after all.