cevans wrote:
LMWatBullRun wrote:
There is also no reason to replace the stock bolts, either, as long as they weren't stubborn to remove and you used a 6 pt socket. The head crushes before you reach the yield point on the factory bolts, so the only reason to replace them is if the undersized bolt head is messed up. Take a look at the ARP stud thread page 5 and you will see what I mean.
While I can't speak to the yield point on the bolt versus the head gasket, re-using head bolts REALLY sounds like a bad idea. All my years of automotive work I've never heard anyone ever suggest it.
If the bolts were in fact initially torqued to the yield point, then you would be correct, this would be a very bad idea because of the potential that retorquing would stretch the bolt to the failure point. But this is not the case with the CRD, because the head itself YIELDS in compression before the tensile fastener (bolt or stud) reaches the yield point of the TTY head bolt. At 140 FPT, the torque value for ARP studs corresponding to the yield point of the factory 'TTY' bolts, the head was compressed at the glow plug holes enough to make
removal problematic. The head yielded locally and generally before there was sufficient tension on the fastener to cause yielding of the factory bolt. You can also see this from the behavior of the factory bolts on the head itself. If the factory bolts did not yield, then there is no point in buying new bolts unless the bolt heads are degraded. Just to put the the final nail in this argument, once I get LIbby 1 back on the road, I will weld up a fixture and torque a factory bolt until it yields or reaches 250 FPT whichever comes first, with measurements and pictures, and we can all see what happens and how many degrees of rotation in a freely rotating fixture it takes to get to the yield point.
Which goes back to my point about the poor choice of head fasteners, and why ARP studs are a much better solution.
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