spinning head bolts

[Kibokojoe]

Trying to install a m30 head cylinder on a 1991 735i. On my first attempt I had two bolts that would not tighten. So I removed the head and installed two Time-sert's. Put the head back on and now there are two more bolts that are spinning. Funny thing is there is absolutely no signs of stripping on the bolts or in the holes. Has anyone ever seen this before.

[Tiger]

Are you positive you are using an accurate torque wrench? Are those new bolts?

[Kibokojoe]

Oh yes it is a Snap-on calibrated torque wrench. And yes they are new bolt, Now I have 28 new bolts and two head gaskets.

[Tiger]

Wow... let me ask you... when you do the procedure for several steps of torqueing... are you saying it simply just stripped out before the specified torque is reached? Or is it you tightened it up and then all of the sudden cannot tighten at all?

Maybe it is just the luck of the draw that the threads are compromised by the previous owner/mechanic who might have use impact gun to tighten the cylinder head... that would explains stripped threads.

Other possibility is that the bolt is not quite the right spec... but hard to even think of this in modern time as everything is tight tolerance. If you thread these bolts in... does it feel solid as in no freeplay?

[whiskychaser]

I'd suggest dieseling but I've read enough of OP's posts to think he wouldnt have fallen for that one. So either the bolt is too small or the hole is too big (So to speak :-) ) Have you compared the sizes of the bolts you took out with the replacements? Any chance somebody tapped the block for bigger bolts?

[Kibokojoe]

Dieseling??? what is dieseling///////I think the PO must have chased the threads and oversized the hole. Could install Time-Serts to remedy this situation but I now know the block was run very hot and I think it was compromised. Yes I checked the old and new bolts on a gauge they are M12 x 1.75 threads. I have another block that we are going to rebuild/ I am looking into ARP studs instead of bolts. Going to have a machine shop go over the block to insure all is good then we will mount the block to the stand and assemble the motor. So far I have found two problems with using ARP studs. 1. it appears there maybe a problem with removing the head at a later date unless you remove the engine. 2. The ARP studs don't have a shoulder so the cam brackets can move. I have written ARP and asked if they have an answer for both of these questions.

[Kibokojoe]

Yeah they keep spinning on the second torquing sequence. I have heard that even the OEM BMW head bolts are junk that the only way to go is with studs

[632 Regal]

Torque them to spec, they sometimes just do nothing till they clamp down, Dont worry about an extra turn or two.

[632 Regal]

EEK! unless you have hydrolock going on! Make sure the holes are clean and dry except for the oil you use on the bolts to tighten them!