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Trouble with corner bolt(s)
#1
I've got a 1988 Nissan 300zx n/a 5-speed.  VG30 engine
Aluminum heads & iron block.

I had a combustion gas leak somewhere that was burning my spark plug wires and wiring harness,
so I change head gaskets.

Removed old heads and gaskets.
Cleaned out head-bolt holes, chased threads (with bottom tap).
Measured hole depth 33mm.   Measured bolt extends through bottom of head 25mm.
Head bolts  M10 x 1.5

Bought new set of EngineTech HB184 bolts.   FelPro PermaTorque gaskets.

Followed Factory Service Manual procedure exactly.  With click type torque wrench.

  tighten to 22fp , tighten to 45 fp , loosen all, tighten to 22fp , tighten to 47fp

All went well until I got to last bolt in corner, trying to tighten to 47 fp.

Torque wrench never clicked.   Thought maybe hole was stripping.    Took head
back off (in proper sequence).  Examined hole.   Threads good.   No looseness,
no binging when put bolt in.

Concluded bolt must have been stretching.

Does corner bolt have a lot more stress on it trying to pull down that last corner ??
I don't THINK these HB184 bolts are TTY, but not sure now.

Any thoughts ??
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#2
Hi Patrick,

The OE head bolts are reusable, they can be torqued to a final torque or to a final angle – Nissan gives a spec for both.

We cannot speak to the quality of other suppliers' bolts. It is possible that the bolt was stretching especially if it was one of the longer bolts in the set.

We recommend contacting EngineTech and explaining the issue to them, as they may be able to advise you on what they think happened with the bolt.

You should replace the head gasket from the side you removed the head from, as it has been compressed and will not compress again to conform to the micro-imperfections in the head and block sealing surfaces.
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