head bolts....

[FEnatic]

Do you guys reuse head bolts or are these supposed to be one time use, like so many of today's products?

[fredtam]

I replace them each time I pull the head.

[Here comes trouble]

In consideration of expense, I would question how much metal fatigue has occurred in a set of L6 head bolts and ......how often...they should be replaced due to ordinary use or even occasional high speed efforts. I know around 1974 there was a spectacular difference in Datsun 4 cylinder head bolts to some very strong ones (that did not know how to break) identified by a slight circle indentation round the allen head hole. A record kept of head bolt torquing would indicate the need for replacement of the bolts needing attention.

[clarkspeed]

I only use the Turbo bolts, Nissan Comp sells them as high strength. They have the circle. I tend to change them every full rebuild.

[zcarnut]

I’ve rebuilt about a dozen Z car L-series engines and changed out an additional twenty some head gaskets over the last 30 years. I have always re-used the original head bolts unless one had corrosion damage (rust pitting) on it. I have never had a problem with a head bolt that has been re-used.

 

In 1972 Nissan improved the strength of the head bolt and the new bolt was identifiable by a ring (or recess) around the top of the bolt. I would definitely change out any of the early head bolts with these later ones or the turbo head bolts. The turbo head bolts have a “13" stamped on the top of the head bolt and can the torque can be increased to 60 ft-lbs.

 

However, I always install new rod bolts during a rebuild as the consequences of a failed rod bolt are far more severe than a “stretched†head bolt.