Torquing heads, not the 70's band !

[DamianZ28]

Hi all, how many miles would you do after refitting new composite head gaskets to check and re-torque the head bolts? Just asking as l have fitted tin versions and had number 1 plug out today and noticed coolent on top the of piston at TDC , have done 800 miles since full rebuild but embarrassingly forgot to recheck the head bolts.ooops, changed oil n filter at 500 miles. Have it stripped to fit new cam n lifters, heads off now to check but only number 1 pot had small amount of coolant in it, will fit new composite gasgets hence my original question.

 

[mrtask]

The first time I replaced my head gaskets I used the tin gaskets, a borrowed torque wrench, and re-used the old bolts. It didn't work.
I did it again with composite gaskets, new bolts from Rimmer Bros, and this time I borrowed a recently calibrated and certified torque wrench from a pro rather than just from a mate! I didn't have to re-torque the head bolts.

 

[SydneyRoverP6B]

Land Rover (Defender, Discovery, and Range Rover) were installed with imperial grade 8 bolts (identified by 6 radial lines on the top surface of the head when using tin gaskets. For composite gaskets, torque-to-yield bolts were used. Apply anti-seize to the threads, torque to 20Nm. Then rotate each bolt in the correct order through 90 degrees. Repeat, again rotating each bolt through a further 90 degrees. Unlike the grade 8 bolts, torque-to-yield bolts are not high tensile, and this process exceeds the yield point of the bolt resulting in permanent plastic deformation. For this reason, these bolts should never be reused, which is in contrast to the grade 8 bolts, which can be reused many times, given the torque required does not exceed the yield point. If your heads have 14 bolt holes, do not use bolts in the outer 4 holes; leave these empty.
Torque-to-yield bolts do not require further tightening at any point in the future, which is a distinct advantage, hence the reason Land Rover, BMW, and Nissan, to name but three use them.

Ron.