What has been your experience and technique on retorque of the head nuts when a new head gasket has been put in place on the pushrod engine? The factory service manual comments on initial torque, but is silent on retorque after a few heat cycles. The factory head gasket was single layer copper without o-rings or multilayer. The factory first service list does not include retorque of head nuts at time of first owner delivery and break-in.
I placed a Cometic-supplied Victor Reinz single layer gasket in my engine recently. After 100 miles and four heat cycles, I have just taken the rocker shaft off and checked torque of head nuts. All came up to 62.5 foot-pounds of torque with no fresh rotation of the nut to get there. I did not loosen the nuts before retightening at this point. I just put the torque wrench on and took it to 62.5 ft-lbs on all 14 nuts without any nut movement noticed by me. I thought I would inquire here about any next step.
Can you comment on your experience and technique, for single layer gaskets and those with o-rings or multilayer?
That’s all I’ve ever done on a variety of cars with c.i. heads. In nearly all cases there has not been any further movement of the nuts. I tried slackening one or two once, but they only returned to their previous position. Some people say they re-torque when hot but my opinion would be that unless it’s a specific factory recommendation, I wouldn’t do it.
As a point of reference, the expansion coefficients for steel and c.i. are so similar that there is unlikely to be any real difference in gasket loading between cold and hot. However, aluminium is quite a bit more and would theoretically increase the force on the gasket when hot.
I just had a memory bubble burst. I had a '60s era Renault and I seem to recall that it required re-torquing after a rebuild but I think this was because the block had wet liners and the gasket had a coating which ‘moulded’ around the block and liner joints.
Agree, with a cast iron head and single sheet copper gasket, there should be no need to re-torque, although a check can’t hurt. The gasket is compressed and the studs are stretched, but still within the elastic range. A re-torque would just be confirming that you did it right the first time.