396 head bolts

[Daniel W.]

Does anyone know of a reason NOT to retorque the head bolts on a 396 engine?

I am following Clem's advice and replacing the valve springs, retainers and keepers on our engine (20720). I have an opportunity to retorque the head bolts at this time with the rocker covers off. Any reason NOT to retorque the head bolts?

Found the retainers were the "O" labeled retainers referenced in a July 1965 Chevrolet Service Bulletin as being early 396 and should be replaced. The retainers were determined to be the root cause of engine failures back in early 1965. Also found all keepers were copper colored. Thanks Clem, they will all be replaced with purple.

[Clem Z.]

i would not retorque the head bolts

just check the torque on the rocker studs and replace all the rocker arm adjustment nuts with new ones. keep all the rocker arm ball with the rocker they came from as they "wear together"

[Michael H.]

Re: 396 head bolts

Yes Dan, there are a few reasons why you probably shouldn't retorque the head bolts after the initial torque and many miles of servce. One is the fact that the sealer on the head bolt threads has taken a set and if the bolts are rotated, even a little bit, the seal is broken. The most important reason tho, is the fact that even if the amount of pressure on the gasket may have changed slightly, the amount of cylinder deflection near the area of each bolt has stabilized and the piston rings have taken a set, or broken in, to that particular shape. As head bolts are torqued, the top of each cylinder tends to cave in just a little bit around the area of each bolt, producing a slightly pentagonal shape instead of a true circle. (It's amazing how flexable cast iron is) This area usually wears away while the ring is still breaking in and if it changes, you wind up starting the breakin process all over again but now most of the soft face of the ring is gone so it may never again seat completely. All of this is, of coarse, for use with the proper steel head gaskets. If for some reason the engine has composition gaskets, retorquing IS necessary and that's one of the reasons why I don't like comp gaskets. GM recommends no retorque is necessary for steel gaskets.

[Daniel W.]

Re: i would not retorque the head bolts

Thanks Clem.

[Daniel W.]

Re: 396 head bolts

Thank you Michael. They are the original steel gaskets.