C3:Engine Head hardware

[Steve L.]

I was removing my left head last night on my original L48 73 coupe. (The engine seized due to a 15 storage). I noticed that the rocker nut styles are not consistant. Most nuts have a step on the non-mating side, while others have a conical shape - looks almost like a wheel lug nut.

In addition, the conical washers just under the nut (between the nut and rocker arm) are different. Most are flat on the top but some have slots almost like it was intended to put a big screw driver into it.

Why is there inconsistancy. No one has touched this engine since factory.

Steve L
73 coupe since new

[Joe L.]

Re: C3:Engine Head hardware

Steve----

Both style nuts and rocker balls were used in PRODUCTION and SERVICE over the years and both nuts are a form of prevailing torque locknut. The "conical" shaped nut that you describe used a thread deformation on the upper surface provided by 3 triangular shaped indentions which generate the locking action of the nut. This form of locknut is sometimes called a "Stover" nut. My 1969 300/350 was originally equipped with this type of nut at all rocker arms. I can't tell you the part number for this nut at the moment.

The "stepped" locknut that you describe uses a different sort of deformed thread. In this design the upper portion of the thread is deformed into a slight oval shape. This thread deformation provides the locking action of the nut. This is the nut that has been sold in SERVICE by GM for many years and was also used at times in PRODUCTION. The part number for this nut is GM #3744341. It is discontinued and replaced by GM #465934 which I do not know the configuration of.

The rocker ball differences that you describe are also a change that occurred over the years. My recollection is that the rocker balls before about 1969 had no groove and those after about 1969 had the groove. Incidentally, the groove is designed to increase the oiling of the rocker ball by allowing drip oil to travel to the rocker stud and, thence, downward to the ball seat. NO GM small block rocker arms ever had grooves on the ball face, though, as many aftermarket "high performance" rocker balls do.

I'm sort of surprised to hear that you have both type of balls AND nuts on the same engine if the engine has never been serviced with replacement parts. It's theoretically possible that both style nuts were used in the engine plant at the same time, but I doubt it. I really don't think that rocker balls with and without the groove were ever used in the plant at the same time except during the time when the changeover from one type to the other occurred. I don't think that happened in 1973. Are you certain that these parts were never changed?

[Steve L.]

Re: C3:Engine Head hardware

When I think back 30 yrs, I did complain about lifter noise when I first got it, so I took it to a dealer. They had it for a day while I was at work. They told me nothing was wrong.

They would have had the opportunity to change out some hardware. If they did they didn't tell me. There was that single opportunity that the hardware could have been changed. I guess I'll have to retract my earlier statement that it was never touched??

None of that area ever gave me problems so for once the dealer was right.

73 coupe since new