Thanks guys! I have not done it yet, I'm going to have to wait until next weekend. I'll hammer it in with a 2X4 so there is no possibility of driving it in too deep.

What would I do with OSO?

And yes, I have examined the block very carefully,. It is the only thing that was left out (I hope ).

I am getting ready to do the same thing. I have a Dart Big M block and there is a generous step in the block which would appear to be for the plug to bottom out on. The cam is probably .100" from this step when it is all the way pushed back. So should I drive it onto the step bottomed out or just leave it flush to the block? Is the consensus that some aviation sealer can be used on the plug before installation or just put on externally after it is installed? For the record my motor was purchased as an unassembled kit. On most kits like this the rear cam tunnel plug is left out to help in setting cam end play. I will say it would have been harder to set the end play with that plug in. Thanks for the advice.

Craig

Not to be an alarmist, But......
If the shop let it go with that plug missing, what else did they leave out?? Maybe nothing, but now is the time to check. I would give the engine a thorough once over...Twice! I say this because I made an assumption that everything was all right after finding, and fixing a "Minor" problem on an engine. I assumed that was the only thing the builder missed. Needless to say, I swung the engine twice! Always nice to be sure.

In my case the cam tunnel plug was intentionally left out for ease setting cam end play. I built the motor and now need to put it in. If I were to forget to put it in that would not be good!!