Do I absolutely need a hole in the pipe plug that's behind the timing chain?

 

Only if you want your timing chain to live a long time.

 

I didn't see any in the plugs into removed. It has an oil slinger. I dont' believe many other engines do this. Is there poor oiling to the chain?

 

Engineers will only provide a design that is absolutely required, and nothing more.

The .040" hole is there because the timing chain gets little to no oil otherwise.

No oil = quick wear = warranty costs.....results in unhappy customers.

The very same issue is why there is a .040" hole in the rear plug for the distributor gear.

 

The plugs behind the timing cover are not pipe plugs. They have a straight cut thread vs the taper cut of a pipe plug. Pipe plugs (taper cut) go in the back of the block at the ends of the oil galleys. One is solid, that you can see at the rear of the block and the other is behind a core plug. It has the hole in it to oil the distributor gear.

 

Btw, the oil slinger is there to keep oil from overwhelming the front crank seal mostly and has a secondary job of throwing what minimal oil gets on it from the hole in the plug.

 

"Many other engines" are not Oldsmobiles. Every engine made was designed with certain design constraints and assumptions. ***-U-MING that just because a Chevy motor does something a certain way, you can do that on an Olds motor has led to a lot of failed rebuilds.