Underneath the oil dipstick tube, just above the oil pan is an non-threaded 1/2" hole. It goes straight into the crankcase. Does anyone know what this is and how to plug? Seems an odd location for a freeze plug. I find no mention of it in the factory manual or parts manual diagrams for the engine. My interweb and forum searches have not turned up anything.

 

A picture might help.

I'm guessing this would be a 300/6 out of a '76 F-100/150? Just making sure.

 

I guess a photo would help clarify things. The block is a '78 date code.

Here is picture:

 

My engine is in storage and the pics I have of it are not good enough to determine what goes in that opening. Sorry. Maybe some other inmate will chime in.

 

Just thought I would follow up on this in case anyone else runs into this quandary.

So I was able to look at another 300 engine. It's not the easiest to see if a motor mount on, but it is definitely a small plug. Based on this, I picked up a Dorman 1/2" expansion plug (Dorman part # 362605.1) and installed it with a tiny bit of black RTV. I used a bolt fitting close to the same internal dimensions of the plug to tap it into place.

Obviously, it is for expansion, but I'm not sure I understand the rationale of its location. If anyone has ideas on this, I would be interested in hearing them.

 

The pictures I have of my engine are with the motor mounts (which is why I can't tell what's there - they've since been removed). I also checked my Shop Manual and the hole is shown in various images/drawings but nothing indicates what it's for or if anything goes there. I wonder why yours was open.

 

Same here on pictures I have the motor mount bolted to the motor
I never knew there was one on that side of the motor
Good thing it is into the crank case and not water jacket as I replaced all the freeze plugs on the other side as I had 1 leaking.
I then found 1 had been replaced with one of them rubber expanding type and the others were paper thin.

Wonder what the thinking was for that hole?
Dave ----

 

Mine was open because the block is fresh from the machine shop. They installed all new plugs as part of the work and probably just missed it when they were installing the new plugs. I'm glad I caught it before my break-in start up or that would have been a bad day. Certainly reinforced that "check, check, and recheck" concept for me.