R75/5 Engine block questions. Holes in the case?

[jjwithers]

I cleaned my fully gutted engine block a bit this weekend... and had a few questions while doing so.

1) there is a pinhole (circled in red) in the oil pump area. What is it for? I could easily see something that small getting clogged with gunky oil after the miles get put on.

2) those hex plugs (i think they were used when the engine is cast) circled in Yellow. I always thought they went straight through the case but i couldn't see where they have any effect on the inside of the engine. Do they? Is it OK to remove them? Or is it best to leave the seat/bond it created after 40 years unharmed?

3) Lastly, i seem to have a small hole under my starter (circled in red). is that normal? It doesn't go through the case. just to a hollow area. Should i be concerned?

Thanks in advance.

-josh

[Duane Ausherman]

The (yellow) hex plug is just that, a plug. To do the machining, they must drill there and plug it up when done.

If they aren't leaking, leave them as is. Very few leak enough to bother one.

[SteveD]

What's the ragged line in the middle at the bottom of the top picture?

[Deleted User 62]

I checked one of my /6 cases and it doesn't have the one under the starter. It looks like a casting flaw, most likely passed as a non issue by the person doing the inspection. That jagged line SteveD mentioned looks to be more casting related too. Perhaps where two parts of the mold meet? Note the difference in surface texture on the left and right of the center.

[Rob Frankham]

As Duane says, the hex plug is just a plug... but, what he doesn't say is that it has a definite purpose. It actually plugs the open end of an oil gallery drilled into the block. If memory serves, that particular plug seals the gallery that takes oil from the oil pump to the filter.

It's also worth knowing that the two studs holding the timing cover on at the front also seal the ends of oil gallerys. In this case, the ones that take the oil from the front main bearing to the rocker gear...

As you will appreciate, its quite important that these plugs remain in place and oil tight.

I would also be inclined to say leave them alone unless they are leaking.

Rob

[StephenB]

What's the ragged line in the middle at the bottom of the top picture?

I'd say it's a crack in the case ...

[Major Softie]

What's the ragged line in the middle at the bottom of the top picture?

I'd say it's a crack in the case ...

Very hard to tell from the photo. Could be a crack. Could just be a flashing line.

[jjwithers]

It isn't a crack. You guys had me freaked out so i looked it over. It is just a line from the casting. The motor was made in either 70 or 71. they probably got better with the casting quality as the years went on.

Nobody has any information on the pinhole in the oil pump? I'm just curious as to what it is for... because it looks like an intended hole.

[George Ryals]

I just went down to my basement shop and looked at a '76 block. It has the same hole. The hole is on the pressure side of the oil pump. It appears to me that it is there to squirt oil on the lifters/cam the instant the motor is turned over to crank. Make sure it is clear before assembling your engine.