Rear main oil passage in 340 block

[CRUZE 418]

I was reading about oil mods in a stroker book, the article said not to forget to put a freeze type plug back in this passage, it would cause low oil pressure. Don't remember taking one out, and had good oil pressure, 60's ? The passage goes to the oil filter, it has to, right? The hole in question in the picture is the first hole to the left of the oil seal, facing forward from the back of the engine.
What up?

 

[xLURKxDOGx]

I was reading about oil mods in a stroker book, the article said not to forget to put a freeze type plug back in this passage, it would cause low oil pressure. Don't remember taking one out, and had good oil pressure, 60's ? The passage goes to the oil filter, it has to, right? The hole in question in the picture is the first hole to the left of the oil seal, facing forward from the back of the engine.
What up?

View attachment 1715539131

Unless you or the machine shop takes it out it’s still going to be in there.

Jake

 

[rustycowll69]

I'm not sure it would affect oil pressure as much as it bypasses the oil filter, so you are circulating unfiltered oil. If I'm wrong, I'm sure someone here will correct me.

 

[dodgy]

Yep theres a solid plug in there, just poke something down there to measure where it's at, then you can check from the outside back of block that's it's at the intersecting oil passages, should be in between the out to filter and back from filter passages.

Red dot

 

[krazykuda]

The plug should be about 2 1/4" deep in the hole...


How to Rebuild a Small Block Part 3: Install Water Jacket and Oil Galley Plugs

 

[nm9stheham]

Or around 7-1/2" down from the top hole where the oil pressure sensor installs.

 

[AJ/FormS]

There is a step in the passage that make it difficult to drive it in too deep.... but I guess not impossible.

BTW
if you have an A-body; putting studs in the oil-pan rail will make it extremely difficult,if not impossible, to remove the oilpan, in-frame.

 

[CRUZE 418]

Ok guys, I got it! I have put a light into the hole and can see that there is no plug in there. This engine had not been together very long ( I bought the car last year) , big problems with the top end valve train, so decided to tear the engine down to see what other issues might be present. The oil in the engine looked like black paint, now I know why. Glad that I read the article that prompted me to ask, otherwise I would have put it back together and had the same oil problem. The freeze plug install pictures really spell it out too. If I have any other questions, I will ask.
Thank you again!

 

[CRUZE 418]

To AJ/Formula S, I have Gerst front suspension, will the oil pan rail studs still be an issue? Or is that a problem with a stock K-member?

 

[CRUZE 418]

I take back my previous answer, the plug is in there, I miss understood. So I am good to go.
Thank you again

 

[67Dart273]

This is a "famous" discussion. There are several old threads on here about this with photos. There is a way to insert a wire from the top through the oil sender port and measure that. I've forgotten the measurement, 7" and some I think. You'll have to search that. This is an important plug, something that many "Chevy based" shops don't seem to know about

 

[dodgy]

While you have it apart it's worth while to learn how and where the oil takes its path, get yourself some thin wire like mig wire and thread it through the oil passages and see where it comes out, it may give you a better understanding how they oil.

 

[CRUZE 418]

Will do. Bought a small brush kit to chase the passages before final cleaning.