What's this for on my engine block?

[bp71k5]

Anyone know what the thing in the picture is and if it should have oil in it? (circled in green)

While I've got the tranny out, I am taking some advice and trying to locate an oil leak on the engine. I found a hole right near the distributer which has some oil in it. My finger is pointing at the thing I'm talking about in the picture. The actual opening of the hole is on top of the engine. The view in the picture is after the flywheel was removed.

The PO said that the engine was rebuilt recently, but the "guy" forgot to keep a vent open and all the oil seals blew and he had to replace all of them. It doesn't leak that much oil, but I'd rather fix it if I can while it's all apart. Should there be oil in this thing? I can push my finger down into the hole about 1 inch before I some oil and what feels like dirt.

 

[01maroonz71]

kinda hard to tell, but my oil press. sending unit sticks up right about there....is the hole going up and down????

 

[BoondocK5]

Right there where the middle of your fingerprint in the picture there should be a threaded hole for an oil pressure sender. If the PO forgot to install something in that, anything else he did should be suspect too...

 

[01maroonz71]

but if htere's no sensor there, where's he get his oil press. reading from????

 

[bp71k5]

Yep, I can see the threaded fitting for the oil pressure guage right in front of it. I broke it off while taking the tranny out.

After some cleaning, this just looks like a cavity in the block. There's no fitting or hole at the bottom from what I can feel. My best guess is the pressure sender was just leaking and filling up this hole. Maybe I'll get a gm book out and see if I can find out what it actually is.

 

[ryan22re]

My guess is that a pre PCV block. Should be where the draft tube goes in to blow crankshaft gasses out the back and under the car.

Anybody more familiar with the older blocks confirm this? Also note the top hole on the bellhousing is tapped. Maybe that it a clue?

 

[ryan22re]

Quickly confirmed:

http://www.carcraft.com/techarticles/chevy_327_small_block/index.html

 

[bp71k5]

Thanks, that's exactly it. And it's a 327 too(block numbers say it's a 327 from 1967). Am I missing a tube that fits into that hole? At least I have a name for it now.

If it's supposed to be a way to relieve crankcase pressure, no wonder the thing leaked oil. The hole is so filled with gunk, I can't see how anything could get through there.

 

[4X4HIGH]

It was used for a road draft tube to remove crankcase vapors to the atmosphere. You can install a freeze plug in the hole to plug it up as long as you have a PCV valve in one valve cover and a breather tube from the opposite valve cover to your air cleaner base. That cavity has a horizontal passage that has a breather under the intake manifold.

 

[bp71k5]

Thanks, I was getting a little worried. I think I see what happened. When the PO swapped this engine in, he must have plugged this hole and then used non-vented valve covers which caused his trouble.

The driver side valve cover now has a PCV valve with a tube going to the carb base and the other valve cover has a tube going to the top of the air cleaner.

Thanks everyone, that helped. Now, I also found one cause of my oil leak is from both valve covers at the PCV holes.

 

[88$PIT]

While you have easy access to the back of the intake manifold, check to make sure that you still have a good seal between it and the block. After R and R of my top end I wound up with a small leak just under and to the right of the distributor there in the picture. (Looks like a little oil there already!) I was able to clean the area with some carb cleaner and push a little more black RTV into the gap and took care of it.

 

[bp71k5]

Yea, I have a feeling there's lots of spots on the motor that could use attention. It's good advice, but I want to keep the motor repairs limited to what's necessary and easy. If I see something obvious, I'll fix it.

I'm purposefully trying to stay away from doing anything with the motor until all this drivetrain stuff is done. (I know, I know, it's never done!) I half trust the PO who said it was rebuilt 25k miles ago. It seems to run strong with only the oil leaks being the problem for my driveway. I do want to try and make sure to fix any rear engine leaks so the clutch doesn't get fouled up.

The long term plan is to get a 350 in it with TBI so it still looks close to factory, and won't die on steep inclines. Maybe if it's not done in time for BB07, I'll have another year to tear into the motor.