Every GM small block I've owned has leaked a little oil, which I have come to understand is the norm.  Eh?

None of  the smalll blocks I have owned since 1978 have ever leaked

Do you mean an older engine? I always had problems with valve cover gaskets until i bought the longer hold down tabs for the bottom bolts. After that it was fine

I too am victum to rear main seal leaks and pan leaks.  But damn they are reliable.  I also had an oil fitting leak near the rear top part of the engine.  That was fun.  Ohhh the things I could do with a 3 car garage instead of a compact 2 car garage.

Quoted: Do you mean an older engine? I always had problems with valve cover gaskets until i bought the longer hold down tabs for the bottom bolts. After that it was fine

Yes, atleast ten years.  All my problems have been with the front and rear mains.

I have had the same problems.  Some people say they will always leak.

95 350 LT1, no leaks here

On all my small blocks and big blocks i have had over the years have had some leaks like my 454 i have a vale cover leak that is realy bad and i need to fix it befor i drive it into the ground.

<GM Service Advisor> They all do that. </ GM Service Advisor>

I beleive that the most common place that these engines leak is at the rear intake manifold where it meats the block and heads. People replace the gaskets and forget to put a big glob of RTV in the corners.

I thought it was part of the rust prevention feature of it.

I also notice that some from day one, puff a little oil at startup, not alot, but noticeable.  Mine does from time to time, but it does not seem to consume much oil.

No all of mine have been tight, i had one that was 25 years old and it didn't burn or leak, low miles but still fucking amazing engines.

If the mains in the engine are 20 yo you should have a problem.
However if quality rubber is used like Victor, and properly seated you should never have a leak.
I would eat off of any I ever built......dirty engines are a pet peave...

1997 350 w/35K miles and not a drop. I do have alot of water that drips out of the A/C dryer, but like DzlBenz said: <GM Service Advisor> They all do that.<GM Service Advisor.

Mine didn't start leaking a drop until about 90,000 miles, even then it's not much (no stain in garage yet, just a small drop on back of block).  Other than that it's a good solid engine even with gas at $2+ per gal.  

The 350 small blocks are reasonably powerful, reliable, moderate cost to run, and relatively easy and cheap to fix.  Not the most powerful.  Not the most fuel efficient.  Not the most reliable (IMHO I figure this goes to either a diesel or the Toyotas).  The 350 block is kind of like Glocks (that ought to keep the thread going for a while ).

Quoted: I beleive that the most common place that these engines leak is at the rear intake manifold where it meats the block and heads. People replace the gaskets and forget to put a big glob of RTV in the corners.

I have built several small blocks and have been around the street rod world for quite a while.  That valley gasket should be the first thing trashed out of the gasket set.  All I use is a bead of black RTV (silicone) sealant and it never leaks.  Another common leak is around the bolts from the intake to the head.  If the threads aren't sealed well, it will leak at the center bolts.

Rear seals can be a problem, but if you install split seals with a small dab of silicone at the split and then set them offset to the main cap split, along with placing a very tiny amount at the rear main split on the iron, it won't leak.  Also it must be installed in the correct direction and pre-lubed to prevent start-up burn.  

The later model rear main seal appliance that is a one piece seal can also fail if it isn't pre-lubed.  This happened in less than 10K miles with a factory assembled motor  (to me).

There is also a through-hole on the front of older blocks that allows you to install a long bolt to hold the fuel pump pushrod in place while installing the fuel pump.  Folks commonly forget to plug this bolt hole and oil will leak when you brake hard, particularly if you are a half quart high on oil.

Yes they can leak.  No they don't leak, if they are built correctly.

I have a 94 pickup with a 350 in it.  I don't have a problem with it leaking oil, I have a problem with it leaking water.  My driver's side head gasket at the front corner leaks water to the outside.  About once a year, I have to add stop leak to plug it up for another year.  

Quoted: I beleive that the most common place that these engines leak is at the rear intake manifold where it meats the block and heads. People replace the gaskets and forget to put a big glob of RTV in the corners.

YUP!

Even the friggen 4.3's are like this.

Alot of the times the small amount of oil that leaks back there never finds it's way to the ground.

One more thing, there is no gasket back there or in the front, it's all RTV.

The only gaskets in that area are over the intake ports left and right.
The valley front and back is straight RTV.

How about leaky valve guides/seals?

Now that was my problem.

M4-AK

1990 Chevy 350 V8 w/ 250K miles.


I don't know if it leaks oil faster than it burns it........or burns oil faster than it leaks it.


Anyway.....20W50 is your friend.