I am assembling a 67 L79 and found a picture showing an object under the intake manifold in the galley.

I think its called a breather tube or oil draft tube. Can some one enlighten me on its purpose - do I need to install one?

thanks

 

yes.... it keeps oil out of the crankcase vent

 

aka...."tomato can"

 

Thanks guys - I will be sure to install one.
Do you empty out the tomato's first! ha ha

 

ALLLLLLLLLLLLLL 55-67 Small Blocks had this can under the intake manifold.
It is a vapor seperator. It's purpose is to allow crankcase vapors to be seperated from the oil, then they pass along to the hole in the rear of the block. The 55-62 engines (EXCEPT Calif delivery) had a road draft tube attached to this hole and the crankcase vapors exited the engine to the atmosphere.
The 63-67 engines (and 62 for Calif cars) had an adapter attached at the hole (there were various adapters, depending on engine configuration) and then the adapter was fitted with a hose and PCV valve which was connected (usually at the carb base) to an intake manifold source. Some engine configurations had a breather tube between the air cleaner and that hole, and then there was a fitting on the oil fill tube at the front and a hose/PCV valve connected to that fitting.
In 68, the hole in the rear of the block was eliminated and the valve covers got holes in them (YUK!!!) for an oil filler cap and PCV connections. The oil fill tube completely went away for 69 and oil was added in the valve covers. That was the very beginning of cluttered looking engines----------------------and it got worse from there.

Tom Parsons

 

Not like in the civil war huh Tom? Men were men and women were afeard. Always get a giggle out of your altitude.

 

Don,
The last SB that I built with the vapor canister (a 66 engine), I carefully drilled the spot welds which held the outer can and the inner baffle together and seperated them. I obtained a commercial stainless steel scouring pad (from a restaurant supply service) that is used in restaurant kitchens for cleaning big cooking utensils, and stuffed it inside the baffle. Then I had the baffle and outer can welded back together again. My reasoning for doing this was so that the stainless mesh would serve as a filtering mechanism to improve the seperation of vapors and oil. Seemed to work pretty good.
The engine was a 66 327 that I stroked with a 350 crank by having the main journals turned down to 67-earlier small journal size.
That was the 350 that USED to be in the 56. When I built the 400 for the 56, I sold the 350 to John Neas.

Tom Parsons

 

You can still get reproductions of the can:
http://www.parts123.com/parts123/yb....Z5Z5Z50000050x

 

Now that is rediculous!!!!!!!!!!
Chevy made 8 bazillion of these engines (265-283-327) with the canister. They should be tooooooooooo easy to scrounge up!

Oh ya, you don't want one from a 55 265 because they were the long version and may interfere with the underside of later manifolds.

Tom Parsons

 

Most people have never seen a '55 block with the one-year-only crankcase vent holes in the bellhousing end of the block for the road draft tube through the left side.

 

Do these vapor cans ever go bad and is there a way to test them? I occasionally get an oil burning exhaust smell.

 

There's nothing in them to "go bad" - it's just a steel can with a baffle in it that can never rust. An oil-burning exhaust smell is usually valve stem seals or rings.

 

Tom,

Thanks so much for the details, and your experience. I will definitely follow your advice. I already "unknowingly" bought the vent tube that bolts to the top rear of the engine and connects to the carb last summer at Carlisle.

r
Don

 

John,
Do you also have a picture of the long, 55 only, vapor canister? I don't, or I would have posted it side by side with the 55-67 style.

Wish I had a picture of the canister I took apart and filled with the stainless mesh. It's a work of art, if I do say so myself!

Tom Parsons

 

Thank you, Tom, for validating my suggestion in a much earlier thread that this was an easy way to add cubic inches to a 327. I suggested this and was then told that the 350 crank journals were bigger, to which I responded with a roll eyes emoticon.

A big to you!

 

Welllllllllllllllllll, you're not as brazen as I am, so I have no problem standing up and looking the "no nothings" straight in the eyes!
But, believe it or not, I remember your comment about stroking a 327 with a 350 crank---------------------mainly because I have personally done it as well as stroked a SMALL journal 327 with a 400 crank to build a 383 from a 327 block.
One additional thing to mention about dropping a 350 crank into a small journal 327 block (after the mains have been turned down), is that the flange BETWEEN the rear main journal and the journal for the rear seal of a 350 crank has a slightly larger diameter. Thus, the outer diameter of that flange also needs to be slightly cut down because the groove in a SJ block/cap is smaller than the groove in a large jorunal block. From there, the engine is built up just exactly as a 350 would be built.
And by the way, as I pointed out earlier, that 327 stroked to 350, now resides on an engine stand (where it's been for a few years) in John Neas warehouse. He bought that engine for the intention of installing it into his factory 270hp/3sp (converted to a 4sp MANY years ago) 57 Chevy Bel air. John says that's a back burner project. He has so many irons in the fire, he can't decide which one to pull out first. And now that he owns 3 vintage Top Fuel dragsters, that's what is getting his priority attention now. Right behind the dragsters is the total frame-off on his matching 58 big brake Vette. Then the frame off on his wife's 57 4sp Vette.

Tom Parsons

 

Nope, don't have a photo of the '55 can; I'm sure yours had your typical "aircraft" attention to detail.