327 ??? Old block question?????

[69MyWay]

I am posting this here as the C1/2 guys are more likely to know the answer.

I am starting to go through the 23 T-bucket. We are going to convert the points to an electronic ignition.

I pulled the distributor and noted that this block is very strange.

It has some sort of an extra bit of casting, and vent tube coming up from the rear of the block right next to the oil pressure sending tap.

I can't seem to find any good numbers on the block. I assume it had been shaved down smooth for looks at one time.

So....what gives?

What all old small blocks would have this strange vent tube on the rear like that?

I took some pics and will upload later.

 

[allcoupedup]

It's for crankcase ventilation. All the 327's had them - not sure about the 283 and earlier V8s. This system was the precursor to a PCV system and valve. The stock setup included an oil fill tube at the front of the intake manifold. air was drawn from this tube by manifold vacuum at the carb. So that a vacuum condition would not take place, the block was vented at the back. A road draft or crankcase tube usually connected to a flame arrestor inside the air cleaner to allow that vacuum source above to suck in clean air. Many people simply stick a breather in this location.

Many C1/C2 owners that convert to 350s (note absense of this additional casting) have to find another way to allow ventilation. The typical fix is to drill a valve cover and install a PCV valve and connect to the back of the block.

Hope this helps. I've been watching for cheap 327s in my area for this reason alone. I'd love to go to a 350 (or a 383) but the absense of this crankcase ventilation casting (and my desire to keep the stock appearance) limits me to a 327.

Brian

 

[69MyWay]

Brian....

You da man!!!!!!!!!

I figured as much, but up until now I had only noticed the 327 with the oil fill on the intake. I had never noticed the vent on the back of the block as well.

This one is just a 90 degree street elbow kind of vent tube pointing at the driver side of the engine.

I guess I should get that hooked to the proper tube. It appears to have been belching oil residue over the years as it coated the back of the block and front of the trans with a thick layer of black goo.

thanks again.

 

[69MyWay]

C5d, we must have been posting at the near exact same moment.

 

[69MyWay]

Here is the pic.

 

[Tom Bryant]

Chris,

The one you have is a 283/327 fitting from the '63-'67 era. It connected to a threaded in PCV valve at the base of the carb or on the intake manifold, depending on application. Usually the front intake manifold mounted oil fill tube had a non-vented cap in this application and the air went into the crankcase through a tube into the air cleaner.

1962 and older cars and trucks used the old road draft tube. It mounted to the same place on the block but routed down around the engine bellhousing and was open to atmosphere on the bottom end. The length was set so that it was in the strong air stream that passed under the car which caused a vacuum or scavanging effect that drew out the crankcase emmissions and allowed pressure to excape. Shortening it for header clearance killed the scavanging effect.

It used to be common to follow and old car with bad rings and see a puff, puff of smoke coming from below the engine. Here is a 1957 Chevy 210 283 2bbl road draft tube. It served double duty as a plug wire holder.

Tom

 

[69MyWay]

The intake on this engine does not have the oil fill tube.

Here is a full shot of the engine.

I wonder how I should hook this up?

I guess I can always plug it and run a standard PCV????

As you can see, it only has MOROSO breather caps on each valve cover.

 

[Tom Bryant]

Guys used to just put an expansion plug in the the road draft tube hole and use valve cover breathers like you have. Where did this T come from or did I miss a post somewhere?

Tom

 

[rowingone]

If you dont have crankcase ventilation . . . what are the negative effects . . or is it just for pollution control?

 

[69MyWay]

Guys used to just put an expansion plug in the the road draft tube hole and use valve cover breathers like you have. Where did this T come from or did I miss a post somewhere?

Tom

Take a look here:

http://www.corvetteactioncenter.com/forums/showthread.php?s=&threadid=39581

 

[Tom Bryant]

The crankcase must be vented. Pressure from piston ring blowby will cause oil to come out around every gasket and seal if not vented. Plus the fumes built up in the crankcase are highly explosive. Hard on oil pans.:L This is why we keep our pcv valves service regularly.

The PCV system is an active system in that engine vacuum draws fumes from the crankcase and rounts them through the intake to be burned in the engine. Fresh air is constantly being drawn in through the breather so there is a steady flow of air through the crankcase.

The valve cover breathers (passive system) will work fine in this case. Anything to allow the fumes and pressure to excape.

Tom

 

[Tom Bryant]

What a great story. It looks like you are going to have Brasso fingers again. Actually I kind of like the "patina". But then I don't own much that is shiney. :L You need to preserve that old Turkey Run sticker when you restore the windshield frame. That's like still having an old SCTA timing plack on your hot rod dash.

Tom