y-block blow by..

R

reddog565

Senior Member
hi guys! I need your thoughts? I have a 272 (1956).
that I rebuilt less than a year ago. I'm running "trips".
the problem I'm having is, I'm getting a lot of blow by
from the oil filler tube! I know the engine is mechanically
healthy, as I rebuilt it. I have a pcv installed in the top
of the block. (not the valley pan). the road draft tube
has been eliminated.(blocked off). I understand, the
oil filler tube also acts as a fresh air intake. but, something
I'm not doing right, because there is too much blow by
thru the filler tube, thus fumes are getting into car..
I know all you guys are extremely sharp! so, I'm sure
someone has a fix.
thanks!!
 
reddog565 said:
hi guys! I need your thoughts? I have a 272 (1956).
that I rebuilt less than a year ago. I'm running "trips".
the problem I'm having is, I'm getting a lot of blow by
from the oil filler tube! I know the engine is mechanically
healthy, as I rebuilt it.

I have a pcv installed in the topof the block. (not the valley pan). the road draft tube has been eliminated.(blocked off). I understand, the

oil filler tube also acts as a fresh air intake. but, something I'm not doing right, because there is too much blow by thru the filler tube, thus fumes are getting into car..

I know all you guys are extremely sharp! so, I'm sure
someone has a fix.

thanks!!
Click to expand...

Can you show a photo of the PCV SYSTEM install?

If she is pumping fumes out of the filler cap, it is either non-functional and/or has extreme blow-by.
 
The pcv valve is next to distributer.
 

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Has the engine been having this issue ever since you installed the PCV system, or did it start later on it's own ? Even after a fresh rebuild things can happen to cause more blow by.


Sal
 
I can't tell where your hose is connecting to in the block from that picture. What you should be trying to do is to ventilate the crankshaft.
Best way is to have openings at opposite ends of each other in relation to crankshaft. The original ideas of having the oil filler cap with an integral filter and ventilation tube/screen cannister in the lower block is good and the other being at the back of valley pan instead of the tube is okay also.
 
Sorry guys, couldn't get a better picture .as
I stated previously. The pcv valve is tapped
Into the block. It's vacuum is supplied from the
Port between ctr. And front carb. I'm wondering
If I should put the road draft tube back on it?
Such as Dave said about having ventilation
At opposite ends. Does anyone have a good
Canister and tube?
 
reddog565 said:
The pcv valve is tapped Into the block. It's vacuum is supplied from the
Port between ctr. And front carb.
Click to expand...

Do you mean the PCV install is as shown below?
 

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Yes kultulz. That's exactly what I have! I'm thinking the engine is not breathing properly so it's just blowing it back out of the oil filler tube?
 
reddog565 said:
Yes kultulz. That's exactly what I have! I'm thinking the engine is not breathing properly so it's just blowing it back out of the oil filler tube?
Click to expand...

You do not have an effective system. The valve has no baffling and will ingest spray/vapors making the system ineffective.
 
I had a PCV valve in the valley pan without sufficient baffling. It pick up a lot of oil, which on my set up mainly ended up in # 7&8 cylinders. But that was into the rear carb fitting on a 4 barrel. A stuck PCV valve will also produce your symptoms, to the point of blowing out a valve cover gasket in extreme cases. (Ask how I know, and the mess of oil on the exhaust is almost as bad as the heart attack when all the smoke shows up).

What engine was that PCV designed for? Did it mount vertically in the OEM application?

How much oil is the engine using, and how many miles since the rebuild?
 
I believe the pcv valve was supposed to be
For a y block application.the engine doesn't
Use oil. There's probably a couple thousand
Miles on Rebuild.
 
reddog565 said:
Yes kultulz. That's exactly what I have! I'm thinking the engine is not breathing properly so it's just blowing it back out of the oil filler tube?
Click to expand...


Let me be more concise, the setup @ the carb is fine. It is the actual valve setup that is ineffective.
 
what kind of rings did you use.i had trouble with a set of moly rings.the first time i saw a pcv in that spot i wondered.the dist, spinning in the cam gear is going to throw a lot of oil around.most of the top end oil is running down there.
 
darrell said:
...the first time i saw a pcv in that spot i wondered.the dist, spinning in the cam gear is going to throw a lot of oil around.most of the top end oil is running down there.
Click to expand...

Exactly! Good point ...
 

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Thanks for hanging with me guys!
This is an issue that needs to be resolved,
I can't breathe those toxic fumes... Can't
remember what type of rings are used?
Pcv valve#255.
 
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