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Y-block blow by?

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'49 bomb!
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I guys! I have a blow by issue, the engine is a 272 rebuilt completely. I'm running a trip set up on it. It's basically stock rebuild. The issue I am having is; I'm getting a lot of blow by out of the filler tube and also collecting oil in the breather cap! The engine is healthy as I just rebuild it! It has a steady 18 pounds of vacuum. It has a PCV system on it.which basically consists of a PCV valve tapped into the back of the block and that's basically it. I really need some suggestions as to how to fix this problem.
Thanks to all...


darrell
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i see you have another hose hooked into your system.i dont think thats a good idea
oldcarmark
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Is the PCV direction correct. What is the hose  'Y'ed into the pcv Hose for? PCV should be One Hose only.

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'49 bomb!
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You're absolutely right about the T-off hose. The one going to the right in the picture is for my vacuum brake booster.
Unfortunately I only had two ports on my manifold fitting, so that's why I had to T off of the main vacuum line.I tested the PCV valve direction by taking the hose off at the manifold port and drawing air through it and it was open. So that tells me when the manifold is creating vacuum the PCV valve is opening and sucking the fumes out.
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If the PCV valve is connected properly and working, its apparent that the blow by is overcoming the PCV.  That's way too much for a new rebuild as you claim.  18 inches (not pounds) of vacuum is a little low.  I usually get 20 or more buy your gauge may be off.  The first thing I would do is to check compression.  I suspect a piston/cylinder problem.  A compression test will confirm that.  It could also be a head gasket, or other obscure things.

Good luck,

Bill A
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Cliff
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Rings have not seated yet, if they are chrome may take up to 7500 miles, cast or molly should seat right away. do not tap into the PCV line, find another way, you can make a plate to go under the center carb. to pick up vacuum
oldcarmark
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'49 bomb! (11/17/2019)
You're absolutely right about the T-off hose. The one going to the right in the picture is for my vacuum brake booster.
Unfortunately I only had two ports on my manifold fitting, so that's why I had to T off of the main vacuum line.I tested the PCV valve direction by taking the hose off at the manifold port and drawing air through it and it was open. So that tells me when the manifold is creating vacuum the PCV valve is opening and sucking the fumes out.

If You have 2 Vacuum Ports what is the other One being used for? Is there not a Vacuum outlet at the back of the Manifold?

http://forums.y-blocksforever.com/uploads/images/b9ec8c4e-313b-486f-b1b0-422e.jpg http://forums.y-blocksforever.com/Uploads/Images/a82cee8f-be33-4d66-b65d-fcd8.jpg  
'49 bomb!
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No port back of manifold! I know T off
Is not the correct thing to do. Pass.side
Is for pcv& vacuum brake booster.
Driver side is for distributer advance &
Trans. Vacuum modulator..
DryLakesRacer
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If it was me I would remove all 3 carbs (maybe the manifold too) get 3 spacers having the center one tapped for a 1/4" pipe thread. You need to have a 3/8" hole tying the 2 sides together so that your engine vapors (blow-by) go to both sides of your engine. You can do this with a notch between the barrels on the bottom. The outside 2 could be phenolic and the center aluminum all could be the same height. Feed your PCV system from there and your power brake booster from the one you have now.
It's hard to do with 3-2's but you should have a hose from the oil breather/fill pipe to the top of the center carb where the air enters air filter. When working correctly there shoud be a vacuum on this line or on the top of the fill tube to hold a piece of paper when idling.
I installed hundreds of "smog devices" at Sears in the early 60's and this was one on the checks. The AC brand unit was the best which had a carb spacer that the PCV valve screwed into. Today most of what we scab in don't have pipe threads. Good luck.



56 Vic, B'Ville 200 MPH Club Member, So Cal.


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