# Blowby Solutions



## pbearly (Apr 18, 2013)

Well I have my 64 which is running a 389 tripower. Last fall I changed from 256 gears to 390 gears and just started running it this spring, what a change in the vehicle. With that said I'm certainly running higher RPM's and I'm now noticing some blowby out the valve cover vents. It doesn't seem excessive, I just smell it slightly and I can see drops on the plug wires. So I'm wondering if this is common and how others resolved the problem. I am running a PCV and it is working properly.


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## geeteeohguy (Feb 2, 2008)

Only common with worn pistons/rings. Higher RPM's will make it worse. Only cure for it is to rebuild the engine, or at least a new set of rings.


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## geeteeohguy (Feb 2, 2008)

IF you do not have the baffles in the valve covers, oil could also be simply splashing on the breather and working it's way out that way. Does it smoke out of the dipstick tube at high RPM?


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## pbearly (Apr 18, 2013)

I'm betting there isn't any baffles in the covers, I'll have to check that. I do not notice smoke out the dipstick tube. I do have fantastic oil pressure, it carries 60psi warmed up which I think is a bit excessive but I don't have to worry about a lack of oil as long as the seals hold. I will have to do some more checking


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## geeteeohguy (Feb 2, 2008)

'67 and up used splash shields bolted to the heads that kept oil splash off of the breather port area. If you don't have these, consider using a breather that has enough packing in it to alleviate oil loss. This is assuming that your piston rings are indeed in good shape. You can perform a cylinder leak down check to verify the condition of the pistons and rings. If more than 10-15%, it's rebuild time.


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## pjw1967 (Mar 10, 2014)

I saw this in the '67 manual. If I understand correctly, loss of manifold vacuum under hard acceleration or constant high RPM's prevents the PCV system from working efficiently. This cause the crankcase to pressurize, blowing oil back up into the valve covers. I too get the oil drool on the valve cover after tromping on it, aided more now by going from a 3.23 to a 3.55 rear.


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## pbearly (Apr 18, 2013)

pjw1967 said:


> I saw this in the '67 manual. If I understand correctly, loss of manifold vacuum under hard acceleration or constant high RPM's prevents the PCV system from working efficiently. This cause the crankcase to pressurize, blowing oil back up into the valve covers. I too get the oil drool on the valve cover after tromping on it, aided more now by going from a 3.23 to a 3.55 rear.


Exactly what happened to me. I think mine is worsened by my valve covers, when I pull the cover I is direct accrss, no baffle plate to deflect it.


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## 666bbl (Apr 13, 2014)

Now wait just a doggone minute!! I thought the venerable GTO was supposed to blow by other muscle ca, uh, um, never mind...








I just had to, ya know?


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