Blow-by

[macguyver]

I read an old post about fuel getting into the oil. It talked about an improperly sealed valley pan gasket. I don't have a fuel/oil problem but I do have serious blow-by. I recently replaced the intake manifold gasket but only sealed the cooling jackets like the manual said. Would not having the rest of the ports sealed tight cause a blowby problem. Yes, I am trying everything to get away with not having to rebuild!
Thanks for the help!

[rhamby]

Does the blow-by start immediately when you start running it, or does it need to warm up before the blow-by starts? A broken ring condition will sometimes not blow-by until the engine warms-up some.
If you had a seal problem on your intake you could get all kinds of conditions - smoking, fuel in the oil, blow-by, depending on what ports of the intake are leaking - that's a hard one to predict accurately to me. Somebody else may have a better idea to test which one it is. Have you checked the compression?

[64Trvlr]

<BLOCKQUOTE>quote:</font><HR>Originally posted by rhamby:
Have you checked the compression?<HR></BLOCKQUOTE>

That is a good place to start, then go on from there.
:cool:

[macguyver]

I just went out and verified, It does it at cold startup and gets worse as it warms up. My compression check about 6 months ago showed all cylinders to be up at about 150 with #8 being a little low at 130. The oil fill tube actually spits out oil under accelleration?
Thanks for the help, hope this sheds a little more light on the subject.
Chris

[Va-Rob]

Check the pcv valve, do you have the stock air cleaner, and is it vent pipe conected to the oil fill tube??? This can lead to something serious if you don't fix it. Most common promblem that arises from this is a blown rear main seal.


Rob

[macguyver]

The PCV valve is new and it is connected to the bottom of my Carter Carb. The oil fill tube vent is currently connected to my air housing. I am running a K&N air filter and the oil fill vent is connected to the bottom of the air filter base. I do believe I have a rear main oil leak. Sounds like it might be to late. I have great vacumm from the PCV line but I still get a lot of blow-by from the oil fill tube? Should this be true?
Thanks,
Chris

[rhamby]

Were you having the blow-by problem when you checked the compression last time? You know where I'm going... :(
What you are describing is exactly what you will see with a broken ring. The harder you drive it, the more oil that is going to get blown up the filler tube. In bad cases it will literally flow in and fill up your air cleaner.
I'm not saying this is the only possibility, but it sure might be worth checking the compression again now to illiminate that possibility.
Rebuilds are rare opportunities - relish them... :D

[porchpiggy]

I have been fighting this exact same problem. I don't understand what is going on. A 360 with 108K, I get 125 on a comp test, it does not use any oil, or smoke, the engine runs very clean (after 1000 miles the oil is so clean you can't hardly see where it is on the dipstick, and the PCV stuff is good.

One thing I did come across while trying to figure this out is that the PCV connection on the manifold can get caked up real bad so that the engine is not venting there. I did not have this problem because I installed a new intake. I used a can of "restore" oil additive, and it slowed the spitting oil out the tube down some.

[Va-Rob]

If you are friendly with a garage? You can have them use the exhuast gas anilizer prob on the oil fill tube with the engine running. Wrap a rag around the outside to keep out any outside air. Disconect the pcv valve and block off carb port. If there are any HC's then you know you have a leak somewhere in the combustion area either burnt valve "my bet is on that one" or gauled piston or broken ring. Other than that do the compression test again.


Rob