Excessive blow-by?

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Jan 27, 2007 | 04:19 PM

fmc400

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MSEE

Joined: Apr 2004

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From: Austin, TX

Excessive blow-by?

'77 351W here with close to 110K on it. I'm having issues with the PCV system. I get quite a bit of yellowish goo in the hose that goes from the valve cover to the air cleaner. If i pull that hose off the breather filter, there is so much of the goo that it drips out. The same type of goo shows up at the end of the dipstick each time i check the oil. Sometimes it coats the inside of the dipstick tube. What is this stuff? If i rev the engine, smoke comes out from the oil filler cap, and if I pull the breather hose off, smoke comes out of there too. It's always done this, even after a new PCV valve.

When I bought the car a while back, there wasn't a hose running between the valve cover and the air cleaner, and no breather filter. I had to add all this. The PO ran a long hose from the valve cover grommet straight to the ground. I guess I now know why?

What is this goo? I guess my rings are worn pretty bad? Are there any high-mileage tricks I can do to at least help out the blow-by?

Jan 28, 2007 | 11:41 PM

sheltrow

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Joined: May 2003

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I inquired about this problem on a previous post (read "goopy 302"). No one seemed to have an answer. I have added a "drip tank" on the hose from the breather filter to the valve cover to try to catch some of the water that could go back down the hose to the valve cover-just go to the auto parts store buy yourself a 5/8" tee, some heater hose and an old 5 quart oil jug. Insert the tee right outside the air cleaner and route the hose to the jug. Just make sure to seal the hose entrance into the jug and make sure the cap is on the jug. You wouldn't believe the condensation you'll catch!

As I stated in my previous post I've had a couple of 302's like this that exhibited this sign. (One of those from day one.) Never really seemed like it hurt the motor any-but then of course I change oil every 1000 miles or so come winter time.

Jan 29, 2007 | 12:17 PM

fmc400

Thread Starter

MSEE

Joined: Apr 2004

Posts: 10,386

Likes: 35

From: Austin, TX

Thanks for the feedback. That is a nifty idea. I think what I'm going to do, when I get some free time this week, is just run some 5/8" hose from the valve cover grommet to the ground, like the PO had it set up. I guess it worked for him. I have so much white smoke coming out of the PCV system that I guess it just needs a place to dump. I do notice that when I run the engine with the PCV system open, the vehicle does much better on the highway. Probably because originally, the PCV valve shut off at low vacuum and all that smoke had nowhere to go.

I agree, it's mysterious how these motors can have such bad blow-by. My dad had a '79 F-150 with a 302 in it long ago, and I remember the blow-by was such an issue that the truck used to spit up oil into the air cleaner. On a side note, I've got a '73 Galaxie with a 400 in it, and over 150K on it...way more than my Windsor has on it. That thing doesn't burn a drop of oil, and has never had any blow-by whatsoever. Oh well. Thanks for your advice!

Feb 2, 2007 | 09:15 PM

sheltrow

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I was going to have my 302 rebuilt. I took the truck to my rebuild guy (excellent man to work with and honest). He listened to the engine run and asked if it used oil. I told him it didn't. He said that I would be wasting my time rebuilding it-he said that more than one 302 (more like dozens) that he has rebuilt have done this before and after the rebuild. Carbed motors only.
Apparently the really cold temps we get here in the winter cause it. He just said to keep an eye on the oil - if it gets really discolored change it-at least every 1000 -2000. He also rebuilds engines for a lot of boats that run Lake Superior. When the water temps are really cold in early spring he said that lots of the engines will get this sort of thing happen to them. It's not really blow by per say but rather extreme temps-namely really cold air or water in the boats case getting into a warm engine. I guess I can believe that as my 302 doesn't exhibit any condensation problems until there are steady temps in the low teens or colder.