The Stovebolt Site Forums The Shop Area Engine Shop fumes out of the oil breather cap 235ci

Hey guys,

Yesterday I made the maiden voyage with my '58 Apache. I really enjoyed it!
It kept good temperature and oil pressure and wasn't smoking at all.
After my trip of 30 miles I wanted to unhook the battery just to be sure and then I noticed some fumes coming out of the oil breather cap.
Is that normal?

Thanks!

Jurgen

The engine was jus shut down after reversing into my garage.

Its common

....example...

Thanks!

Have you changed the oil (and oil filter, if you have one)?
Was there water in/with the oil when you drained it out?

How fast were you driving on that 30 mile trip?

How long were you travelling over 40 mph?
The road draft tube is ineffective under round 40 mph.

Go for a 30 mile trip at 50+ mph.
Better yet, drive 30 miles out and 30 miles back (at 50+ mph).

Like Dads50 said, it's common on any engine with a few miles on it. Today's engines catch the blowby and run it through the engine again with the PCV systems on the cars. If they didn't have those systems modern cars would smoke on shut down too. A popular modern "Mod" on new performance cars is called a "Catch Can" that harvests a lot of the blowby to keep it from going back into the engine. They think it hurts performance.

Well, it does in a way.
Oil vapor greatly reduces fuel octane, making the engine more knock-sensitive.

Well, it was my first drive and I don't think I drove faster than 40mph:-)

If you want to drive your truck often/regularly, and you will not be often/regularly driving over 40 mph, you might want to install a PCV system. Original PCV systems are hard to find (they started being used in 1948 on Chevrolet trucks).

I think that Deve has a Tech Tip on installing a PCV system on a 216/235/261? http://devestechnet.com/Home/PCVInstall

Millions of engines got by for decades with a road draft tube. All engines have at least a little blowby- - -there's no way to get a 100% seal with the piston rings. Yes, stovebolts are going to make a little vapor, and (HORRORS!) maybe even drip a little from the road draft tube. If it bothers you that much, buy a riceburner with a PCV system!
Jerry

It doesn't bother me at all:-) But I'm not familiar with such old engines.

It's more about maintaining the engine and removing crankcase gasses so they do not mix with the oil and cause premature damage. The road draft tube is advertised to begin working its Venturi magic starting at 30mph. So all the time you are running your engine before that, crankcase gasses are just collecting.

Since our vintages were the last years to not have PCV as a normal feature, it is easy to replace the road draft tube with a PCV system. It's a relatively inexpensive upgrade that you can do yourself.

I used Deve's suggestion on my 261. Easy and simple....as the draft tube I had was an older version with the oil cap on it. Cheaper to do the PCV.

If you have a significant amount of blow-by of combustion gases getting past the rings into the crankcase, you will need to be careful how you design your homemade PCV system. If you do it wrong you will have too much foul crankcase fumes re-introduced into the combustion chamber at the wrong time, causing poor performance.
I would recommend researching and looking at how GM designed the PCV system for the 230/250/292 engines and copy that as close as practical.
Carl

I like the idea of a PCV system and the pic of the setup looks good,but I have 2 questions. I was talking to a hot rod friend today and telling of the PCV. He wondered if bringing in the oily gas at the center of the manifold would cause cyl 3&4 to foul the plug. Second I saw a oil fill tube on a 68 vette that had a cap and a fitting for the pcv valve to screw in. Would this work instead of the freezplug? Thanks for any idead.

Have you checked the crankcase ventilator tube (road draft tube)? It might be clogged.

My number 3 and 4 plugs look no different than the rest of the bunch.