Inline six oil blowout - need help

[Mark B]

Oil blowout happened after 40 minutes of highway travel. My truck is usually driven short distances, so this was a long high speed run in comparison. I was motoring along when the engine started to sound bad and wheez. I immedialty pulled over and shut it down. There was engine oil on the underside of the hood near the firewall, and on the firewall. Most appeared to be on the passenger side area and the passenger side of the engine toward the rear of the block. No oil showed on the dipstick. I added two quarts and it measured full. The engine started and ran fine. No oil leak was observed when I ran the engine at speed (I had someone to look under the hood while I raced the engine). I drove home Ok without a problem the next day, but at a slower speed off the highway.

This same thing happened a year ago - the last time I drove in a similar way on the highway - but without the visible mess of oil. It just seemed to have disapeared.

I don't drive the truck enough to know if it burns oil. A little probably, the engine is original and runs a little dirty. But it certainly is not a smoke belching pig!

Any idea what is going on to cause this?

thanks
Mark