The Stovebolt Site Forums The Shop Area General Truck Talk Oil seep from filler cap

Is a little bit of oil around the filler cap normal? 261 engine, I put 6 quarts of oil in, it has the full flow filter.
No blowby, freshly rebuilt.
Oil dipstick shows just a hair over full if it sits all night but once oil is up in engine it's normal.

Is the road draft tube plugged up? That would cause the engine to leak from places it shouldn’t.

I can't imagine it is, it was totally stripped downnduring the rebuild.

Does it have a pcv system or road draft?

Yep, it has a road draft.
I figured it was common. The oil filler cap is nice and tight and had a rubber seal so I dunno what would cause it.

Post some pics of your engine if you can.

I have a 261engine from a 1955.1 truck that has a closed PCV system.

Not much, just enough to kind of make a mess.

It looks like oil vapors are escaping from the vented cap due to pressure in the engine. The road draft tube creates vacuum to exhaust combustable vapors from the crankcase. The vented cap allows clean air in to replace the vapors.

Cleaning out the road draft tube is generally not part of a rebuild unless it’s a known issue to the builder. I would remove it and see if you can blow thru it.

What year is the engine?
Are you sure your rocker shafts are not on upside down? That will spray too much oil in the top end causing this.
Incorrect rockers for the year of engine can also cause this.

1961, not sure about any of it, had an engine builder rebuild it for me.
Where they repainted the road draft I can't imagine they'd do that without cleaning it first but I will check and see.
Can you check the rocker shafts without taking valve cover off?

If you pull the filler cap with it running and warmed up, maybe a little above idle, you should not see an oil stream shooting out of the rocker vent hole.

Ok, will do.
Yeah, no stream shooting out.

How much driving time do you have on it? Rings seated?
I have a 55.1 & 59, both with factory PCV system.

Had same problem on my 37 Buick which is like a 235/261 Chevy with two more cylinders. Converted road draft to pcv and now can you can work on with white gloves.

Probably about 300 miles after break in oil change

Take it for a drive, get it up to operating temp. Make several runs WOT up to speed & closed throttle decel (on a safe road). It may not have seated the ring if it has only been run with light engine load.

A compression test would tell if a ring has not seated.

Not likely- - - -maybe a cylinder leakdown test would be a better option. I'm guessing that the engine just needs to be worked like a rented mule for a few hours to get the rings seated properly. These engines aren't the fragile wildflowers most stovebolters believe them to be. "Drive it like you stole it!"
Jerry

Will do HotrodLincoln

That's the way I was taught. Guy I worked for would say "If it's going to come apart better now than later".

That's the way I was taught. Guy I worked for would say "If it's going to come apart better now than later".[/quote]

I had a 300 I6 in HS and college. I punished that thing, floated valves, didn't change oil, etc. It always started, and always came back for more.

Unless your builder was born in the '30s, it is unlikely that he would know how to test the road draft tube, let alone how to clean one.
It is not the easiest task to clean one either.

Are we just talking the black pipe that sticks out of the engine? Or something within that feeds into it? Looking in the bottom of that black tube it looks clean as can be. Otherwise, I have no idea.

52Carl I used to send those thru the caustic boilling tank along with the rest of it. In the garage would burn them out with gasoline or throw it in a wood fire or the burn barrel.

Burning tracks Might lower the oil level a pint ,see if it helps. If the crank is hitting oil can make more oil vapor than is needed that might slobber out a little. My 235 is well worn from real work hauling corn and leaks like territory marking but doesn't leak at the cap. Even the rear main that was disturbed when I turned in -.002 bearings doesn't leak exsessively never even thought about putting in a new bottom half. That one is probably an old asbestos braid one. Might look at that baffle inside the block where the roadraft pipe goes in it might be sludged up gotta take the pan off to get to it but can see it with the tube out. Held in there with screws that show on the outside I think.