View Full Version : blew oil out of dipstick

10-22-2010, 03:15 AM
On my last ride of the season with the GT I was going WOT for about 10 minutes and realized afterwards my sbc blew some oil out of the dipstick- not much, about 0.1 qt or so (it looked horrible because the belt was throwing it around everywhere).
Checked the breathers-fine, compression all good, just one wit 5% less than the others, not too much oil inside...

Any idea why this happened? I connected both breather hoses with a t-bar and went with one hose same diameter in my air scoop- mistake?

It was my last ride of the season anyway, so I can easily start searching for the mistake over winter but any idea where to start with?

10-22-2010, 07:09 AM
If it is an older style block with the dip stick on the #1 cylinder side that is common, I had it happen a few times until I put an slight bend in the dip stick.

10-22-2010, 02:06 PM
it is an older block, guess early 90's.

Just bend the dipstick? That would be an easy repair :)

11-15-2010, 07:57 AM
If this has never happened before, I'm going to bet that bending the dipstick won't do much.
Whenever I see this in the field, it's usually because one of the pistons has burned a hole in itself, forcing combustion gases into the crankcase. This builds up pressure and will blow oil out the tube.
I hope this is not the case...

11-16-2010, 04:05 PM
I experienced the same - replaced PVC hosing from valve covers to manifold - that cleared the issue

joseph m. hahnl
11-16-2010, 04:23 PM
I connected both breather hoses with a t-bar and went with one hose same diameter in my air scoop- mistake?

Start here. The vent tubes are for positive crank ventilation. Take the tee fitting out and run two separate hoses with or with out check valves.
one hose will vent out and one will vent in creating a flow circuit

This Video will explain why you are loosing oil through the dipstick and how to remedy it.

11-17-2010, 04:29 AM
ok and thanks, hope it is the mistake with the tubes- not a burned piston... will find out next spring when it is getting warmer :boggled:

11-22-2010, 06:10 PM
A hole in a piston would have shown up on the compression test and caused a miss in the engine. WOT for 10 minutes would cause the oil to heat up and thin out , then with the ventilation system you are using, a build up of crankcase pressure from the hard run (normal) and no where for it to escape fast enough, the pressure escapes at the weakess point, the dip stick tube. This is a crankcase pressure and oil escape route on trucks and cars with a plugged pcv valve or clogged ventalation breather filter. Switch to a pcv system, pcv valve in one valve cover to carb or intake vacuum and breather in the other cover. Hope this helps