The Stovebolt Site Forums The Shop Area Engine Shop Put too much oil in rebuilt 250?

I just started driving it last week. I have 30 wt break in oil. I had put a little too much oil in it (1/2 qt) maybe. Before driving today I checked the oil and it was on the add mark. A half qt put it back on full. I see no sign of leaking anyplace. Could this be due to the rings are not seated yet?
Years ago my dad advised to speed up the let off the gas to sling expand the rings pressure I believe.
Also what radiator cap lbs should I be using?
Thanks!

A newly rebuilt engine will probably use a little oil, how many miles did you run to use a 1/2 qt. - 1.0 qt.? Was the exhaust smokey? Radiator cap pressure will depend on what has been replaced in the cooling system, new modern radiator and heater core? The 250 engine could run 8 - 14 psi but the rest of the cooling system may not be able to stand that pressure.

Changing load (speeding up and letting off the gas) helps the rings break-in.

Some engines (not sure about the 250) burn off excess oil (above the full mark) relatively quickly. That combined with the fresh rebuild I wouldn't do anything other than continue to check oil level often and record miles between additions.

Thank you, I ran less than 200 miles.
The radiator is basic original with no AC or power steering.
The cap is so easy to turn & remove but the radiator stays full and has a reservoir attached. There is no lbs pressure written on the cap.
No smoke from the exhaust but it did have a gray looking exhaust yesterday with water dripping out the pipe yesterday after driving, it cooling off then cranked up again. I’m thinking it is running somewhat rich.

Hi glennj3 . . . here's my take about your engine oil . . . .


It really could be those two PCV valves - - Do you know IF - you have any type of "baffels" , inside , under those holes where your PCV valves are ? ?
I really don't think I'd use two PCV valves ! ! For my 69 (Nova) 250ci , I use the stock PCV valves & have a Baffel under the rear location. You need too remove the front PCV valve . . . my guess , would
be - your Oil usage - - is being "sucked up through that front PCV valve, and going into your carb. I'd install a new 'Breather cap' on the valve cover (a filtered type V/C breather. your PCV valve need too "suck the 'vapors' , out of your engine.
Too do that , you use the PCV valve at the rear port , and, a breather (filter type breather) , where you have the (non-breather) cap installed .
The engine will then : Breathe (in at the front breather (freash air in) ; and your (rear) PCV valve (hooked up to the rear carb vac port . . . works to "evacuate inside your engine" .

breath - in ; evacuate - out . (it can - not do that , using two PCV valves) .

Generally, when you remove the (sealed) V/C oil cap ; you may feel inside your V/C ............ and , I'd bet there is NO baffel , inside the front small hole ....... thus, the front PCV valve is causing your "missing 1/2 qt of oil" .
I sure would also check that there is a baffel under the rear valve hole .
For my 250 engine - I think I use a 16lbs rad cap. I'd buy a new radiator cap . I am also using the OFFY 4bbl intake & my stock exhaust manifold ; with the Holley 390cfm carb. I also am using an "Oil Catch Can" , between my rear PCV valve , and my carb port.

later , jim

ps - - I am using the " DF - 17 " pcv valve by : M E Wagner .

Update, I drilled a hole in the front PCV valve so it will blow air either way and it’s connected to the air breather. It has stopped using much oil with 300 miles since new rebuild. After driving I can be at rest, speed the motor up and release the throttle . As it is almost back to idle a large puff of smoke comes out of the exhaust pipe. Rings not seated yet??

I'm not there but from picture it doesnt look like oil smoke. Keep exercising it and watch it. It just may get better.

How about a pic of your engine, crank case vent set up?

I believe my 250's had at least a 3/4" hose running from the valve cover to the air cleaner. Drilling a hole in the 2nd PVC might not be enough of a vent. After it's warmed up and idling take the PVC's out of the valve cover and checked to see how much fumes you have coming out. It's to early in the break in process to tell anything but for piece of mind I would do a compression check and write down the test numbers per cylinder. At least you would have starting point as you go thru the break in process.

There should only be one pcv valve, I think. I've never heard of an engine set up with two.

Have you checked the vacuum at the crankcase?
If you have a vacuum guage (cheap and good to have in your toolbox if you are working on pcv system):

-1st-take a vacuum reading at idle from your dipstick before doing anything, I would expect no readable vacuum.

-2nd- tape off the oil fill cap/air inlets and test vacuum again from the dipstick, expect 1-3 hg(edit) at idle. This will tell you if your pcv valve(s) is/are sized correctly. You also should feel vacuum build if you put your hand over the open oil fill hole on the valve cover. This is a system test, NOT an operating condition.

If you are not letting air into the crankcase…..you should, the contaminated air is not get evacuated if you are not letting unrestricted clean outside air in.
Typical is 3/8 tube from pvc valve to carb or intake vacuum port, 5/8” (or bigger) from clean side of air filter to valve cover (or a valve cover filtered breather type cap).
Not sure of your engine, does it have slits in the valve cover that want to be closed up?

I've never been able to measure vacuum in PSI- - - - -how is that done?
Jerry

Here you go Jerry.