I have a 1976 ford F-250 with a 390 that is blowing oil out of the dip-stick When I first start the truck I have about 70-75 lbs of oil preasure after it warms up it sits about 20-25 lbs any thoughts as to what might be causing this

 

you could be way over on the oil capacity. do you have a breather and a pcv installed?

 

I just changed the oil and if I pull the breather it still blows it out

 

how many quarts of oil? should be 5.5 with filter

 

I do believe you have a hole in one of your pistons.

 

My book and dip stick buth say 6 quarts

 

I did a compresion test and I am getting preasure on all of them I guess I will find out I am going to pull the heads tomorow and check them and the head gaskets

 

What does the compression tester read? I had this same problem on my 460 and it turned out to be bad rings. I was still getting 70-90 spi on a compression test, but that shound be up around 135-145. Not sure what yours should be.

Take a look in the engine forum on this site for your specific engine, and search for oil blow by. I know there are several posts in the 460 section on it.

Kevin K.

 

Sounds to me like the CCV system is plugged.

Pressure build-up in the crankcase without anywhere to go but out the dipstick tube.

Clean out the cap and CCV valve.

 

Might be a Pvc vavle pluged up. I know it did that to mine.

Edberg

 

Any body know what the compression should be on a 79 ford f-250 351M? im going to check them tommorow.

ohh and id say you have to much oil in your engine. i had that happen to me on a differnet truck.
thanks
mitch

 

This is not an over full oil level problem. It is either excessive blow by (caused by bad rings,pistons, cylinder walls, bad pcv system or any combination of these could be occurring at the same time.

On an extremely worn engine blow by has been seen through exhaust valve stem guides as well, but this is very rare.

 

thanks it was worn piston rings I am rebuilding the engine

 

Holy old thread!!!

Thanks for the update.

 

Was that in 2005,2006,or just recently in 2007 that you fixed it ?