yamban

Hey folks. Last week I noticed that I had a small dot of oil underneath the Z28. I also noticed that the car would idle at 1000-1100RPM after it was warmed up... 700-800RPM when cold. The motor is a carbed (no choke) 69 block fully rebuilt with about 7000-9000KM's with about 350hp. Today I went out to see dot about the size of a quarter and I could see that it that the oil came from between the tranny and engine. About a month ago I had to replace the PCV valve because it was not functioning properly, my car would stall periodically when accelerating. Problem solved with a new valve.

To me it seems possible that the valve is getting stuck closed/partially closed and its putting the crank case under more pressure then it should, causing it to leak. Is this possible? It just seems weird that the high idle when hot/ oil leak happened around the same time. I can't see it needing a new rear main seal already, but you never know. I checked for vacuum leaks and if anything the PCV needs a new grommet. Tomorrow I am going to buy that and 1-2 new valves to see if that helps the idle... is there anything else that anyone has experience with the problems Im having?

Thanks alot for any input.

fyrebird68

iTrader: (1)

I follow your thinking but I don't believe that the motor could generate enough crankcase pressure to push through the rear main. Even for a worn-out old motor that would be some big-time blow-by.

You don't mention how old the motor rebuild is. More likely the rear main seal is worn or has a problem. If it's new(er) maybe there was a nick in the seal or not fully seated when installed.

yamban

Hmm the engine was rebuilt in 2009. I did not do the work so I cannot vouch for the main seal in any condition. I would just think they replaced it, but even so I guess many variable could come into play. My oil pressure is around 60PSI cold, maybe I got a little heavy footed during the cold the past week or two and that pushed a little oil through. Im not sure what kind of pressure an intact seal can hold. Hopefully this week I can get around to taking a look inside.

fyrebird68

iTrader: (1)

If the crankcase pressure WAS causing the problem, you should see the leak go away when you changed the PCV valve.