Guys...need some help here.
BMF built (now out of business) my Mustang EFI motor (new rings, bearings and all seals) this last summer. Luckily they are still working with me on trying to find an oil leak with no luck. Valve cover gaskets were replaced which helped some. It's not dripping oil when parked but is losing about a 1/2 quart every 400-500 miles. There is always a bit of oil on the edge of the bellhousing which is blowing back (assuming) when driving and I'm getting a definite smell of burning oil when on the highway after 10-minutes or so of driving. Any ideas? Only have about 3000 miles on the motor since the build.

Thanks!

Rings didn't seat properly or were installed incorrectly.

If its leaking out the back while driving I bet its the end gasket on the intake manifold. did they use the gasket or just a bead of silicone?

could be valve guide seals , do a compression test or leak down and that will check the rings .

I have dealt with tons of oil leaks over the years. It could be anything from the rear main seal, rear cam plug, galley plugs, intake manifold, or anything else on the block that has an oil passage that can be directed towards your exhaust. I always ran an engine oil dye test with a black light to inspect for oil leaks before taking anything apart. If it can not be seen visually and was only at the rear then I pull trans to inspect rear main seal and cam plug. Sometimes I find the head plug in the back leaking also. Check the oil filter and oil pressure sender fittings as well, if its just a tad too loose (do not over tighten it either) it can be one of them pesky random leaks.

If it doesnt leak sitting still with the engine off....let it sit for a while running and see if you detect a leak that way.

Thanks for the ideas guys....will start checking them this weekend.

I told myself before bringing the Bronco out as my daily that all work would be done by myself or under my watch as I learn because "if you want it done right, do it your self"...thinking this engine swap is going to bite me in the butt/wallet.

Looked into some of the thoughts so far...

No smoke on start up or during idle, around town or on the highway so I'm ruling out the rings and valve guides.

Best way I have found to find an oil leak is wash the engine so no residue remains. Put some cardboard underneath it and start it up. With a flashlight handy start watching every inch of the motor until the leak is viewable. I would go with Zoso's idea about the intake manifold.

Wouldn't the a leak from the intake gasket result in a vacuum leak...the engine idle and runs well besides the oil leak...no mess on the engine besides at the very bottom of the bellhousing. Intake gasket would probably be the easiest to fix.

No. The only place the intake can leak oil is at the front and back seals. There should be just a little crankcase vacuum there at idle but you probably wouldn't notice a vac leak there.

The PCV valve and grommet is also a potential leak at the back of the intake.

Thanks for the quick response Phil...Will be checking the intake and pcv area before going for the rear main.

Don't see anything from the intake or pcv valve area.....I've read about a filter for the pcv, how important and where does it install?

It goes under the PCV grommet. It's supposed to prevent oil from being sucked up through the PCV valve and into the intake and burned.

Well, back from another trip from the guys that built the motor and he thinks it the PCV system creating too much crankcase pressure. He disconnected a few PCV lines and pluged the TB port....told me to watch it for two days and see if oil consumption goes down.

Any thoughts on the PCV system?

The PCV system needs to be closed on a mass air motor. That means a single PCV valve sucks gasses from the crankcase (below intake is considered crankcase) and the only fresh air that is allowed in is through a single line connected to air intake after it has passed through the MAF. No other breathers.

Now there may be an issue with the oil baffle on the bottom of the lower intake. That is supposed to keep oil from getting to the PCV valve. Some intakes used a very small baffle that didn't work very well. This causes oil to get drawn into the upper intake plenum. My intake was like this so I built a better baffle.

If the consumption isn't baffle related it has to be a poor seal at the rings or valve guides. A leakdown test will pinpoint the exact cause. A look at the spark plugs may narrow it down to the specific cylinder. The engine guys should have done this first.

Thanks Phil....I don't know if it's laziness or just lacking the knowledge with these guys anymore! It might be time to cut my lo$$es with them. This swap started last July and its less reliable than my old stock motor with 200k miles on it.

Is there a way to check/test the lower intake baffle?

Wouldn't bad rings or valve guides result in smoke from the exhaust?

Could it be that too much crank pressure is being developed?

Thanks as always!

The presence of blue smoke is dependant on where the oil is coming from. If it's rings the smoke would be present under load like starting off from a stop. Leaking valve seals/guides are likely to cause smoke when the engine vacuum is high like coasting down a hill. You may be able to see ring smoke from the driver's seat but probably can't see valve smoke.

Crankcase pressure is the result of blowby. Generally the PCV valve and intake vacuum can handle it. If the pressure is great enough it will force gasses backwards through the fresh air tube to get sucked into the throttle body. Crankcase pressure really shouldn't buildup to any great amount. If it does (plugged PCV and fresh air tube) oil will be pushed out the external engine seals/gaskets.

I don't know an easy way to test the baffle. What I did with mine was to reverse the airflow into the crankcase. Fresh air in at the PCV hole and PCV valve attached to the oil filler tube. That eliminated the oil in the upper intake. The next time I had the intake off I built a better baffle and put the PCV routing back to stock.

I've had friends drive behind me and under different situations...starting full throttle, starting half throttle, full throttle at highway spped, full throttle at 40mph, coasting downhill on highway and coasting downhill in town...

Do you have any detailed pics on your vacuum/pcv hose routing?

I don't. I had to rig it pretty good. I gutted a PCV valve to make a hose connection in the PCV hole and found a PCV valve with hose nipples on both ends. Then just routed fresh air into the original PCV hole and used the inline PCV valve from the oil filler. It was ugly but it worked.

Wanting to get a leak down test completed...any reccomendations up north, I'm in Greeley? Really wanting to get back to driving the Bronco again but the motor and EFI stuff is out of my skill set.

Can't you tell alot by looking at the plugs? My son is having issues with his newly rebuilt engine -- oil loss and blow by -- and he see it on his plugs pretty quickly. He has to chage out a couple on one or two cylinders every couple of hundred miles at most. Bad rings, yes?

Pulled plugs this last week to fix the header gasket leaks...plugs look good.