Major leak issue with new engine install, need any and all help guys

[UATahoe]

Ok, finished up installing the 383 in my 87. Started it up 3 times now in the garage. Hasn't been driven. Would let it idle and get up to temp and then shut it down. Checked it over for leaks and all was well. Decided to back it out of the garage and let it run again this evening. My driveway is on a pretty good incline to get into the garage. Let it run up to 180 degrees and then shutter down. Once I turned it off some type of fluid was leaking very steadily down the Flexplate. Looked like it could have possibly been coming from the rear seal. A picture of the fluid is below. What is puzzling is it seems to have a very strong gas smell to it. Didn't want to start it up again so got a lot of help to push it back in to the garage. Once it was on level ground, the leak quit immediately. I am totally puzzled on this one and fearing the worst here. Have no idea what could be going on.
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[79Betty]

Could be rear main but could be anything in the back of motor. Better grab a good light and look closer before driving it more.
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[UATahoe]

Yep, it's parked indefinitely. Sad thing is it is a brand new motor and overhauled tranny that have never been driven. Backing out of the garage this evening was the first movement it has seen. What could be the reason for the strong gas odor? Gas in the oil seems like a really severe problem.
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[79Betty]

I don't know can be many things. I once bought a 350 from jegs the 290 hp one if i remember right. Looked it over put it in fired it up and leaked like a siv from back of motor on top. Turns out it didn't have the back intake gasket installed at all.
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[UATahoe]

What a freakin headache. I am also baffled that it only leaks on an incline. On level ground it is fine.
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[mgchevyparts]

Gas in the oil is usually from flooding carb or very rich mixture. You can get lots of gas in the oil if you had been cranking the engine a lot. You can wash the rings out if the oil is gas diluted. Check if the carb is flooding over. You need to change the oil. Of course you need to figure out why the oil is leaking out the back.

[UATahoe]

It's a fuel injected motor with the stock style tbi
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[UATahoe]

Checked the back of the motor. No fluid on the back of the heads, no fluid around the distributor, none around the oil pressure sensor right next to the distributor. Can't find any fluid on the top side.
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[mud.man.rj]

I have seen the crank seals installed in backwards on the split seal type and really leaks bad, not sure if yours in a 1 piece seal or not, depends on year, if it is 1 piece then not that for sure. Could be an oil plug at the back of block which are close to the cam plug at the back of engine. Crossing my fingers it is an easy fix, but sure is a lot of oil.

[UATahoe]

Oh and the jar was the small amount. The majority was in my driveway. Triple the jar and that was what was in the driveway. Would say at least half a court of fluid for sure. But here is the strange thing. Checked the dipstick, oil still showed right at full and was very clean. And it's a one piece rear seal
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[MusicMan70]

How about jacking up the front end to see if you can duplicate the "incline" and see if that points you in the direction of the leak?!

[UATahoe]

That's definitely the plan for tomorrow. Jack is already in place. Lol.
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[mgchevyparts]

Originally Posted by UATahoe

It's a fuel injected motor with the stock style tbi
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Don't start it again without first changing the oil. Washing out the rings means you have little to no lubrication and the rings will wear and you will need to re-ring at least.

[UATahoe]

Man it's a brand new motor. You saying you think it needs to be torn down and re-ringed? Sounds like the engine builder will need to make it right to me.
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[bigwheel15]

Originally Posted by UATahoe

Man it's a brand new motor. You saying you think it needs to be torn down and re-ringed? Sounds like the engine builder will need to make it right to me.
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What he saying is if you were to continue to run it with gas in the oil you'd likely wash out the rings, not that that is what happened already.

[BigBlocksRule]

When you check the rear main seal - sounds like that's the culprit - you'll need to move the tranny back. Get some all-thread and cut a couple of pieces about a foot long, thread a nut on one end. Replace two of the tranny bolts - one on each side - with these. Then remove the rest of the tranny bolts. Use a jack to hold the tranny up and you can slide the whole thing back and out of the way and you won't have to fight it trying to realign everything.
Have a new seal in hand and get the gasket that goes between the block and rear main seal fixture, those will leak sometimes.
It leaks on an incline because that's when the oil level is up to the incorrectly installed or defective rear main seal. Double check the pan gasket in the back, too.

[UATahoe]

Thanks guys for the input. I do believe it is the rear main seal. I am going to check this afternoon since the truck has cooled down now. It looked like it was running out from the very rear of the oil pan which is what lead me to believe the rear seal was the culprit. The only thing i cant understand is the strong gas smell. Plus, i checked the dipstick and it was still reading full and the oil looked brand new. I did have a lot of gas leak issues with the throttlebody at the pressure regulator. The gasket was bunched and i had to tear it down and reinstall it right. After that no gas leak at all. Maybe the gas that ran out had puddled somewhere and finally made its way out when it was inclined? This is a tough one. Also cant figure out the color.

[tony58]

Originally Posted by UATahoe

Man it's a brand new motor. You saying you think it needs to be torn down and re-ringed? Sounds like the engine builder will need to make it right to me.
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If you ran it with diluted oil the repair would be on you not the builder. The builder has nothing to do with your fuel problems.

[UATahoe]

Just meant if the rear seal is leaking. Thats all.

[UATahoe]

I am really starting to think it may have been fuel that had puddled up in the bellhousing. The fuel leak i had was substantial and actually covered the top manifold with fuel. And we didnt notice it with the air filter on until after trying to crank it a good many times. I am thinking a good majority of that ran down the back of the motor and into the bellhousing. The motor is painted with grey engine paint on top of a cranberry color paint. Thinking the gas ate away at some of the paint giving it the really strange color. None of the dipsticks show low fluid levels. I am going to jack it up this afternoon to see if anything else leaks out.

[88Jimmy4x4]

drive it around the block come back see if it leaks

[slugish]

been chasing oil leaks for months now . Finally took it to an old gear head whos been fooling with stuff like this all his life .

After redoing my oil pan gasket , timing cover , replacing my oil pressure sending unit -> still leaked >took it back to him said hes almost sure the oil leak that's running down the passenger side of the engine is coming from the mechanical fuel pump . Said , he has seen this before , but usually its gas that is coming out of ,or around the fuel pump / .

Hope this helps , know how frustrating this can get ..

[rs74]

As I was reading down the replies I kept thinking to myself that I thought you have had issues getting this engine lined out for awhile. Then you brought up the fuel regulator issue. The whole time you were messing with that there have been a bunch of fuel dumped down in the engine? If you were squirting fuel down the TB and it not firing then you will eventually get some buildup of fuel in the oil. Unless I am missing something here I am sure that is why you have fuel in the oil.

If you had fuel on the back of the block I would think that most of it would have evaporated by the time you got around to firing it up. Yes it does sound like a rear main seal that is bad. I would be draining the oil and putting a new filter in for peace of mind. JMO.

[UATahoe]

I actually only got around to trying to fire it up about a week ago. Tried a lot and with the pressure regulator seal being bad it definitely dumped out a lot of gas every time we turned the key on. Didn't get a chance to check it our tonight but will try to tomorrow. I am going to jack it up and see if any more fluid leaks out. Checked under it in the garage and not a single drip. Crossing my fingers that it was just fuel puddled up somewhere. We shall see. Trying to stay positive. Lol.
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[UATahoe]

Will definitely be changing out the oil and filter though.
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