cant stop this oil leak -long-

[81GrandPrix383]

Hey,
I built this 383 hoping to get the car on the road this past summer but my lack of free time and Honey-Do list have me way behind schedule and we have already had snow here in Central Ontario so realistically I cant see this car leaving my garage until the spring.
The biggest challenge has been trying to stop this oil leak so I wanted to throw what I know at you all to see if anyone has experienced anything similar.

First assembly I used a cheap polished aluminum pan and figured it wasn't sealing properly so I picked up a Moroso pan that was in a clearance bin and used it for the second assembly with a new fel-pro reusable gasket and permatex the right stuff all the way around. After removal and closer inspection the back of the pan seemed like it was out of round. We tried to reshape the pan and re-used the gasket with lots of the right stuff this time. Both times the stuff was spread all the way around not just in the corners.
Still leaking and when I say leaking i mean spraying oil. In ten minutes of running it left a quart of oil on my garage floor.
4th assembly with a brand new moroso pan and a brand new Fel-Pro 1-pc rubber gasket and Permatex Copper in the corners only and a new rear main seal and the thing still leaks.

My engine builder who assembled my short block and I are at a loss.
The plan is to pull the transmission and the flexplate and start the car with someone under it watching.
Until then I thought i would see what people think.

A couple of people have suggested that i may have excessive crank case pressure with the rings not being set yet which is blowing oil out the rear main seal. i have a pcv valve on one cover and an open breather on the other.

Thanks in advance for any comments.
Ill see if i can post some pictures for those who would like to see the car.

 

[81GrandPrix383]

 

[chevy2480]

Are you sure its not the rear main seal? To lose that much oil that quick i am betting its not the pan and is the rear main seal. Remove the breathers from both valve cover that will allow any crankcase pressure to leave. Then see if it still leaks i am almost sure it will. It is possible that builder could have torn or put seal in backwards even the best make mistakes. To have done the pan as many times you have and still leak would make me believe it not the pan.

And also you cant start the car with flexplate removed. Take a flashlight and see if oil is coming from up high if so oil gallery plugs could be leaking.

 

[LSCustoms]

Y did you replace the pan? did you see it leaking from there too.. can you see where the oil is leaking from? have you checked the oil pressure sender, or around the back of the intake? sometimes when you use a gasket on that it leaks and you have to use gasket maker on the front and back of the intake... anyhow, i hope its something simple

 

[GhettoRacingKid]

its the rear main dude... thats the only time ive seen it "spray" out

ive had a few oil leaks in my day

 

[beermonkey9417]

how long are you letting the gasket set up? i had this problem with my trans, i d replace the gasket and use gasket sealer and the i would try and fill it up and it would leak, then one day after just replacing the gasket and letting it set over night it held fluid without leaking.

 

[81GrandPrix383]

Are you sure its not the rear main seal? To lose that much oil that quick i am betting its not the pan and is the rear main seal. Remove the breathers from both valve cover that will allow any crankcase pressure to leave. Then see if it still leaks i am almost sure it will. It is possible that builder could have torn or put seal in backwards even the best make mistakes. To have done the pan as many times you have and still leak would make me believe it not the pan.

And also you cant start the car with flexplate removed. Take a flashlight and see if oil is coming from up high if so oil gallery plugs could be leaking.

Thanks Chevy2480,

I'm not sure it isnt the rear main seal but we already replaced it once and it is still leaking. only ran the car for 30 seconds and there was already a puddle and oil dripping off everything.
The one we took out looked fine.
I was thinking oil galley plugs thats what I wanted to see with the flexplate out. plus the camshaft plug.
I have lots of oil pressure, around 80lbs at 3000rpms last time I checked.
Thanks for the tip about the flexplate. I`m pretty sure I would have figured that out when I got under the car and saw the starter....pretty sure. lol.

 

[81GrandPrix383]

Y did you replace the pan? did you see it leaking from there too.. can you see where the oil is leaking from? have you checked the oil pressure sender, or around the back of the intake? sometimes when you use a gasket on that it leaks and you have to use gasket maker on the front and back of the intake... anyhow, i hope its something simple

Thanks LSCustoms

Builder put the pan on originally. Originally thought the leak had to be the pan as he said he had never had a rear main seal leak in his 16 years of building race motors. When we test fit it to put it back on it did not sit right and rocked. I said `F`it and changed it.
Havent been under the car when leaking. That is next I guess. The oil is hitting the flexplate and spraying all over.
Back of the intake and pressure sender are dry. 100% not from there.

 

[81GrandPrix383]

its the rear main dude... thats the only time ive seen it "spray" out

ive had a few oil leaks in my day

I hear you GhettoRacingKid but we changed the rear main seal once already.
For it to leak twice in a row after being installed by my builder who claims he has never had one leak....

Seems a little odd, unless there is a flaw in the crank that no one noticed or my crankcase pressure is so high that a perfectly installed seal would still be leaking.

 

[81GrandPrix383]

how long are you letting the gasket set up? i had this problem with my trans, i d replace the gasket and use gasket sealer and the i would try and fill it up and it would leak, then one day after just replacing the gasket and letting it set over night it held fluid without leaking.

Hey BeerMonkey,

The most recent time it set for a week before I put any oil in the motor.