427 oil leak

[Mark65]

Hi, before I tear the pan off this side oiler to attack the rear main, I thought I'd post a couple of pictures of the oil leak that developed soon after I rebuilt it  a couple of years ago.  The leak may have got a little worse in that time but it was always pretty bad.  Since the rebuild it's done about 3000 miles.  I cleaned off the oil leaks then warmed up the engine but didn't drive the car.  After shutoff I took these pics of oil leaking down the midplate and my strong suspicion is it's the side seals.  The first picture was taken about 10 mins after shutoff where the streaks are about an inch to the outside of the side seals.  If the streaks had been directly under the side seals I'd have no doubt these were the sources.  As they're an inch away on both sides I'm less certain. The second picture was taken after about 90 mins where the oil paths have widened and started to coalesce near the top (difficult to see in the pics).  I wonder if anyone can confirm the side seals are most likely the problem.  I used the rubber seals with the nails provided and some RTV as I recall, but I didn't put any RTV under the main cap.  Neoprene rear main seal - no rope.  The intake manifold and rocker covers are not leaking.  Hopefully the pics have attached OK.
Thanks in advance, Mark

[Barry_R]

Could also be the rear galley plugs or the cam plug.
You might be able to sneak a bore scope in through the starter opening to see the back of the block...

[Autoholic]

I'd bet it's the infamous rear main leak.

[jayb]

I would also be concerned with the plugs at the back of the block.  Are you planning to fix it with the engine in the car, or will you pull it out, or pull the transmission back? 

Worst comes to worst, you could re-seal the rear main cap, and if it still leaks, at least you know its the plugs at the back of the block.

[Mark65]

I'll try to do it with the engine in the car.  The lifter galleries above the cam have not been drilled so I assume there's only the one gallery plugged under the cam, apart from the main gallery and relief plugs to the left.  Maybe try Barry's idea with a bore scope.  Such a pain as the engine runs so well!

[Phil0618]

I have had a similar looking leak and its coming from the intake seal. I would reseal that before pulling the block.

Phil

[cjshaker]

Sounds like it's a solid lifter block, so it's obviously not the galley plugs. An intake leak should be obvious by just wiping a finger across the back sealing ledge of the intake.

Those leaks are fairly wide of the main cap, which usually leaks straight down. My guess is it's the rear cam plug and it's migrating around the humps and valleys of the rear bulkhead before making its way out the bottom.

[Mark65]

Thanks to all for your help.  Yes, it's a solid lifter block.  It's definitely not the intake leaking - clean as a whistle at the back of the manifold. 

As the engine's in a Cobra it's impossible to get the bellhousing off with the engine in the car.  Thinking about it, because of the scattershield backing plate it may be impossible to see anything with a borescope through the starter hole.

Is it possible to do the rear main seals with the engine in place when you've got that Lakewood backing plate right up against the back of the block? 



 

[jayb]

Yes, you can do the rear main with the block plate in place.

[Mark65]

Just to update my investigations on the oil leak, I didn't run the engine for a couple of days then I wiped away all leaked oil from the lower rear of the engine.  I then jacked the front of the car and left it to stand over the weekend to see if oil would escape just by standing at an angle.  When I looked at it Monday the leaks had reappeared, same location as before.  Maybe a little less amount but very noticeable.  Does this mean it's definitely the rear main/side seals?  To make matters worse it looks difficult if not impossible to do this in situ.  The pan will come off but access to the RMS is badly hampered by the crossmember. 
Thanks
Mark

[Barry_R]

Either the engine or the trans is on its way out...