318 LA rear main leak?

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after you take it apart and even if you do find out what is muffed put it back together without the seal and show us a pic of what the gap looks like naked
thanks
 
There usually is a gap on the sides so the the bearing face touches home before the sides so you get the right amount of crush on the rear main & it doesn't get hung up on the side face.
Usually i check with a plastigauge around .023
I use the Felpro BS 40245 or the double lip super seal from Mancini .
There is also the problem if any oil comes from the top valley plate or rear of the rocker covers the oil runs down the back of the engine & comes out the same place a leaking rear main does.
I doubt weather spinning the oil pump will help as most of the rear main leakage comes from when you take off & oil in the sump splashes on the rear main seal & when braking it splashes on the front seal
Also check you have a pipe hooked up to rocker cover via the PVC valve from the vacuum it helps to create a slight vacuum in the engine to help with leakage some guys put 1 to both rocker covers
 
Your rear main does not look correct in the photos but having said that there is a lot of places oil can come from but still looks like a rear main leak. I kept thinking my leak was from the oil filter plate. (in Aus we run a remote filter set up)I found the oil sender unit had been tightened up too much and cracked the block. This was fixed by some cold weld material but had a persistent oil leak comming down near the oil lines but found the alloy rocker covers not to have clearance at the inlet manifold ports but the oil tracks down to the bottom in weird places. Had to clearance the rocker covers but now is all good. Just get a bit of oil on the rear of the sump after about a couple thousand kays and I can live with that( just a clean rag wipe and all is good.)
 
My 318 LA is on the stand, its a tight gap.
 
I thought mine was leaking but turned out to be the Cam plug. I tapped it in in with sealant but didn't know you had to hit the middle with a socket to expand it. Hope you figure it out. Good luck.
 
AUSA66 said:
There usually is a gap on the sides so the the bearing face touches home before the sides so you get the right amount of crush on the rear main & it doesn't get hung up on the side face.
Usually i check with a plastigauge around .023
I use the Felpro BS 40245 or the double lip super seal from Mancini .
There is also the problem if any oil comes from the top valley plate or rear of the rocker covers the oil runs down the back of the engine & comes out the same place a leaking rear main does.
I doubt weather spinning the oil pump will help as most of the rear main leakage comes from when you take off & oil in the sump splashes on the rear main seal & when braking it splashes on the front seal
Also check you have a pipe hooked up to rocker cover via the PVC valve from the vacuum it helps to create a slight vacuum in the engine to help with leakage some guys put 1 to both rocker covers
Click to expand...
Tooljunkie said:
My 318 LA is on the stand, its a tight gap.[/QUOT


Ok so I pulled the sump tonight & removed the rear main cap all looked ok
I removed the lower seal & fitted the main cap with tight bolts & same gap was apparent.
then I removed the top seal & rear cap bearing shell & refitted & same thing I have a gap.
then I checked the rear cap with a straight edge after removing again to find that it looks flat to me & it should sit flush on the block.
Here are some pics
Click to expand...

20190702_194144.jpg
 
Ok so I pulled the sump tonight & removed the rear main cap all looked ok
I removed the lower seal & fitted the main cap with tight bolts & same gap was apparent.
then I removed the top seal & rear cap bearing shell & refitted & same thing I have a gap.
then I checked the rear cap with a straight edge after removing again to find that it looks flat to me & it should sit flush on the block.
Here are some pics
 
Take your camera and angle it in behind the crank flange. That surface in the picture is not the cap mating surface. Red arrow is the area you are taking a picture of, black arrow is where you should be taking a picture of and is the area that matters.

BB46BFBF-8407-4DD3-9F2B-DD739921AC68.jpeg
 
Kendog 170 said:
I thought mine was leaking but turned out to be the Cam plug. I tapped it in in with sealant but didn't know you had to hit the middle with a socket to expand it. Hope you figure it out. Good luck.
Click to expand...
Yep

100_5151.JPG
 
Wyrmrider said:
after you take it apart and even if you do find out what is muffed put it back together without the seal and show us a pic of what the gap looks like naked
thanks
Click to expand...

Thanks! I'm interested in that too!
 
furrystump said:
Take your camera and angle it in behind the crank flange. That surface in the picture is not the cap mating surface. Red arrow is the area you are taking a picture of, black arrow is where you should be taking a picture of and is the area that matters.

View attachment 1715357776
Click to expand...

....and that's the gap I have been talkin about. In his original picture, "it ain't right", IMO.
 
RustyRatRod said:
I agree it is, but nowhere near as prevalent.
Click to expand...




The gap on the side of the cap is there as it should be but the rear of the cap should sit hard on the block surface , but it sits up alittle with no seal & 1/2 bearing in
so i need to find out why this is. i can see witness marks from the wings so there is contact there.

20190702_193120.jpg
 
Do you have a pic of the bearing if was hanging up on the bearing it would seize if it was too loose you would have low oil pressure the bearing wear marks should tell a story
 
Also try cutting 2 lengths of drink straw 1 on each side of the inner mating surface then tension the cap remove it will show the contact area
 
Yall are going to think I am crazy........and shut up.......but I have never in my life seen the recesses in a small block main cap for those wings to go like that. Never. All of them I have ever seen and or put together like this were flat on that surface and had a standard rear main seal with no wings. This is new to me. .......and I've torn apart and assembled a lot of small blocks. I wouldn't like this. To me it's one more place to have a leak or some other problem.
 
Maybe different on different years i have 5 340 SB all have the wings see pic 1 is vintage rope seal for 340 the other is current wing seal all my blocks are 69 or 70 looks like there was a change somewhere 360 do not have the wings

rearmain1.jpg
rearmain.jpg
 
RustyRatRod said:
Yall are going to think I am crazy........and shut up.......but I have never in my life seen the recesses in a small block main cap for those wings to go like that. Never. All of them I have ever seen and or put together like this were flat on that surface and had a standard rear main seal with no wings. This is new to me. .......and I've torn apart and assembled a lot of small blocks. I wouldn't like this. To me it's one more place to have a leak or some other problem.
Click to expand...
Strange that the 70 dodge manual on the 318 to 340 doesn't mention wings it says to cut the upper & lower seal flush with the cap must have been the change from rope to rubber
 
AUSA66 said:
Strange that the 70 dodge manual on the 318 to 340 doesn't mention wings it says to cut the upper & lower seal flush with the cap must have been the change from rope to rubber
Click to expand...

Nobody else has really chimed in on it but I wonder if this is an Australia thing?
 
I have seen those wings in gasket sets many times but don't remember ever seeing a main cap that accepts them.
Went out to garage and checked a 340 block I have sitting here and, sure enough, it appears to have the channels in the cap for those darn wings.
I slid paper under the gap and you may be able to make out the channel.
IMG_20190701_194411.jpg
 
Bobzilla said:
I have seen those wings in gasket sets many times but don't remember ever seeing a main cap that accepts them.
Went out to garage and checked a 340 block I have sitting here and, sure enough, it appears to have the channels in the cap for those darn wings.
I slid paper under the gap and you may be able to make out the channel.View attachment 1715358053
Click to expand...

ok when the cap is tightened down do you have a gap between the cap and block beside the seal looking from the rear, seal or no seal fitted?
 
Thanks for the pics sure helps don't it
I never (remember) saw wings on older motors maybe a later thing
but then I forget lots
 
Bobzilla said:
I have seen those wings in gasket sets many times but don't remember ever seeing a main cap that accepts them.
Went out to garage and checked a 340 block I have sitting here and, sure enough, it appears to have the channels in the cap for those darn wings.
I slid paper under the gap and you may be able to make out the channel.View attachment 1715358053
Click to expand...



Ok so when it was torqued down you slid the paper under?
that's the same as mine then
 
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