Thread: Question for our engine experts.

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I've had a little oil leak out of the rear main seal on the Ford 331 stroker in my 27 since the day I got it running the first time. It will even drip slightly just sitting in the garage overnight. This is a one piece seal. I thought I might have screwed up the first one, so I pulled the engine and took my time and put a new one in. Same thing, still drips a little.

While the engine is out this time I want to fix it properly and have spoken to Scat and FelPro. A guy at Scat told me he has heard of this and that Ford made two seals, one with an ID of 3.543 and another one with an ID of 3.493. He said to use the smaller one.

I have been going nuts trying to find one and finally did today at Summit.....it is on it's way. What do you guys think about this? Another guy I spoke with today at Scat says their crank is designed to work with the standard 3.543 seal. I just want to fix it properly this time.

Thanks guys,

Don

Buy more oil ???

Don

Its probably not the seal leaking unless----block has been align bored and the caps were cut severely

If you have the pan off, put a little dab of silicone on the ends of the main cap where they go over to the pan rail

Make sure its not a oil galley plug, camshaft freeze plug or even a leak from the manifold thats running down

A oil filter leak can run back along the pan rail and look like a rear seal

There also have been cases of high pressure/volume oil pumps spraying bypassed oil stream over to where the gasket wasn t sealed

In other words----good luck

I know you probably already did this Don.
But I would check the crank real good where the seal seats on it.
Maybe even take a buffer pad and try to polish it up a little.
You know to make sure there is no ridge's or anything stuck to
the crank like rubber from the old seal. It almost makes me wonder if
it ain't out of round or got a nick or something.
I did have a freind that installed his in back wards but he had more then just a drip now and then. Next are you sure it is not comming from up above and running down?
I know I have had oil senders leak down like that before.
Just asking, I know you probably checked all that stuff.
Good luck Don; Hope you get it fixed this time.
Kurt

Now now Steve,who's the card???? Hey Don,use that Ford for your boat anchor on your fishing boat and put a proper engine in it (Chevy)...

Originally Posted by Louey

After reading this carefully, the first thing I would do is get the mic out and do some checking. Is it really 3.543 or not ? Secondly, is the seal coming a double lip or single lip seal ? And of course, all the other things mentioned. Lots of could be's. I would just start with the mic, and check everything.

Using a mike may be your best bit but .050 smaller is not a lot as .025 a side. and if Ford made them for it why not use it????
An after thought --after changing the seal run the engine on a stand to see whats what.

my new 351 did the same...i built it, and it wasnt my first but sure enough....a drip one night....go a few, a drip....i used the small seal on a new scat crank with no line bore...i'm puttin money on the cap fit/one piece gasket not being happy....usually i just dib some sealer on both sides of the rear main cap in that crack btwn block and cap, then smoosh the tiddy on the gasket in....this time i didnt dib...now my shit leaks

I'll trade you - one C4 that has leaked since day one. I just keep a pan under it and promise myself that someday (soon!!) I'll pull that tranny and put my spare in its place. It's a long winter here in the normally frozen tundra of Upstate NY......

i dont have a clue .. my 351 leaks as well and iv`e built it a dozen times

Not being totally familiar with Ford, things you could check: some seals are directional-is it installed the right direction, is it leaking at the seal surface on crank or is it leaking between the seal and cap, how much difference should the seal and crank be in size-too much difference and the seal will not last. Just some food for thought.
Good luck Don.

I read one time that our hot rods are not leaking oil, they are marking their territory!

Thanks for all the suggestions, even yours, Steve. Yes, the block has been line bored and I took a magifying glass to look at the crank and seal once I had the flywheel off, and it is definitely leaking between the rubber seal and the journal of the crank where that seal rides. I wiped it and watched it seep again.

I took a good look at the back of the crank when I put the second seal in, cleaned it with a scotchbrite pad and then a clean rag. It looked fine to me. I don't own a good, accurate mike set, but I think I will buy one before this one goes back together. The seal that is in there now is a double seal, if I recall, and the new one coming is from FelPros Performance line.......it should be good, it was $ 45 for that one seal!!! I am also going to put a little silicone around the outside of the seal when I install it, just for giggles, but it seems dry there.

The line bore thing makes sense because I had to go to a shorter timing chain because the stock one was a little sloppy. And, the seepage is on the bottom of the journal, as if the crank were sitting a little high in the block. It only leaks a slight amount, but I sure would like to cure it while the engine is out again.

Thanks again for all the help guys, and yes Steve, I will buy lots of oil.

Don

maybe it's just me but I haven't seen many ford engines that don't seep a lil at the rear main.

Originally Posted by DeepRoots

maybe it's just me but I haven't seen many ford engines that don't seep a lil at the rear main.

??? Not since the 'Y' block. They were tough to keep dry with that rope seal and those two little side seals plus that exterior oil pump pickup tube
The new ones - not mine anyhow.
Trannys - my current C4, yes

Rear seal leaki ng after a good attempt to fix? It isn't like you don't know what you're looking at, i bet the seal isn't where it is leaking from. How can it leak from the seal when it is (presumabably) sitting level in your garage - you don't have enough oil in the pan to leak out of the rear seal - if the car is on a steep incline i can see a reason to leak. The only way it'll leak out of the rear seal while sitting level and the engine not running is to have the oil in the pan up as high as the seal - but then the engine would barely crank over since the crank would have to wade thru oil.
Can you mock it up on the stand for a looksee? If it is still together can you add air pressure in place of the pcv valve and see where the oil pops up? Not much pressure or you'll be replacing the front main seal too. Just a thought, good luck oj

The engine in my 27 sits on a higher than normal tilt toward the rear, so the oil level is probably at least at the height where it could seep out of that spot. When I replaced the first seal I examined it very closely, as I did the second time. I was expecting to see the oil seeping from around the outside circumferance of the seal because that is metal to metal (metal seal body to metal rear bearing cap) But it is totally dry there. But there was wetness around the bottom of the rubber part where it rides on the crank journal.

Further, I took a magifying glass and really examined that area and the top of the seal is fairly dry, but the bottom showed the wetness. I wiped it totally dry, even using some lacquer thinner, and after a few minutes the wetness reappeared in that same lower place on the journal. No question in my mind it is the rubber to journal seal that is not holding.

You can see in this picture the tilt my engine sits on, and how the oil level could be over that spot on the back of the crank. It actually looks more level in this picture than it really is.......it tilts down quite a bit in reality because this picture was taken before the first ride. Once I let the clutch out, the back sat down a couple more inches than here.

Don