Five rear mains later, could it be a crankshaft issue?

lovemycbx · Post by **lovemycbx** » Wed Jan 27, 2021 8:31 pm

Hey everyone, I decided to reach out after being on the verge of getting rid of the FE for a 460 in my 71 4WD highboy. I've been slowly upgrading and putting every once of love I have in to the truck since I pulled it out of a barn 4 years ago and I need some advice. I've replaced the tired and rusted .060 over 360 boat anchor block with a factory std to .030 over block with new cobra jet heads, remanufactured 390 crank and rods, pro flo 4 efi, roller rockers, machined and balanced treasure. Problem is no matter what I do a considerable amount of oil leaks from the rear main since rebuild. I've installed once, broke in the cam, saw a puddle of oil... pulled the engine... new rear main and reinstalled. Test drive.... drips of oil off the rear of the engine turning in to a puddle. Drove around to enjoy the new motor a bit. Got tired of the massive oil leak and pulled the pan off with engine in the truck two more times, two more seals, two more leaks. Finally pulled the trans for better access, new rear main, reassembled.... still leaks. At this point I'm suspecting that the issue is with the crank itself. I've heard of there being "marine" cranks with the grooves on the back of the crank pulling oil out of the block instead of back in but I'm suspecting it may be that when the crank I have was re-manufactured it was just honed down a bit too much and the new rear main just doesn't make a good seal.At this point I am damn near depressed and considering going with a new stroker 418 kit all new bearings, rods, pistons, and shiny new steel crankshaft to hopefully finally get the damn thing to stop leaking or just giving up on the FE and going to a 460.

Am I being completely unreasonable? Could it be the crankshaft causing me all the heartache? Any advice is appreciated, Thank you for reading,
-Ryan

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cep62 · Post by **cep62** » Wed Jan 27, 2021 9:45 pm

Make sure it's not leaking from the back of the intake .
FEs have a bad habit of this.
Oil dye and a black light can pinpoint a trail.

two-bit · Post by **two-bit** » Thu Jan 28, 2021 6:42 am

Its hard not being there to see it directly. I had an FE that i swore for sure had a bad rear main seal. Turned out it was the press in plug at the back of the cam bore.
I dropped the trans, the flywheel/clutch combo, then pulled the dizzy. Ran the oil pump with a drill, to get some oil pressure and found it. The plug was solid, just leaking around the edges of it. Replaced it, and TADA ! issue gone.
IF the shop that built your engine DID NOT put sealer on that cam bore plug, it maybe a very good chance thats where its coming from.
Maybe you problem ?
It was leaking a quart of oil every 50-60 miles, and left some pretty decent sized puddles.

Two-bit

Post by **DuckRyder** » Thu Jan 28, 2021 9:39 am

what are you doing with the side seals each time? are you offsetting the lip seal?

Agree with verifying it is actually the rear main and not intake, VC, cam plug or gallery plugs...

Nice looking motor...

davelj · Post by **davelj** » Thu Jan 28, 2021 3:08 pm

Multiple issues with oil leaks on the rear of an FE. The cam plug installs backwards to all others with the cup facing into the block, flat side out. Installed the wrong way and it can leak. The cam can even rub a hole in it if it's in backwards.

Rear of the intake. Those heavy suckers can be a real problem to seal. No only will they leak at the corners of the block face, but they can leak from the valve covers if the head and intake surfaces are too different in height. Often a problem if the heads have been milled.

If it is the rear main seal and you are using a rubber one and the crank is undersize on the seal surface, you can use a rope seal. It can be packed in to tighten it. The rubber type is directional and can be installed facing the wrong way, too. I have also seen a crank that the oil grooves on the sealing surface were deeper than normal and a rubber seal would not hold but a rope seal fixed that one. The rope type has a wider sealing surface. The two fiber seals that seal the cap to the block can also leak.

They have a pressurized feed to the rockers that runs through the head gasket that can occasionally leak. It is less likely than some of the others, though.

lovemycbx · Post by **lovemycbx** » Sun Jan 31, 2021 11:31 am

Took a couple of days to get a day without rain so I could get pictures and It looks like there is a three pic limit so I've tried to pick only the most telling ones but thank you all for the quick replies. So in response, the most recent seal I removed the trans to check the oil galleys and the cam cap for leakage and provided a pic. The image makes it look worse than it is because the way the block paint cured there is funny and it makes it look wet but it was dry on inspection with no obvious signs of oil pouring out of it. I've went from the factory cast manifold, to a performer, to the pro flo 4 and in the swaps learned pretty well how to get em sealed up alright and although there is a bit of residual oil from a bad sealing set of valve covers remaining on the edge of the head gasket, I just installed this new set of VC's and they look to be sealing great. I tried like hell to get a rope seal in to place when I did the last one also but after soaking the seal there was just no way to compress it in to the cap without it just looking like I had the totally wrong rope seal and it was about to cause significant clearance issues or damage on reinstall so I went with another rubber felpro seal. On rubber seal install I always offset the sealing lip about 1/4"-1/2" and the last one I decided against the side seals after trying them with/without rtv and this time went with filling the channels completely with silicone opting out of the nails which never left me feeling very good. On initial startup before installing the trans it looked to be a perfect seal running from cold to operating temp twice with no leaks whatsoever. After installing a new flywheel and upgraded Mcleoud clutch and the NP 435 back on I went for a test drive only to come back with the leak in full oil blasting, driveshaft covering, puddle making, sadness inducing glory. At this point with my pics I'm pretty sure that this crank needs to go. The bell housing is wet with oil slung inside it and I couldn't see any obvious signs of the common place leaks. Here are some pictures....

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lovemycbx · Post by **lovemycbx** » Sun Jan 31, 2021 11:35 am

A few more pictures

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lovemycbx · Post by **lovemycbx** » Sun Jan 31, 2021 11:38 am

and close ups on the block corners trying to verify the leak wasn't coming from above running down....

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davelj · Post by **davelj** » Mon Feb 01, 2021 2:10 pm

Any chance it is gear oil from the trans instead, maybe overfilled?

cbwheels · Post by **cbwheels** » Tue Feb 02, 2021 11:25 am

Been staring at your pictures and feeling your pain. From the pics it appears that the back of the intake manifold may be good, can't really see any pictures that show the aft valve cover area. Someone has already mentioned the possible difference in heights of the intake vs head where the vc seals. Good potential there.

You mentioned you left out the side seals on the rear cap and used silicone? I'd be a bit concerned about that area. Those side seals are not very installer friendly. I am just finishing a full build and installation on a replacement 390. The first side seals that I installed (on a stand) didn't go well. The nail installation was frustrating and just didn't feel right. It felt like they had not gone straight. Sure enough, pulled it apart and one nail swerved and poked the seal. Installed a new set and felt good. Went with a tip and built up a little RTV along the inside wall of cap to block surface after torqueing down. can't imagine doing it upside down. I could imagine that the RTV, especially depending on which type, did not completely fill the sides, or gave way.

My old tired 360 had a few good things going for it. It leaked so much that it preserved the underside of my CA truck very well! It definitely had a long term rear intake manifold leak, plus valve cover leaks. Replaced all those and was good until the rear main puked. Good reason to do the much needed upgrade. After the rebuild I was lucky enough to be able to break it in on a run stand and check closely for any leaks before installing it.

lovemycbx · Post by **lovemycbx** » Tue Feb 02, 2021 4:01 pm

The pain is real haha. There certainly was a valve cover leak on the old set and you can see the evidence of the old leak in this pic. The new VC set have looked to have made an excellent seals though. I was really hoping that was the main source of the leak but it didn't look to be the case. I made a elongated hose to fill the side seal channels with "The right stuff" via a caulking gun and watched the channels fill as I had the trans out for better access to the seal with the motor in the truck. I had done every way besides that and it looked to have worked perfectly until the test drive plus it was a method a hand full of FE builders had suggested so I figured why not. As far as it being the trans overfilled, I wish it was. It would somehow have to have been filled with about 25 gallons of oil at this point though

It's also pretty easy to identify the oil via the smell/color/amount and dipstick level but I have verified that with checking the trans level to be sure.

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lovemycbx · Post by **lovemycbx** » Tue Feb 02, 2021 4:10 pm

What really added some sting to the situation is I just finished up with my F600 instrument panel so I get to watch my oil pressure start to fall with the loss in real time.

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two-bit · Post by **two-bit** » Wed Feb 10, 2021 9:40 pm

So....
No closer to finding the problem than before ?
I have a few FE builds coming up and am kinda curious. In case i run across this, what the most viable solution may be.
Thanks
Two-bit

lovemycbx · Post by **lovemycbx** » Sat Feb 13, 2021 7:14 pm

After seeing the part number in another forum, I am 95% sure I've got a reverse rotation marine crank that's causing the problem. The grooves on the crank are pulling oil out of the seal and all over the road, trans, driveshaft, and entire underside of the truck. I'm about to fix it by replacing the crank with a stroker 445 crank kit. That way, at least if it doesn't fix the issue I'll have LOTS of fun blasting oil everywhere. As far as your upcoming FE builds just make sure your crank is not stamped with C6JE-J as it indicates it is for a reverse rotation marine application. That and follow the recommended oil mods to the block while you're there. They aren't too difficult and help adequate oiling.

jzjames · Post by **jzjames** » Sat Feb 13, 2021 10:01 pm

I knew you’d find the answer to this. This has been interesting at least.

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Five rear mains later, could it be a crankshaft issue?

Five rear mains later, could it be a crankshaft issue?

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Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

Re: Five rear mains later, could it be a crankshaft issue?

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Re: Five rear mains later, could it be a crankshaft issue?