someone gave me a 390. it was left out in the rain for who know how long. but anyway as i getting the engine freed up. i measured the bore and it read 4.06" with .030 stamped on the pistons. is this engine basically a 360?

i orginally took the engine cuz i needed a new crank for my 390, seeing the hash marks in the rear main seal area. leaks like there is no tomorrow.

 

The 360 & 390 use the same blocks with the same size bores. A .030 over should mic at 4.08" Those "hash marks" aren't what's making it leak. These marks are supposed to be there to pull excess oil away from the seal. You've just got a worn out seal.

 

i have replace the rear main seal 2 times. and looking at the other block i just got and there are no hash marks in the rear main seal area, on the crank

 

There should be. Looking from the back of the crank which way do the mark slant, right or left? The opposite rotation marine engines are different.

 

Are you sure that it is coming from the rear main and not the rear of the intake? I also had a 390 that I had rebuilt and was getting oil from the back of the engine. After changing the intake gaskets and making sure that it was not coming from there< pulled the engine and replaced the rear rear main 2 times. When it still leaked, I pulled the engine out and turned the oil pump with a drill and fond one of teh plugs for the oil gallery was installed wrong and that was where it was coming from. That was a long weekend.

 

I had the same problem also. Pulled the motor replaced all the seals and motor still leaked. Broke down and brought it to an old timer that knew the FE's. He ended up replacing all the oil gally plugs with ones from a spare block he had out back. no more leak.

 

Some reverse rotation marine cranks have the oil helix (slash, hash marks) going the opposite direction. That said there is a recent thread on FE.com about marine cranks. Someone mentioned there was a marine crank version with no helix marks used after 66. I found that interesting. But I've never personally seen one. And have had the pleasure of tearing down my share of marine 427's. I've also seen guys smooth them out but that leaves the journal undersize and leaks like crazy!!! You need to grind, weld and machine smooth back to oem specs to do this properly. And then use a neoprene seal instead of rope. You can check the crank for a JE in the casting number which denotes a marine crank. Reverse rotation cranks used either a C5JE-B or C6JE-D casting number. Also as mentioned one of the plugs in the rear of the block could be weeping under pressure. Early blocks used press in cup plugs and are prone to leaking. Later plugs were threaded plugs which are the way to go. Being your not seeing the helix marks you might wanna measure the dia of that journal to see if it's undersize. If so that's probably the problem. The helix marks are sometimes hard to see if your doing this with the engine in the truck. But you can run your fingernail on the journal and feel for them. Also check FE.com for that thread. Might give you some further info and insight. Good luck. Some of those oil leaks are a bitch to find and correct. I've had some engines no matter what I did were just seepers and leakers. Others were fine. LOL.

G.

 

You need to verify the stroke or pull the the stamp number off the crank to determine your 360/390 issue.
--Mike

 

ok... i looked at my crank that is in my truck...the hash marks ive seen are on the last journal before the rear main seal.

im sorry my bad.