Thread: 390 Rear Main Leak..help!

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I have a 67 390 that we have redone and put into my dads 73 F350 camper special. The engine came out of an old bird I used to own and when we tore it down we found it was not just the run of the mill 390. It looked to be similar to the old PI 390. Anyway, after 30 over, crank turned, flattops, a cam and carb, we have an oil leak that will not go away. The rear main is leaking after trying a lip seal type seal and a rope style seal. A friend of my brothers told him the block is worn out at the rear main. My father was a master mechanic at a ford dealer for 30 years and he just is not buying that the block is worn out. I am having somewhat of a hard time with that idea as well. I do know that the engine has not been hurt, and was not leaking a drop when it was in the bird. Anyone have an idea about this? I need a new perspective on what might be wrong here. Thanks everyone!
Randy
Hartland, Mi

Ahhh....my bad...

Are these the seals you use the nails to drive through?

Did the machine shop turn the crank where the oil seal mates? You know the part of the crank at the flange end with the //////// hatch marks. If there was no leak before and there is now that the crank has been turned I'd look there. The hatch marks might have been machined off which will make the seal leak. Just a thought. G.

NASH>>>I DO NOT THINK YOU READ WHAT I WROTE ABOUT...THANKS THOUGH

FFR428>> The Hatch marks are all good and not worn. They did not turn that part of the crank. Thanks for the thought!

Originally posted by BIGINBIGOUT
NASH>>>I DO NOT THINK YOU READ WHAT I WROTE ABOUT...THANKS THOUGH

FFR428>> The Hatch marks are all good and not worn. They did not turn that part of the crank. Thanks for the thought!

I usta' work at a Ford engine remanufacturing plant. But.... that was 'bout 30 or so yrs. ago. If I remember right, doesn't the rear main on a 390 have seals on either side of the cap/to the block? Kind' of a triangle shaped stick of material that's suppose to expand when oil soaked to create a seal? If so.... did they get seated completely down in the slot? Just a thought?

Pro

You're 100 percent correct. Those get overlooked by a lot of fellows rebuilding a FE.

Yeah guys, that is exactly the type of seal it is. Dad has done many in his day and never had a problem like this with one sealing. I read an article about soaking them in oil and staggering the ends which I am not sure if it is something he has done in the past. I just spoke with my brother today and I am not sure that they know for sure if it is leaking at the rear main...They did replace all the plugs when they pulled it back out thinking it might have been the cam plug leaking. I know one thing, I will get the dye and find out for sure where it is leaking. Thanks Pro 70 and OldFordman!! c",)
Randy

Originally posted by BIGINBIGOUT
Yeah guys, that is exactly the type of seal it is. Dad has done many in his day and never had a problem like this with one sealing. I read an article about soaking them in oil and staggering the ends which I am not sure if it is something he has done in the past. I just spoke with my brother today and I am not sure that they know for sure if it is leaking at the rear main...They did replace all the plugs when they pulled it back out thinking it might have been the cam plug leaking. I know one thing, I will get the dye and find out for sure where it is leaking. Thanks Pro 70 and OldFordman!! c",)
Randy

Oh yea, I completely forgot about the oil plugs. Again my memory is a little foggy from 30 years of brain cells dien' off..... Aren't they a drive in plug like a mini freeze plug. Seems I got in trouble one time for not center punchin' the plug bore after installin' oil plugs. Or I didn't put sealant on the plug, or maybe both, I try to suppress bad experiences. He HE HE. Somehow it passed the engine check where they spun the engine to check compression and oil pressure. Plug popped out or leaked after the engine was installed in the vehicle. We had to pay for (The Company had to pay for) repairs. oooops.