'68 390 autopsy...well sort of

[AlanCasida]

I pulled the 390 out of my '66 F100 to replace the rear main seal and all gaskets in general. It was running great when I pulled it with the exception of losing a lot of oil pressure when it warmed up. I think it came out of a '68 Fairlane/Torino according to the engine tag that was still attached to it and as near as I could tell has never been apart. I was curious as to what condition it would be in. It is fairly clean inside . All the nylon was gone off the timing gear and was in the pan. I am surprised it didn't jump timing but it might explain some of the idle inconsistencies it had. I confirmed it was leaking pretty badly out of the rear main seal, both the crank and the side seals. I pulled the main and rod caps and the crank journals looked really good although there was quite a bit of copper showing on the main bearings. I mic'ed the journals as best I could they all appear to be still standard. I put some plasti gauge on the thrust bearing and it didn't squeeze it enough to reach .003 so I am figuring around .005. That probably explains the loss of oil pressure when it warmed up. Since it ran so well before, all I am going to do is re bearing it and put on a new timing chain and gear and oil pump and put it back in the truck. I don't think I'll even pull the heads. Anyway, I thought you guys find it mildly interesting to see what an untouched 53 year old motor looked like.

[frnkeore]

Nice looking 50+ internals.

I had a pump drive shear, with that nylon crap (got into the pump, threw a gap in the screen).

Are you going to pull the cam and check it for wear?

My opinion only but, I think I would pull the heads and do a valve job, while it's out and if the cam shows wear, put in a small RV cam.

Nice VJ might pick up a few HP, too.

[The Real McCoy]

Looks like the rear main seal is a lip seal, when did Ford go away from the rope seal? I took a 100% original 352 apart recently out of a 65 F100 and that still had the rope seal.

Your engine looks incredibly clean for a 50 year old engine. Certainly doesn’t have the typical sludge deposits that I’m used to seeing on an old engine.

[AlanCasida]

Looks like the rear main seal is a lip seal, when did Ford go away from the rope seal? I took a 100% original 352 apart recently out of a 65 F100 and that still had the rope seal.

Your engine looks incredibly clean for a 50 year old engine. Certainly doesn’t have the typical sludge deposits that I’m used to seeing on an old engine.

That's what I was wondering too. I don't know when Ford went to the lip seal. I did see a Ford p/n on it but it could have been replaced at some point.

[AlanCasida]

Nice looking 50+ internals.

I had a pump drive shear, with that nylon crap (got into the pump, threw a gap in the screen).

Are you going to pull the cam and check it for wear?

My opinion only but, I think I would pull the heads and do a valve job, while it's out and if the cam shows wear, put in a small RV cam.

Nice VJ might pick up a few HP, too.

No I am not planning on pulling the cam. It probably could use a valve job. When I had the valve covers off I laid a straight edge across the valve stems and they were all over the place. So I know pulling the heads will just open up a can of worms. I just want something to run around in and I am not concerned about how much power it makes. It ran down the road good and the plugs are nice and clean so that's good enough.

[Rory428]

Even if the heads didn`t need valve work, I would replace the valve stem seals, as chances are, they are rock hard, and will crumble into pieces, and try to get into the oil pump.

[AlanCasida]

Even if the heads didn`t need valve work, I would replace the valve stem seals, as chances are, they are rock hard, and will crumble into pieces, and try to get into the oil pump.

Yeah, that's true. I may pull the heads yet. Right now I am undecided whether to keep the truck or sell it so I don't want to put a bunch of money into it that I won't get back.

[BruceS]

Alan, when you say it lost a lot of oil pressure when it warmed up how low did it get?  Was it at idle or all through the RPM range?  No doubt the bearings need replacing and the engine has given good service.   

[AlanCasida]

Alan, when you say it lost a lot of oil pressure when it warmed up how low did it get?  Was it at idle or all through the RPM range?  No doubt the bearings need replacing and the engine has given good service.   

It lost oil pressure at idle when warmed up. Running down road it had around 30psi with 10w40. at idle in gear it was around 5psi, low enough for the oil light to flicker. Idling in park it was maybe 10 since the engine was running a little faster. Since I wasn't going to use the truck for anything but to run around in I wasn't real concerned although I did switch to 20w50 which brought it up to around 8psi at idle while in gear. But since I have it apart I thought I might as well slap some bearings in it to see if it helps.

[Rory428]

Over the years, I have had several old, tired FEs, that would occasionally flicker the oil light at hot idle in gear, and with a mechanical oil pressure gauge, barely register. But they ran for years like that, and when taken apart, other than the expected bearing wear, nothing seemed to have really suffered from low oil pressure. Although I certainly wouldn`t try to add a bunch of added HP to such an engine, nor would I be happy with a fairly fresh engine being this way, but for an old , tired piece, the seem happy enough, and can run a long time like that.

[gt350hr]

   '67 for the lip seals. The one you have should have a C7AE part number on it. The 427 SOHC actually used an orange silicone lip seal in '65 and Ford serviced it in their complete engine gasket sets. I have owned several of the gasket sets.
   Randy

[HarleyJack17]

Just food for thought, the re-bearing will help with the oil pressure, but wear on the rockers bleeds a lot of pressure/oil off. While you have it down, I would recommend checking/repair anything out of spec and limiting some of the oil to the heads. Easy to do even if you don't pull the heads completely off. Just my .02. Very very clean motor.