Well I finally tore into this smoking engine of mine. It seems that it is the intake manifold. The ports were dry in the manifold except right at the gasket and the gasket and the intake ports are all wet with oil. The gaskets were oil soaked only at the very bottom of the port. The Intake manifold gasket surfaces seem to match the heads but I do see that the Intake manifold doesn't seat down quite as far as I'd like....The bolts all start but they are basically at the bottom of the intake bolt holes....I think the root cause of that is using the steel shim head gaskets which put the heads about .020 lower than a stock gasket. I'm not sure what to do at this point. My local tech help said to use Mr. Gasket intake manifold gaskets as they were better but someone on here said they didn't like them. I used standard Felpro before. I was also wondering if I should use a gasket sealer. I usually spray these gaskets with copper spray-a-gasket. I didn't use anything this last time because of discussion on here some time back and it seemed the prevailing thought is that today's gaskets perform better without added sealers. Everyone feel free to jump in with advice. This is the 2nd rebuild of this motor and the 3rd time now I've pulled the intake manifold. This probably was the root cause of the smoking problem the first time around and I missed it. At any rate, this is likely to be the last time I do this...regardless of whether I get it right or not....Working on this 390 has been a lesson in humility for me. I used to be considered a halfway decent mechanic....after seeing this truck smoke so much after my rebuilds It's become apparent to all who know me that I'm just a bumbling idiot...LOL. Help!!!!

Tracy

 

Someone mentioned using shorter bolts to install the manifold.. this way they wont bottom out. Never had a FE open to this point myself, timing chain and the like has been it..I cant see any gasket not getting a sealant but ??? letting the sealant set before starting the motor is something to suggest (if not the case before) 2hrs or more...Also several have suggested getting help with the intake placement to avoid shifting the gaskets..BOL wish I had the majic answer..

 

The problem has to do with heads being shave and the manifold being shaved to match. You need to make a bunch of measurements of the engine between the heads and port heights etc and the same with the manifold and find out what needs to be cut where, to fit, if it is possible.

 

This was a common FE problem and not unique to your engine. The intake gaskets were always sucking in on the inside bottom. The lost vacume running problem was usually worse than the smoking problem. We worked on a ton of these in the 70's when U-Haul trucks were all F600's. They all had 331, 361 and 359 engines. I think the only fix availible to us then was a good couple coats of High Tack on a new gasket. Definitly check out what Bear said above. The Permatex Aviation Sealer is a little sturdier than High Tack.

Ken

 

This is your problem. Your bolts are bottoming out. It was not the head gasket. Look at the geometry of it. The head gasket wouldn't make the intake bolts go any deeper than they otherwise would have.

This is a known problem with stock intake bolts and aftermarket aluminum intake manifolds. The solution is to chop about 1/8" to 1/4" off the end of the four offending bolts, or go to the hardware store and get the appropriate size bolts, or use washers to raise the bolt head so it doesn't bottom out.

 

I guess I didn't say it correctly. I mean that when the bolts start in the head that they are not centered in the bolt holes in the intake manifold. They are riding against the bottom of the intake manifold holes. I'd like the intake manifold to sit down just a bit further to line the holes up better. I think that raising the heads would also accomplish the same thing which is why I mentioned the head gaskets. I did cut off all my intake bolts and am sure they are not bottoming out in the head. Today I've placed the intake on there without a gasket and inspected. I don't see any obvious problem. The mating surfaces look parallel to each other. I wonder if I didn't start this because I didn't torque but to 20 ft lbs at first. I did come back and go to 30 but that was after it was already smoking. I can't locate any Mr. gasket intake gaskets so I'm going back with Felpro but this time I am going to use Permatex aviation gasket sealer on all surfaces. I'm also going to make the head oil flow modification and we'll see what happens.

Tracy

 

I don't know if this applies in your situation. I am certainly no FE expert. But as a general practice, clean up all the mating surfaces and insert carbon paper between them, ink side up, and press the manifold down in place. (old fashion carbon paper available from an office supply.) Use a soft hammer and tap the manifold in place applying pressure on the mating surfaces. The ink from the carbon paper will transfer onto the surface and show you if they are mating correctly. Use a sanding block to knock down high spots, (as indicated by darker ink,) on the manifold. Repeat as necessary until the ink transfer is evenly distributed. This will also reveal if the angle machined on the manifold is correct.

It does sound like the manifold surfaces need to be machined down to bring the bolt holes into alignment. Also you will see if your ports match up or not.