[extech]

i think the viton positive seals require machining of the guides

 

[m in sc]

that may be true, but i don't think so on the one si listed (some do for sure though). worst case, just buy a quality engine gasket set or visit your local machine shop that builds heads, they can get them for sure. .02

 

[chris530]

Pull the vacuum hose off the transmission modulator. As previously mentioned the transmission fluid can be sucked into the manifold. The modulator is easy to change and not expensive.

 

[chris530]

When I had valve seals go bad it would only smoke at startup and then stop. It would do it every morning til I replaced them. That said I don’t see the seals being so bad that it sucks oil nonstop. Maybe I’m wrong hope you fix your issue with them.

 

[vespaholic]

Before you go crazy, pull the valve covers on that 390. The oil return holes in the head can get clogged. Check that first and clean them out if they are clogged. Worth a shot. Common 390 problem.

 

[m in sc]

When I had valve seals go bad it would only smoke at startup and then stop. It would do it every morning til I replaced them. That said I don’t see the seals being so bad that it sucks oil nonstop. Maybe I’m wrong hope you fix your issue with them.

mine started like that, for quite awhile (mos), but eventually would get worse as time went on it was like a freight train at hot idle before i changed them, and it happened quick once it started.

 

[Touring919]

I’m asking for myself and the OP. Can viton seals be installed on a stock head? I thought viton seals required machining. The as cast surface and shape is no good for press on seals. Am I correct?

 

[808Mark]

I’m asking for myself and the OP. Can viton seals be installed on a stock head? I thought viton seals required machining. The as cast surface and shape is no good for press on seals. Am I correct?

From my understanding, the standard sized viton positive seals won't require machining as they slide over and seal around the guide. I've seen others that have a metal band around the bottom that do require machining. I was trying to install 3/8 x .562 valve stem seals this morning and found out the valve stem guide is closer to .625.

 

[808Mark]

Before you go crazy, pull the valve covers on that 390. The oil return holes in the head can get clogged. Check that first and clean them out if they are clogged. Worth a shot. Common 390 problem.

Do you remember where they are? I'm having a hell of a time finding them. I can see how the tin directs the oil to the lifter valley of the intake, but besides that I can't see any type of small hole in there. I did notice the two large holes at the ends of the head right under the head bolts.

 

[m in sc]

thats them.

 

[808Mark]

thats them.

Got it. Okay well I think I'm good. The holes are fairly large, maybe 7/16 diameter, and there's not any sludge in there.

 

[extech]

looks like your guides are already machined for pos. seals

 

[Spyder]

check the valve seals

I agree with that really if it is a FE they have a taste for valve seals

 

[808Mark]

looks like your guides are already machined for pos. seals

I really wanted to put the positive type valve stem seal but the guides were about .654. I couldn't find a seal to fit them :/ I ended up using the umbrella style seals.

 

[ShotRod64]

I had a different make van that the longer it idled the more it smoked! Great mosquito killer rig! I sold it before ever doing anything to it. Worst vehicle I ever owned and wouldn't own another even if it had 30 miles on it was $500 unless it was to flip it!