Hi Folks! Am new to this forum, but I have learned a good deal by reading some of the threads re my concern. The knowledge level here is great, and this is a much easier site to navigate than some others. I have need for some experienced advice on a 390 in my 70 Ford XL convert. I know this is a truck site, but my XL does have a 1976 390 truck 4 barrel manifold (390's in big Ford cars in 1970 only had 2 barrels).

Purchased this excellent XL convertible 12/05, but noticed fairly heavy blue smoke recently, most noticeably on the left bank. Following new 650 Demon carb installation, engine now starts and runs great! Valve train exceptionally clean, compression check (done correctly) on all cylinders registered between 140 & 150, and engine seems in exceptionally good condition. Following forum suggestions, have installed Holley .070 jets to restrict oil. Replaced both rocker shafts (one was found cracked/broken during disassembly). Rocker arms in very good shape, arm-to-shaft clearances seem excellent, rocker oil baffles in place. Both shafts installed with holes down and notches pointing correctly. Valve stem seals (umbrella type) are soft and pliable. Have run with valve covers off, oil flow good with no pooling evident. Smoke not present on start-up, but develops after vehicle warms to operating temp. Smoke amount now significantly lighter, but still present after warm up.... on left bank only. Intake manifold leaks externally at both rear corners (kinda bad) and at left front corner.

I suspect an internal intake manifold leak. What do you think?? While I'm at it, do you think I should replace the valve stem seals (I would use the rope "technique")? I believe I read here somewhere that there is a Buick seal from the 80's (avail at NAPA) that will attach to the FE head using a small spring in place of the FE umbrella seal and works well.....true?? Also, any suggestions on manifold gasket brands, i.e., FelPro, Mr. Gasket, etc., and installation tips would be greatly appreciated. I do have a cherry picker to use to lift off and replace the intake beast....that'll be a BIG help.

THANKS to any that reply, and I will repay the favor by watching this forum and contributing where I can.

 

it sounds like the intake gasket leaking. I had the same problem and replaced the intake gasket...still smoked. I pulled the intake off and it was wet with oil around the # 2 cylinder port, the exact cylinder that was smoking (fouling plugs horribly). So now I try again. This time I think I may put a tiny bit of silicone around every port in the head. Just as long as I keep the silicone far enough awa from the port to reduce the chance of it getting in there. unfortunatly i think this practice is frowned upon. I am just having a heck of a time getting it to seal.

 

If you are sure it isn't pooling oil on top of the heads then I'd be checking the intake manifold as well. I've had both problems with my engine. It's easy to tell if the intake manifold is leaking when you take it off. The intake ports that are leaking will have signs of oil in the intake ports of the heads but the intake runners on the intake manifold will be dry.

fwiw, I used high temp silicone on every port on the head and intake manifold when I did my last intake manifold install and I had no leaks. This is not the recommended way but I had had enough of the problems and I did my own thing....LOL. I think that Mr. Gasket intake manifold gaskets are supposed to be the best but I had difficulty getting them and I ended up using a standard Fel-pro gasket.

Tracy

 

falconstng...did you use silicone on both sides of the gasket or just one? and sorry heapbigengine, i didn't mean to hijack your thread...............

 

I put a narrow bead of silicone on both sides of the gasket....I did the side towards the heads, put the gaskets in place, did the side that faces the intake, put a heavy bead on the ends of the block, and then carefully placed the intake in position. I put in all bolts and snugged them up....just barely tight. I let it sit overnight and then torqued to spec. Keep in mind this is unorthodox....This is the first time I used silicone on intake gaskets but I had enough problems that I decided to try it.

Tracy

 

I see, good idea.. I am very confused though, because I had traces of oil around the intake port (under the gasket), and the plug is actually wet with oil, but there seems to be no oil inside the intake port of the head...? is this possible? could the head be cracked or something. And this leak is bad....at idle it will drip oil out of the exhaust manifold! i am at a loss. the engine is in a stand and i have a different set of heads for it, i just have to drive 4 hours round trip to get a valve job at the nearest town..any help on this matter would be great......Brad

 

Oil under the gasket is a sure sign the gasket was leaking. I had this problem as well as pooling in the heads after I rebuilt my engine. I had installed new adjustable rocker assemblies from DSC and I had installed a new performer RPM intake manifold. The rockers and possibly a HV oil pump together caused pooling and I had trouble with the intake sealing. Both of these problems cause smoking and HUGE oil consumption. I've restricted my heads but the pooling is still a bit of a problem....not nearly as bad as it was but I need to get to the bottom of what's going on there. I solved the intake problem with the RTV sealant. I actually had it solved using permatex aviation sealer but I pulled it back apart because I had the pooling problem and I thought it was still the intake. As for the pooling, you have to see the top of the heads when you're running the engine at normal cruise rpm. Mine is ok at idle but when I run it up higher it will build oil....not so much to be above the valve guides sitting there but when I accelerate hard the oil pools at the back of the head and I get smoke then. At any rate, sounds like you have the intake problem. Make sure that the intake isn't warped and then replace the gasket using some form of sealer. Be sure to install it properly...correct length bolts, proper torque and tightening sequence. You should be fine.

Good Luck!

Tracy

 

Next time you suspect an intake gasket leak, try this:

1) Lock tranny in 1st
2) Rev it out to 4000RPM or so.
3) Let off the gas QUICKLy
4) Let it rev down to 1500RPM
5) Hit the gas

If you get a big blue PUFF and then it clears up a lot, that's almost 99% sure that it's the intake gasket. The intake ports in the heads were clear, I think it was the gas washing away the oil.

(don't ask how I know )

art k.

 

awesome, thanks alot..do you think i should avoid putting on the new melling hv oil pump? The oil pressure was low before, so i figured i would replace it while the engine was out. I also bought .087 holley jets to restrict oil flow. They just drop into the oil gallery under the rocker stand right? i really appreciate all the help.....brad

 

For a new rebuild my opinion is an HV oil pump is not necessary and could actually cause problems. For an older engine with low oil pressure then I might consider an HV oil pump. I'm sure you can get different opinions on this...I did install one but I'd take it back out just as quick if it wasn't so hard to do (I have a windage tray and FT oil pan so I'd have to pull the engine to change it).

Tracy

 

Thanks to you folks that replied to my thread....I do appreciate it!

After having read more on the whole smoking FE subject, I think I do have a leaking intake. I also know after close inspection yesterday that the intake is leaking quite badly externally at the rear on the left side....the same bank that is still smoking. It is probably a sign that the intake is leaking internally as well. Since the valve stem seals are nice and pliable, I will go after them if my intake repair does not resolve the problem. I will update this thread in the near future. Thanks again!