Oil Consumption/Oil in Manifold

[xix_vannin]

So I've been doing my research on this and I can't seem to find anyone who's found a solution to this problem just band-aids. Problem is I'm consuming about a quart of oil every 100ish miles. (yeah, it's alot) & 3 wet plugs.

stock 1988 HO5.0 motor (70k miles) w/1996 explorer intake, plugged egr hole in lower (Sectioned plenum 2" to fit application) , elbow and tb, rebuilt GT40 heads w/roller rockers (baffle cut for RR)

It only smokes if I rev the engine up in park or when I'm driving and let off the gas on high vacuum decel. I immediately do a leak down test that showed less than 10% leak down per cylinder. I checked my line from the tb to the vc and it is clean. I swabbed it with a que tip and it had some residue but nothing crazy.

On to the PCV. It has a new PCV so I checked the line from it to the intake and it seems to be pretty clean (swab came back with just some light residue.

I'm thinking well it HAS to be valve seals, even though the heads were just rebuilt, maybe something was over looked. I pull the intake and it shows quite a bit of oil has been in there, the gasket between the upper and lower intake was wet on the "back" side. I get to the valve seals and a lot of them were sliding up and down with the valve. I'm thinking BOOM there lies my problem.

I changed all the valve seals, start it up and do some quick revs after it warms up and seems to have cured my problem. I get on the FWY and let off the gas to exit while looking in my side mirror and sure enough, here comes the smoke... I drove it around for about 20 miles, came home and checked my dipstick and yes it's burning oil.

HOW am I burning oil? I'm stumped and lost at what more avenues to check? Any help is MUCH appreciated.

 

[General karthief]

Lower intake gasket slipped sucking oil from the lifter valley? Likely not, just thinking out loud, they usually have a vacuum leak too.

 

[xix_vannin]

Lower intake gasket slipped sucking oil from the lifter valley? Likely not, just thinking out loud, they usually have a vacuum leak too.

Thanks that may be the next thing I have to check because I'm lost on where oil is getting into my intake from. Thanks

 

[mikestang63]

when you did the leak down test did you hear any whistling in the throttle body, intake plenum, Oil Fill tube, dipstick tube or out the exhaust? That would tell you where the problem is.

 

[xix_vannin]

when you did the leak down test did you hear any whistling in the throttle body, intake plenum, Oil Fill tube, dipstick tube or out the exhaust? That would tell you where the problem is.

No, nothing, it's weird because I have 3 cylinders that the plugs are dark and one of those three the plug is literally wet with oil. compression on that cylinder was 150 and the leak down showed about 10%. I'm completely stumped. dry pcv, dry vc to tb tube. but the intake is a little wet on the inside. Could this be a lower intake problem of some kind?

 

[90sickfox]

It could be a lower intake issue... but that's a lot of oil...a quart every 100 miles.

When you changed the valve seals did you check the valve stems for side to side play ?

The lower intake could've slipped. That usually causes some idle issues though. Would make sense though since it happens at high vacuum.

 

[General karthief]

A quart every hunnert miles, thats serious! If it were a slipped intake gasket you'd have some issues just trying to drive it, it would smoke a fair amount too. I'd be pulling the valve covers off and checking those valves like mentioned above.

 

[Martman]

I have the same problem and have done everything except rebuild the bottom end. A friend of mine who is comfortable rebuilding engines said most of the time this is due to seized oil control rings from someone not changing the oil enough and/or the car being run too hot for too long but not enough to blow a head gasket.

It is visible on my number 6 cylinder and gets progressively worse on the 7 and 8. He said there is not much you can do except rebuild. He said soaking with seafoam sometimes works but most of the time it is a lost cause. I have a small catch can and don't get too much oil in there (definitely not the amount I burn).

I ran a scope and you can see on those cylinders where the edge of the pistons are clean and he said that is almost a certain sign of oil control rings.

You can see the difference in the 5 cylinder and number 8 in the images below.