I just got this real Lingenfelter 383 for cheap. It was removed from it's original home in front of an automatic trans under the hood of a 91 Corvette because it smoked upon decelleration. It did not smoke idling, or under a load, just under engine braking (the car was used for Autox and roadrace). The plugs are a bit dark but they look pretty good and are not oily. There arent many miles on this motor and it made 340hp and 540tq at the wheels. No that is not a typo, this car had a bit of a stall converter and a 3.55 gear, I have the actual dyno sheet from LPE and it shows the numbers and the torque curve and it goes to 540ft lbs, dont ask me how, maybe the automatic and converter are lying to the dyno. Either way the engine seems to be healthy. The owner said he always ran synthetic oil since he had it so I just assumed he never broke it in right and the rings never seated hence the smoke. See the attached pictures. There are black streaks in the intake ports of the heads. Each port has a streak in the same location on each intake port although some are larger than others. Upon examination of the intake manifold gaskets it seems that the intake may not have been sealed very well. From the black streaks in the ports it appears that the engine may have been sucking oil vapor from the valley. The EGR was disabled on this engine so the plenum, runners, and upper roof of the intake ports are perfectly clean. Anyone else seen these streaks before and if so what do they mean? For more pics go to my post on the TPI board

https://www.thirdgen.org/forums/tpi/...lacing-my.html

Needless to say I am glad I spent the long dollar on my trans swap and got the TKO600!

 

It looks like it was sucking oil past the intake gasket. Thay would explain the smoke on decel (high vacuum).

 

Being an original Lingenfelter engine I will assume the heads have been ported. Any chance that's an area of the intake port they epoxied up and then ground down during the porting process?

If you had oil getting sucked past the intake gaskets it would also be caked up like carbon on the backs of the intake valves, similar to having worn out valve guides/seals leaking oil.

If you're sure it's oil discoloration I'd also wonder about sucking oil in through the PCV system (I assume it's still got one of those).

If you had an intake gasket leak on all 8 it wouldn't idle worth a damn.

 

Well the heads have been heavily ported but I see no evidence of epoxy and the faces of the heads are not damaged at all. The valve stems are perfectly clean, there are just those streaks in the ports which puzzles me. The reason I have suspected bad intake gaskets is because all of the streaks are at the bottom and one side of the ports. When I removed the gaskets they were shiny and a bit wet on the bottom where I suspect the leaks. It is strange that all the intake ports look similar to this. The engine had a PCV system but I do not know if it was adequate or if it even functioned. The previous owner says it would occasionally blow out the dipstick tube as well. With the kind of power this engine made before it was pulled I have to suspect a PCV system error or an intake leak in the valley but who knows. I'll be pulling the heads Thursday night, I guess we'll see what the cylinder walls look like then. Thanks for the opinions guys. Anyone else got any opinions pipe up!

 

its very possible thats what the problem is.
i had a motor that would dump smoke out the exhaust only during a turn, the faster i took the turn, the more smoke. in a left turn it dumped out the right pipe, on a right turn it dumped out the left pipe, it was caused by the intake not sealing across the bottom of the ports on every cylinder. other then the smoke & a large use of oil, it ran great. the problem was caused by the shop that did the heads for me, they took too much off the top side of them.

 

Look at that picture. I don't think thats epoxy. If the engine is low mileage, I could see the valves not having build up yet being that the back of the valve is so smooth. I would think the oil, if thats what it is, would stay along the floor of the port since it is more dense than the air flowing through it. That being said, while the engine is out, it can't hurt to replace the rings and bearings. Just be sure to carefully seal the intake up.

 

Well, if it was blowing the dipstick tube out I'd say your first guess (rings) was a good one.

Possibly it was only eating some oil under heavy throttle. Maybe pushing it past the PCV or maybe an intake gasket leak (possibly too small an intake gasket that was only BARELY sealing the enlarged intake ports up?). Still, check out the PCV system and make sure it's working right. If it is you won't push the dipstick tube out uless you're getting quite a bit of blow-by or somebody was running with the oil level too high.

Somewhere in all that is probably the truth. The epoxy thing was a long-shot but it's tough to tell from the photos.

 

Agreed. It looked too powdery to me to be epoxy. It doesn't make much since not to do rings and bearings if your pulling the heads off anyway. It could save you a big headache and more expense later.

 

A guess: a deposit of EGR soot in an area of low port velocity (short side radius, port floor).

 

Mean,

If the engine is out of the vehicle, you have a great excuse to freshen up the bottom end and rotating assembly. If you want to wear those rings in, just run some Pennzoil for a while. It doesn't lubricate cylinder walls for squat (no film strength), so they should seat nicely.

I'd take a close look at what remains of the lower intake flange/margin once the intake is removed - Your photo has too much glare to show the detail of that on the flange.

 

That was a good trade. In the old LPE catalogs that complete motor listed for $8995 I think. They used good hard parts also. The superram is a hard intake to seal, so take your time with reassembly, I wouldn't doubt that it was leaking.

 

EGR was disabled according to the first post.

It might just be an intake leak to the lifter valley. Might want to check the fit of the intake base to the heads, maybe the heads were angle milled or who knows what. Any evidence in the intake to match the heads?

 

Yes I saw that... but it doesn't mean the EGR was always disabled. And if I read it right, the comment referred to each intake port in both heads.

As I said -- it was a guess.

 

Thanks for all the replies guys, it helps me to know that I am on a similar wavelength to people that know what is going on. To reply to some of the comments above..

I still plan on re-ringing and installing all new rod and main bearings. Like you guys said now is the time so it is silly not to. This is a serious motor, i'm going to refrain from being a jackass and try to do it right.

I will take the camera home and get better pics Thursday night and then post them up for you guys. I am pulling the heads so I'll try to get some pics of the porting too. I'll get pics of the cylinder head surface, intake base surface, and pictures of the intake gaskets if I can focus on them. The intake gaskets were the crappy black "screen and cardboard" intake gaskets that i have seen stock on TBI motors. I recently replaced intake gaskets on a 50,000 original mile TBI pickup that was leaking coolant so bad it was running down the back of the block. The gaskets were just completely gone. That being said I have little faith in the intake gaskets that were used on this engine. I usually use the blue Fel-pro ones.

When I removed the gaskets from the heads they were wet on the bottom and dry on the top which also led me to believe they were leaking. I'll clean the silicone off the ends of the block and set the intake base down and look for a parallel gap between the intake and the heads.

I'll be pulling the heads Thursday night and I'll get more pics for you guys to see. Thanks for all the help. Stay tuned till thursday night

 

Wet with what? If the rings are shot and the intake gaskets are wet, maybe it was drowning in fuel at some point. What do the gaskets smell like? Oil and gas are distinctly different. Often hard to tell by just looking.

 

Well I did not actually touch the wet areas. I was disassembling this engine very slowly and examining everything as I went. I gently pulled the intake gaskets without breaking them. I was actually able to just pull them off the heads and intake without tearing them if that tells you anything. The only place they tore was near the water jackets at the ends of the block. This engine has sat for almost 2 years before I got ahold of it and I did not smell fuel while disassembling it. I would have thought fuel would evaporate out in that amount of time anyway. I'll look at the gaskets again closely and see what I can find on them.

 

I pulled the cylinder heads last week and the combustion chambers and the tops of the pistons werent even completely covered in carbon. The cylinder walls look perfect with crosshatch and all. I had planned on rebuilding the engine but with the seemingly obvious intake leaks, and with the rest of the engine being so pristine, I am going to just clean the heads, and reassemble everything with new gaskets and run it. It just seems foolish at this point to disassemble an engine that is in perfect condition, besides I can use the extra money for a new flywheel, and on tuning. I'm also going to need some rubber to hook this thing up. Anyway, thats the update guys.

 

before you bolt the intake back on, make sure it sits down on the heads right.
also check the ends of the intake where it matches up to the valley on the block.

 

Well I cleaned the heads and intake and set the intake back down on the block and heads. When the intake is perfectly centered there is about .045" between the intake and heads, I checked with feeler gages. This seemed a bit much to me but I dont konw what the gap is supposed to be in the first place. You can buy different thickness intake gaskets so I may go that route. After I pulled the heads it appears they were decked but I obviously don't know how much becaue they aren't stamped or marked. I am going to use thicker gaskets and just a smear of RTV to seal them up this time so this doesnt happen again. Then once the engine is in and running well I'll go out and break my rear end...

 

i don't know what it should be, but .045 does sound like a bit much for stock gaskets, maybe someone who knows can answer.
check thickness of the gaskets before you put them on.
was the intake sitting down on the valleys when you checked it?
don't use the rubber or cork valley gaskets, just a nice bead of a good quality silicone.