smoke from the exhaust

[lcfman]

I have a small amount of smoke coming from the exhaust on a freshly built Chevrolet 348/409 engine. The engine was rebuilt .030 over with fresh rings,
valve seals and a custom aluminum sheet metal intake. I did not machine the block deck. I suspect that the intake is leaking and sucking oil from the lifter galley into the cylinders but I am not 100% sure. I need a test or inspection to determine were the leak is coming from. Any suggestions would be greatly appreciated. The sheet metal intake is two piece with a lifter valley plate and then an upper plenum on top of the lifter valley plate.
thanks

[ustahava67]

Smoke machine test?

[mag2555]

Smoke out from both banks of cylinders?
What type of rings?
Many folks make the mistake of running Moly plasma face rings that need to be seated on dry cylinder walls and then proceed to lube the walls during assembly.
Have you given the motor 3 or 4 full throttle blast to see if the issue improves?
Do the back side of the Intake valves look wet from oil?

[lcfman]

I also am considering a smoke test as I have access to a smoke machine. My concern is what to look for in the area's where the smoke comes out. Obviously if smoke comes out of the sides (manifold to valley plate) then there is a leak to atmosphere, but a leak from lifter valley to head is hidden.
Were would the smoke come out? The spark plug holes?

[Firedome8]

Some times a shot of carb cleaner into crank case wile ideling will reviel a vacuum leak at manifold to head interface,,,inspection lite to look at ports,,,oil on plug ?

[ustahava67]

I also am considering a smoke test as I have access to a smoke machine. My concern is what to look for in the area's where the smoke comes out. Obviously if smoke comes out of the sides (manifold to valley plate) then there is a leak to atmosphere, but a leak from lifter valley to head is hidden.
Were would the smoke come out? The spark plug holes?

Smoke would be coming out the Carb throttle body if you pressurize the crankcase. I would get one of the cheap bore cameras also and have a look down the ports. I found a Chinese camera for 12$ that works with phone or laptop. 7mm diameter on a 3 meter cable. Really hard to beat.

[DaveMcLain]

How much have you run the engine? Just last week I was doing some dyno testing of some mufflers and one of the sets I tested had been on a car that had run with a cracked cylinder which must have filled the exhaust system with anti freeze. That muffler was not wet or anything but once it got warmed up it smoked like crazy for probably 30 minutes or so before it finally quit. You don't have a bunch of new exhaust system stuff that hasn't burned clean yet do you?

[lefty o]

what color smoke? no point jumping to conclusions without knowing if its fuel,oil, or water.

[Belgian1979]

I also am considering a smoke test as I have access to a smoke machine. My concern is what to look for in the area's where the smoke comes out. Obviously if smoke comes out of the sides (manifold to valley plate) then there is a leak to atmosphere, but a leak from lifter valley to head is hidden.
Were would the smoke come out? The spark plug holes?

Smoke would be coming out the Carb throttle body if you pressurize the crankcase. I would get one of the cheap bore cameras also and have a look down the ports. I found a Chinese camera for 12$ that works with phone or laptop. 7mm diameter on a 3 meter cable. Really hard to beat.

Wouldn't it be necessary to have all valves closed ? I mean, the smoke will slowly migrate through the ring slots and up into the cylinder. If this happens, how do you know it's not coming from a manifold fitment issue ?

[ustahava67]

You could back off the valves. If you are looking with the scope/camera you should be able to see it coming from the manifold/head joint. even with the valves open 'Theoretically' there should not be much getting past the rings... backing off the valves would eliminate that possiblity

[geraldtson]

If your running pcv valve check hose at carb or intake end of hose for signs of oil to make sure its not sucking oil through system?

[modok]

You have assumed the smoke is from oil. Good chance it is, sure, but I'd be more certain if you also said it it eats a quart in X number of miles.
Is the oil level dropping? Too soon to tell?

[tenxal]

Why not take the carb off and run a bore scope down the intake port? With a sheet metal intake, it would be simple to do. If you're pulling oil from the valley, you'll know immediately.

[lcfman]

Thanks for the replies. I think I will start by running the engine a few minutes and bore scoping through the throttle body plate (induction is efi) and inspecting for oil and then go from there. My thinking is if there is oil in the plenum and runners its an intake leak.

[MadBill]

A quick check for crankcase leaks in general is to pressurize it through the dipstick tube with lung power. You can feel if it retains pressure, meaning no leaks anywhere, or leaks down. If you are a smoker or can press one into service, you should be able to pinpoint the latter's source by barring the engine over to successively close each intake valve, whereupon smoke should issue from that runner. For greater accuracy you can prop the throttle open. (or better yet remove the TB)