LOTS of smoke!

[JEFF]

Here is the scoop - Fresh hone and rings in .030 over flat top pistons in the L24. laped the valves on the N47 and assembeled with new gaskets.(cylinder compression is at 180 psi across all 6 cylinders) I have the fuel injection for the '78 head all figured out. Last night i started it up. Started up on the first piston to the top- i was excited!!! After timing it - i let it run about 8-10 min. to clear the cylinders of the assembly oil and seat the rings alittle. I shut it off to have a celibration ciggerette. I have oil dripping out of the header - I ran it some more - Dripped alot more - ran it some more - dripped more - after about 1 hour of the smokie shop i decided something is not right - Go to the site and ask -- ANY SUGGESTIONS GUYS ???

- Jeff

[beandip]

check the compression . did you check it after running and warmed up ?what did the pluggs look like. Are you sure it is oil and not water with soot driping from the tail pipe ?? with the winter cold and dampness it could vary well be moisture that has collected in the exhaust

[Ed]

Jeff you said you had oil dripping out of the header. I assume that there is no exhaust on it. Just a header? And does is smoke pretty bad when you first start it up? Or does it smoke the whole time?

[Royce]

First check the spark plugs to determine which cylinder it is. This may also give you a clue as to what fluid it is.

What color is the smoke???

If you are indeed leaking something into the combustion chamber than it sounds like a compression check and leak down test may be in your near future. Again, a visual on the plugs will get you on the right direction. Let us know what you find.

[JEFF]

The compression was 163 - 167 psi before the first start up.

1/2 hour later it was 180 psi across the board. cylinder leak down test showed about 8% leak down - I was told that was really good. The valve seals were not replaced during the head swap - new ones are on order as i type. the smoke is from oil getting into the comb. cham. The header is wide open without the 'y' pipe on it - the oil drips from the pipe coming from the front 3 cylinders , so i pulled the plugs out - #3 is very oil fouled - #1 & #2 are alittle oil fouled -- #'s 4 - 6 look good. I am thinking the valve seals are the problem - what do you think?

Thanks

- Jeff

[Royce]

But have you done the leak down test and compression tests since the leak???

I can understand that some of the plugs might look worse than others, could depend of valve position at the time you pulled out the plugs. But the fact that it is all the front cylinders is interesting. Is there any way that your front carb is pulling in oil somehow. Maybe if you are using a aftermarket/custom air cleaner setup with only one carbs connected to the PCV or vavle cover breather or something like that?

It could be the valve stem seals, but this would have to mean that the vavle guides are really trashed too! Back in the old days OHC engines didn't use vavle stem seals, this is both before my time and before the Z's time. Over time the valve guides would wear and when the engine sat it oil would collect on the back of closed vavles or in the combustion chamber. When the engine was started it would blow blue smoke, oil, out the tail pipe. Once the engine warms up and the metals expanded the oil leak would be sealed off and the smoke would stop. Then next time the car sat for a bit it would happen again.

Now this is before the use of valve stem seals and also before the use of hardened vavle seats and more importantly hardened valve guides. The N47 head has hardened valve seats and guides so I am surprised that you would have that much leak. And I would also be surprised that it won't go away after warming up the engine throughly. Are you letting the engine warm up and run it after it has reached opperating temperature (180 - 190 degrees F)?

If compression and leak down tests with the engine warmed up are still good then putting on new valve stem seals may very well solve the problem. You may have some wear in your valve guides as well, but I don't know if that is necessarily a big problem on a L6.

Maybe someone else can shed some light on the issue of when a worn valve guide is a problem!?

Hope it helps!

[dozer171]

my N47 head had 130K miles on her when i rebuilt it, and that only included dismantling, cleaning, and lapping the valves. i put it together with new seals (left the seats and guides in place, they all looked good), and i consumed a very small amount of oil over the first 500 miles. i talked to my dad about it, he said to write it off as the rings seating after the honing job we did. she hasn't consumed a drop since (about 5K miles).

his 87 pontiac fiero GT on the other hand.. oil monster! has about 140K miles of being driven HARD every day. she goes through about a quart a week depending on the amount of driving and the style. she needs new valve seals REAL bad. it's gunna happen the next weekend i'm home from school and it's nice out (which is starting to happen here in my area of new york! sweet!!!! )

if you didn't replace your valve seals, i would reccomend doing them. if it consumes a VERY small amount of oil, wait until the rings are broken in (beyond seated, about 200-500 miles of gentle driving).

are you sure your carbs aren't overfilled with oil and they're just leaking down until the level gets to it's correct point?

[JEFF]

dozer171 - When i put the '78 N47 head on my L24 block I also put on the '78 fuel injection and electronic ignition. Yeah Oil carbs no more!

Would you think that the valve seals COULD leak enough on an intake stroke to let in a nonburnable amount (lots) of oil so that it drips out of the open header ?

When it runs at idle it is splattering alittle bit of oil on the floor - if i bring the rpm up to 1500 or so for 1 - 1 1/2 min. then it spits alot more than at idle, then shut it off and a puddle about the size of a softball will form in a few minutes. Valve seals are being installed tomarrow. Do you think this is the problem??

Thanks for responding to my post

- Jeff

[dozer171]

if your seals are as shot as the ones in my dad's fiero, yup! ! man, he gets a nice healthy puff of blue smoke every time the motor starts and a james bond style smoke screen every time he romps on it... i spotted him about 50 yards up the road, so i downshift and took off after him, well, he did the same and gave me the pleasure of expiriencing first hand how much oil his car can burn! my poor Z stunk all afternoon! i would replace the seals and see what happens. also, while you are at it, replace the PCV valve, because if this is metering excess blowby into the intake, it very easily could be allowing oil to see up. did you put the baffle back in when you built your motor? there should have been a metal plate on the side of the casting inside right under the outlet. that holds in a folded up wire mesh with the purpose of blocking oil and other contaminates from making their way into the intake...

[JEFF]

Yes i put the baffle back in correctly after cleaning it. The PCV is brand new. the valve seals are in at the store .. they go in the car tomarrow - i will post late tomarrow night what i find and what happened. Thanks for your support.

- Jeff

[dozer171]

hope it works out!!!!