smokin' NSX (after rebuild)

[nsxtas]

hi, i have just rebuild ny nsx after some trial and error with a SC.
rebored and all new pistons and rings and so on, it runs great in traffic and on the freeway, but when on ideling is starts to do some severe smoking from the front bank (throu the exhaust, just on ideling) if you rev it up, it stops, and when the engine its cold, no smoke at all....
from what i can tell the oil and water consumption is not severe, but I guess the smoke is from one those sources.
i just cant figure this out, so i try a post here before i take the head of for inspection...
have anyone had anything like this? no one over here have heard about anything like it
brg
Martin

 

[ScienceofSpeed]

You should probably list some vital info such as:

1. how much was the block overbored?
2. stock pistons/rings?
3. if stock pistons, is the overbore within factory spec or, were overbore pistons used?

A break in period is required for new rings to seal properly. If possible, break the engine in before the supercharger is installed. If it does not go away after about 200 miles, you may want to do a leak down to check where your leak is. At that point, you can see if you have a guide seal problem, or if the problem is in the bottom end due to improper piston-cylinder wall clearance or improper ring end gap.

Your engine shop should be able to answer these questions for you.

Hope all is well & good luck,
-- Chris

 

[nsxtas]

thanks for your help Chris,
I have now removed the intake, and found visible traces of oil on the intake valves (both of them) and there was oil on the spark plug on that cylinder.
there is traces of oil all´the way up to the intake gasket, do you think it can have swirled up there?
i gonna take the intake apart tonight and se if there is any oil inside, and if so, check out how it got in there...

the compression test shows no traces of lower compression on that cylinder, its slightly a bit higher than the rest, I guess because the oil in it.

 

[ScienceofSpeed]

Compression findings sound right - oil increases the ring's ability to seal, especially during a compression test when the cylinder is not firing.

It would be a good idea to pull off the manifold, VVIS, and lower pan on the manifold to see if oil is pooled in there. It woul be unusual, but may be possible if the supercharger was pressurizing the crank case or valve cover area. Check for any other sources of leaks or oil being introduced into the intake manifold as well, perhaps from the valve cover breather tube.

good luck,
-- C

 

[nsxtas]

I struck oil!
in the pan under the vvis butterflies there was like 1/2 cup of oil, it seems like you said Chris, leftovers from the big bang.
(looks old and dirty)
will rebuild saturday, and hopfully no smoke after that, otherwise look into the hoses and se why it is filling up the intake with oil.
thanks a bunch, chris.
/Martin

 

[Larry Bastanza]

Hey Chris,

Nice catch.

Thank You,
LarryB

 

[nsxtas]

still smoking.....
after cleaning the intake, the smoke is still there.
so now i just removed the head to check whats up....
that bring me to a new question, what kind of cylinder-bore should one have to a set of 92,00mm pistons, if one have planned to do some moderate overboost (12psi)
thanks in advance
/Martin