HELP I had my 1991 NSX with comptech supercharger and tuned exhaust rebuilt with new pistons. Original piston and one cylinder cracked after 9 yrs with super charger no damage to block so I replaced with new carrillo pistons. Well its been almost 10 months no one knows what is wrong I AM LOST. i just took it to NABIL in Orlando and still trying to figure it out. It still uses the oil after 10 months. It does not leak oil or no signs of drip or leak ever no smoke out pipes. It runs so good so much power no leaks no smoke just a little bit of black carbon on tips pipes no obvious oil leak anywhere just disappearing oil?? PLEASE HELP IF YOU KNOW ANYTHING. THANKS IN ADVANCE
Engine rebuild using 1 quart of oil every 300 miles
- Thread starter Bob
- Start date
What kind of oil? Some synthetics burn.
How do your spark plugs look? Are they oily?
What does your oil pressure read?
Have you run a compression check to rule out your compression rings? If so it could be your oil control rings.
You mentioned you replaced your pistons. I assume you changed the rings as well and that the ring gaps were rotated so they don't stack on top of each other.
I would recommend performing a borescope inspection of your cylinders. Look for scratching up and down the sides of the cylinder walls. This could indicate a broken ring.
You could have a cracked cylinder head near the exhaust port and/or spark plug hole.
Finally you mentioned "Original piston and one cylinder cracked after 9 yrs with super charger no damage to block so I replaced with new carrillo pistons". My question is how could you have a cracked cylinder and no damage to the block? Doesn't make sense to me.
What does your oil pressure read?
Have you run a compression check to rule out your compression rings? If so it could be your oil control rings.
You mentioned you replaced your pistons. I assume you changed the rings as well and that the ring gaps were rotated so they don't stack on top of each other.
I would recommend performing a borescope inspection of your cylinders. Look for scratching up and down the sides of the cylinder walls. This could indicate a broken ring.
You could have a cracked cylinder head near the exhaust port and/or spark plug hole.
Finally you mentioned "Original piston and one cylinder cracked after 9 yrs with super charger no damage to block so I replaced with new carrillo pistons". My question is how could you have a cracked cylinder and no damage to the block? Doesn't make sense to me.
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I just had my engine rebuilt and Shad recommends a thicker weight of oil on the new engine. He recommends a 10W40. This could be completely irrelevant to your issue. But there must be reason for him to tell me to use it. It could be lots of things. I would try a different brand or weight of oil first just to know for sure before doing all kinds of other tests. But that’s just me.
My 1991 Chevy K1500 used to use a quart of oil every tank of fuel. Changed the valve seals, now it can go four or five tanks before needing oil. The remaining oil is coming out the front main seal, so that's a big project I'm not ready to tackle until I have a back up car. FWIW, the engine has 330,000 plus miles on it. 
The spark plugs (as mwagner10702 mentioned) are a good way to check for bad valve seals (at least on the pent-roof Vortec engine it was).
The spark plugs (as mwagner10702 mentioned) are a good way to check for bad valve seals (at least on the pent-roof Vortec engine it was).
You’re losing oil from blow by would be my guess. Did they properly cross hatch the cylinder walls?
If your static compression is good then just keep adding oil, eventually you’ll have a mated ring and wall.
Don’t use synthetic until you see a decrease in oil consumption.
If your static compression is good then just keep adding oil, eventually you’ll have a mated ring and wall.
Don’t use synthetic until you see a decrease in oil consumption.
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