bullitt4110

Pistons should be fairly clean after meth has been used for awhile and all else is good.

vegasredz062

And the 4000 miles are highway miles..

TurboLX

Sam,

The vertical scoring on the bores does not look "normal" to me at all. Are you sure the rings are clean, deburred, and properly installed? The scores provide a path for oil contamination you're seeing in the cylinders. I would suspect that you might have also been seeing some knock retard and/or your knock learn factor has drifted significantly from the high octane table toward the low octane table to compensate. This will destroy fuel economy due to the change in timing and reduce power.

Another possible area of concern might be if the methanol injection is bore-washing the cylinder, removing the oil which then leads to the scoring you're seeing. Reason #27 why I'm not a fan of meth injection...

knkali

interesting

PowerLabs

I can't coment on how the motor was put together other than to say that the shop that built it came highly recommended to me by several people.
As far as the fuel economy... The engine has a cranking compression of 145PSI, as opposed to 200 for a stock car. That's what is doing it. I saw zero knock ever on this motor, but even if there was, it would not explain why it gets 21mpg on the highway with cruise control on...

TurboLX

You may not be currently seeing knock, but if it saw enough before to increment the knock learn factor, the timing IS being retarded via the low octane table. Of course, if the high octane table just has lower values in it where the tuner may have worked around the knock, the timing is still retarded and the efficiency lowered.

Either way, that much oil in the cylinders tells me something's not right. Now it's just a matter of deciding whether you're looking at the chicken or the egg.

Pack Leader

Yeah, I don't see much of a crosshatch in those bores. And the vertical scoring normal? We have a saying here on the farm. Don't eat that Elmer, that's horse _ _it! Don't agree that the problem is the tune though.....

CONMAX

i agree with those that said the engine does not look normal. firstly, with meth, you should have almost no carbon build-up. i took my heads off my stock ls-2 with 11k boosted miles with meth and the piston tops looked like new pistons. oil must be getting by the rings and burning on the pistons tops. leakdown does't tell everything, you could have an oil ring problem and have 4% leakdown. you really have to take the pistons out and continue your analysis. sometimes the scoring is caused by the rings "end-butting" due to too small and end gap. the gaps need to be larger for a supercharged engine. another possibility is too little piston to bore clearance. due to greater expansion of a forged piston, the clearance needs to several thousands greater, dependent on bore size.

keep digging in, if you put it back together w/o finding the root cause, the engine will continue to deteriorate.

SinisterC6

wow I hope LME steps up and takes care of this, honestly its just embarrassing for their business to see a product look like this

i doubt your cam or tune is the problem, something is majorly wrong with the engine, i hope you make the power you paid for and wanted when this all gets straightened up

highpockets

Here is mine at about 4300 miles,when I swapped heads.twin nozzle meth and pistons did indeed look virtually new. Not trying to add fuel to fire,but I tend to agree,something is going on,either PCV issue or something.I really dont think the light verticle scratches are the issue,but I also do not see where all the carbon buildup is coming from.This will be interesting once you figure it out.

DREAMERAK

the oil will also lower octane causing knock-timing problems,and lower than expected power.

SGT

For what it’s worth by looking at your pistons your oil problem is not the rings. Possibly the valve guides or another source. With that much oil going by the rings the blow-by would run you out of the car. Also, when oil goes by the rings it leaves a clean edge around the piston. I know you changed the cam but were the heads also done? Could the lift of the ZR1 cam have killed the valve seals? Just my 2 cents worth……

Mr.Big

Just as a side note, the reason I run VP M3 is because of the additives that gaurd against bore washing... That's the main design behind this particular fuel...

PowerLabs

Quite the opposite: this running runs an extraordinary amount of ignition timing. 18 degrees at full throttle, 38+ at cruise.
Again, for all of those who think there is something with the tune: Doug from ECS tuned it, I looked at the tune, I datalogged the car. It is tuned well, it does not knock, it didn't knock on the dyno, it didn't knock on the drag strip, the pistons show no signs of knock, the spark plugs show no signs of knock.

It has worse fuel economy for the same reason it has a lot less power than it should: because it has a cranking compression of 145psi: it is a less efficient engine because it has a lower compression ratio. There could definitely be more to it that I'm not seeing, but knock isn't it.

PowerLabs

Yes, the heads were re-done with new Viton seals, a 5 angle valve job, new valves, new retainers, etc...
The ZR1 cam is a bone stock OEM camshaft, it doesn't have enough lift to ruin anything.

LME is not going to do anything about this; their stance is that it is normal...

5 Liter Eater

That looks really bad IMO. I dont see how that much carbon on the pistons or the scratches in the cylinder walls could be thought to be normal. I would take the pistons out, re-hone (depending on how deep those scratches really are) and re-ring it. Maybe you can get the builder to do that for fairly cheap if you still want to deal with them.

Can you feel those scratches with your fingernail? Any oil in your catch can?

SBCGENII

I'm lost you said it wasn't the compression ratio, cam, or tune, or the builders fault for an abnormal amount of oil on the piston. The only thing left is you.

1. if you pulled all the plugs when you did the compression test and spun it enough to get a good reading you A. rings where not worn in properly. B not installed with the right clearance's. C the cam isn't right.

2. That much oil will cause knock, not the tuners fault, timming might be pulled in a table You cant see.

Your long block is messed up! Weak compression, scoring on the cylinder walls and oil all over the pistons. Maybe the compression is do to the cam, maybe. Or is it do to the poor ring seal? I Wouldn't use break in oil in a roller cam motor cause all i care about is getting the rings to seat. I have seen people not break a motor in correct "flat tappet" and they wondered why the dipstick tube kept blowing out. Maybe you could measure your crankcase pressure and it would give you a headsup to to and your builder whats going on.

knkali

so to summarize so far:

All gear heads on this thread are saying something is wrong based on the appearance of the pistons. Sam is saying that the piston look is do to the low compression of the motor which nobody has disputed as a possible cause. Is this a fair synopsis?

Therefore if Sam increases the compression all should be good. If not then there is more to this story. Correct?

Makes sense. Sam is doing everything possible in an effort to not have to r and r the motor. So if he bumps comp and fuel mileage goes up, HP goes up, torque goes up, and the piston faces look clean, problem solved. He has nothing to lose trying this approach.

tjwong

This guy had an issue with LME to, his pistons looks striking similar to yours, using oil at a rate of 2+ quarts every 1k miles

http://forums.corvetteforum.com/c6-c...l-engines.html

No I don't beleive the build up on his pistons is due to the pistons compression ratio, in the link above that persons pistons were 11.3:1 in a LS7 build. That engine issue was long resolved if you read the complete thread.

PowerLabs

No, I did not say or imply any of that. The pistons look like they are seeing burning oil. If I increase the compression power will go up. This would be true even if one of the pistons was split in half.

The bottom line is simple: I spent $7k on this engine and another $7K on top of that getting my car back together (new clutch, new blower, new intercooler, meth kit, transmission rebuild and other misc. stuff). I spent 14 thousand dollars to get less fuel economy, 50 ft-lbs less torque, and 20 more hp., although that extra power is largely because I now have a car that won't run right unless I periodically refill a tank on the back with 100% pure methanol, which is oh-so-convenient for my usage which involves 3000+ mile road trips...

I have quite simply ran out of money, time and patience to continue taking my car (my only car) out of the road in the middle of the summer, tearing it apart late at night after work and during the weekends when I could be doing something else, and then blowing money away on it that I will never get back. I am going to up the compression ratio because it will run better that way. I will drive it like that for another year or so, then sell it.
And probably never pay someone to build me an engine again after that.
This has been the most disappointing project I've ever been involved in.

I won't blame LME: their stance is nothing is wrong. Each one of you can make your own decision regarding that; assigning blame is not going to fix anything.