Garibaldi

Okay.
I read the archives and there's contradictory info about oil consumption and piston slap. I tend to over maintain my cars but not sweat about small stuff. This is what my '00 FHC with 25k miles has:

--fairly consistent 'ticking' on startup (doesn't sound like a diesel; more like an old 911)
--loses a quart of oil every 2k miles
--completely black/sooty exhaust (my Contour SVT never gets at all dirty)
--Doesn't blow smoke when I hammer it
--Idles, runs fine

Problem? No problem?
****? Not ****?

Regards,
Garibaldi

Rattler71

The ticking could just be some carbon buildup. Mine had that and after a dyno tune(several times to rev limiter) it blew it all out and no more ticking. The oil consumption could be ring or pcv related. I know there were some ring problems with 2001's, don't know about 2000's. Mine is a 2000 with 50,000 miles but has no oil burning issues yet.

Scott

Patches

Here's a good article about it.

Hib Halverson's article at idavette.net

MikeyD

Can you have piston slap but no oil consumption? My 2000 uses no oil at all. I can go 3,000 miles and there is no drop on the oil dip stick whatsoever. I do, however, have a ticking noise, almost a diesel sound in fact.

Garibaldi

I read this article and many of the threads about oil consumption and piston slap. I'm trying to sort out the info to determine whether the combination of oil consumption, black exhaust, and ticking are good indications that my '00 FHC probably has piston slap/bad rings.

I'd like to get all my duckies in a row before I 'discuss' this issue at the dealer.

Regards.
Garibaldi

coreyd

If you don't have oil on the dip stick you most definately have oil consumption! might explain your diesel sound effects.

johnC5

Scott, was your car running rich before the dyno tune? That might explain the carbon build up with no oil consumption.

Burning oil can lead to carbon build up, which could lead to carbon knock. A decarb procedure can temporarily remedy it (until carbon builds up again). Shouldn't burn any appreciable amount of oil between changes (unless the oil gets extremely hot and vaporizes, such as track use).

You can check for piston slap by hooking up a Tech II or similar device (dealer has one), and cutting fuel to each cylinder, one by one. If the noise changes or goes away, it's likely piston slap.

cire96

Scott:
As an owner of a Mallett 435, I have cold engine piston slap. Therefore I know what it sounds like. If what you have a sound like a valve that's pecking BUT it goes away after the engine's thoroughly warmed (as in 15- 30 minutes) it's almost certainly piston slap. If it goes away in a under a minute or two, it's likely something else.

Piston slap is the noise that a piston can make as it transitions through top dead center when it tries to rock ... and if it's loose in the bore, the skirt of the piston "slaps" the cylinder wall.

Slapping and oil burning aren't particularly a hand in hand thing, since the rings will likely seal the walls and wipe down the excess oil. Oil buring occurs either because the cylinder bore is worn oversize, or the rings are worn (or have lost elasticity) and aren't wiping down the walls of the excess oil that's there.

When the piston heats up and therefore expands, the piston skirt fills the bore more tightly and the slap normally goes away (or diminsihes a lot).
...All for your info.
Cire

johnC5

The stock engines have hypereutectic pistons (very hard AlSi, don't expand much), whereas a Mallett 435 appears to have "custom forged aluminum Wiseco pistons with ceramic thermal-barrier and anti-friction coatings" which expand more than the stock pistons, requiring more cold clearance (and thus more noise at cold start up). However, once forged pistons are warmed up, there should be no noise (I recently spoke with an engine builder about forged pistons and piston slap, and he stated that Wiseco's were one of the better alloys that did not have significant piston slap issues. When was your engine built?).

Piston slap occurs in various (wear/tolerance) levels, based on the amount of extra space between the piston(s) and cylinder wall(s). Oil consumption likely occurs as the rings will not fully seat against the cylinder wall as the piston rotates in the bore (similar to a throttle plate (disk) opening and closing). Additionally, cylinder wall scoring is a common side effect of piston slap. Once the cylinder is scored, the rings cannot stop oil loss.

An engine with minor piston slap that goes away once warmed up may not use any appreciable amount of oil. If the noise continues once the engine is warm (less common, see videos below), the likelihood of oil consumption increases (greater amount of time piston is unstable due to secondary motion (piston slap)). If the noise goes away once warm and oil consumption is present, then cylinder wall scoring may be present, or the oil consumption occurs for another reason (PCV, intake, etc.).

Piston slap noise sounds much like a bad lifter:

http://www.brightland.com/cf/video/Z06Noise.wmv
http://www.brightland.com/cf/video/Z...WheelClose.mpg

Similar sound clip and photos of cylinder wall scoring here: http://www.pistonslap.com/photos.htm .
I've examined a 1999 LS1 with oil consumption and cylinder wall scoring, but without noticeable piston slap noise (most likely a manufacturing bore issue, not ring/piston design as not all 1999's (and pre new ring/piston design LSx's) exhibited this behavior. The new piston/ring design may reduce the probability of piston slap and oil consumption, but cannot handle extreme manufacturing build variance).

Rattler71

There is some confusion here. I was just answering his post about the oil consumption. My car uses no oil nor has any piston slap. It had a slight ticking noise I was explaining to the original poster which went away after the dyno tune.

But thanks for the responses!

Scott

phils C5 vette

I had oil consumption, and the dealer replaced my rings. I had a little piston slap and while the motor was apart the dealer said it was within tolerance, so I had them install my kooks and a GHL exhuast, and I dont hear any piston slip

cire96

John:
My 435 was built in 1998 and has 31,000 miles on it. Per Chuck Mallet, the coating on that era engine was not as swell as it might have been.

I have one piston that slaps until it's warmed. then it's quiet as a proverbial church mouse. Also, I've never experienced oil use (off the track that is).

I appreciate your comments re: forged pistons versus the stock units. I was only trying to give Scott the "cliff notes" version of piston slap since he seemed to be unclear what it was.
Cire

johnC5

Cire, thanks for the info. Older forged pistons were a bit noisier (cold start) than current forged pistons. My goal was to show that hypereutectic and modern forged pistons should be relatively quiet when built within specs. Sounds like the Wiseco's are a good forged piston.

Garibaldi

Sounds like piston slap is independent of oil consumption. What about consumption of 2k mi/qt and the sooty black exhaust? How much consumption is too much for a good running LS1? Two dealers and some forum members have said, "They all burn oil."

Regards,
Garibaldi

johnC5

I believe there have been posts as high as 7500 miles with no noticeable oil consumption for LSx engines. My threshold is no significant oil consumption between oil changes (3000-4000 miles). Three common ways an engine can lose oil:

1. Ring/piston/bore issues.
2. Intake/PCV issues.
3. Gasket/seal leaks.
4. High temperature vaporization (only extreme use / very high temps).

Perhaps the biggest problem of oil consumption is carbon build up:



Which leads to very poor fuel economy (abnormal combustion: pinging, detonation), with excess carbon build up on pistons causing carbon knock. Questions have been raised regarding decarb procedures and clogged catalytic converters (something to consider: when cats get clogged, what is the clogging agent?).

In summary, significant oil consumption is not a normal condition (1 quart in 2K miles is significant. I would consider ½ quart in 3000 miles borderline for a modern car not pushed to extremely high oil temps).

HHC5

With my 04 MN6 it sounds kinda like a diesel when I just start out in 1st....and today when I went from 1st to 4th at 1500 RPM's, I heard the diesel sound??? Just not sure what it is. Car has 600 miles on it. I hear it whether the engine is hot or cold---no difference. I don't hear anything at idle or while reving engine??

johnC5

If the noise is not heard while idling, it's not piston slap.

Did your car come with a VHS tape or DVD? The video describes a normal drivetrain noise that may describe what you heard.

HHC5

Nope--not a DVD or VHS. I don't think they offer them with the 2004's. There is a CD that I have not completely gone through yet.