All...Here's my latest regarding my piston slap and the "tapping noise" at 1440-1800rpm, the latter I most concerned about. My initial post "In denial---No more" yielded a lot of very important info. It got me thinking a little more of whatreally is going on. The cold start noise doesn't really bother me. I will take it in to the dealer and register my concern if only to get it in the system in the eventof a recall or TSB. The concern I had regarding the noise during acceleration if I hold first or second gear (A4) at between 1400-1800rpm is there all the time. I had the time to go for a long ride yesterday and check oil pressure and oil/coolant temps and everything seems to be withing normal ranges and the cold piston slap noise goes away very quickly after initial startup. It lasts only a few minutes as temps increase.
The other noise (1400-1800rpm) was there after a two hour ride and was very evident revving in neutral in my garage. It seems to come from the passenger side front of the engine and sounds like some sort of pulley mechanism or my a valve of some sort. It's there on acceleration and deceleration which almost makes me believe it is some sort of resonance.
I now do not believe it is related to the powertrain. I think it is an external component. This makes me feel somewhat relieved. Today's weather is still sunny so I will get my home-made stethoscope out and have my buddy rev it up and I'll try to pinpoint the source. I had the opportunity to "exercise" my baby yesterday for the first since I installed the Corsa Indy's and Blackwing, and I am impressed...Not to mention a few dozen other highway travelers.
More to come...I'll let y'all know...GeorgeC :flag :flag :flag

 

George,

I think that the oil consumption issue and the piston slap issue are closely related so I'm pasting the TSB for oil consumption.

I was a little surprised to read that the TSB states to not bore the engine because the GM rep was all over wanting to bore my engine 1 over and put in hand fitted piston's. Another note was when I brought up the oil consuption issue he started a speil about piston slap and how some pistons got put in below tollerence and they would check and correct.

My service ticket showed the piston to cylinder wall clearance was .004 which is double the acceptable clearance of .002.


TSB #01-06-01-023
Higher Than Expected Oil Consumption (Replace Rings)
1999-2001 Chevrolet Camaro, Corvette, 1999-2001 Pontiac Firebird with 5.7L Engine (VINs G, S -- RPOs LS1, LS6)
Condition
Some owners may comment on higher than expected oil consumption. When checked, the oil consumption could be in the range of 400-600 miles per quart (700-1000 km/L).
Cause
The cause for this condition may be an interaction between the piston rings and the cylinder bore in vehicles that are operated at higher RPMs -- typically manual transmission vehicles driven in a manner where the engine is frequently or consistently operating at greater than 3200 RPM.
Correction
A new set of piston rings is currently available through GMSPO. The new rings are part of a complete piston ring kit. Install only the number 2 compression ring and the oil expander ring from the piston ring kit. All other rings in the piston ring kit should be discarded. The original number 1 compression ring and the oil ring rails should be re-used in their original positions on the piston. All pistons should be used in the same cylinder bore.
Important
Do not dress or hone the cylinder bore. Nothing should be done to change the bore finish for this condition. Changing the bore finish may aggravate the condition.
Refer to the Unit Repair Manual for appropriate ring removal and replacement procedure.
The number 1 compression ring and the upper and lower oil expander rails are re-used because they are already broken in for the bore that they are in. The new number 2 compression ring is made with a very sharp edge that will break in quickly.
Changing only the piston rings noted, with no change in driving style, should change oil consumption to an acceptable level. Changes in driving style that reduce the amount of time spent at higher RPMs will also positively effect oil consumption.
In addition to the standard size piston ring kit listed below, a 0.25 mm oversized piston ring kit is available. The oversized piston ring kit should only be used in those rare instances where the cylinder bore size has been machined larger to accommodate the 0.25 mm oversized piston rings.

 

Here's yet another installment...Yesterday morning I got my stethoscope out
and got my girlfriend into the car to do some diagnostics. Started up cold and
heard some normal cold engine sounds. Couldn't tell exactly where it came from but the scope (actually a length of hose) on the block and heads sounded quiet. After a minute or two and what sounded like some solenoids switching off/on and the idle coming down, it was very quiet. I stated earlier that this other noise (revving or drive between 1400-1800rpm) sounded like piston slap or whatever and sounded like it came from the front of the engine was still there. With the scope, I couldn't pinpoint anything on the front. Because I have a full carbon fiber engine cover, I had to remove it. Started up again and with the scope (hose) I could now hear the injectors clattering away quite distinctly. I guess the engine cover diverted the sound out towards the front. The scope on the heads and block (as far as I could reach) was whisper quiet and the sound on two injectors on the right side where significantly louder than the others. One on the left side was slightly louder. So somewhere in that RPM range these injectors really scream. The car runs very strong and doesn't seem to miss, however, I do get some engine roughness at idle at times. A question is: Do the injectors fire even during decleration? Because they clatter revving up and down? Is there a tolerance spec on noise or is it just a random thing. I do feel very relieved that I could pinpoint the source. I should have listened to the tech who helped me with my exhaust install. I let him listen and he immediately said "All I hear are the injectors." Do you suggest having the dealer change injectors?...Under warranty of course.
Any other input? ...George :flag

 

Oh, BTW...Oil consumption doesn't seem to be an issue...1500 miles since last change and it's exactly where it was. Unless I had consumption greater than 1quart/1000 miles, I don't believe I would worry about it.

 

What does piston slap sound like??

What if the knock sound doesn't go away or is still there a little after warm up?

 

I just came up from a C4 to a C5 and the injector "ticking" on the C4 was very evident on the L-98. When I first bought the car, I thought it was a lifter problem. In the end, I got used to it. Last year, I ended up changing the injectors to RC Engineering injectors which are a different design. They were not as loud as the original injectors. If you are convinced that the block is OK and it is truly the injectors, I would take it in and register a complaint. They may not change them, but at least it will be on record if one gives up the ghost. As far as decceleration, I don't believe the injectors are fired because you don't want a large fuel build-up in the cylinder, but I am not positive about this.

 

I had the injector tick and the piston slap on my old LT1 '97 Trans Am. I thought the injector sound was a lifter problem as well until I got with some Chevy techs and we diagnosed the problem. I haven't heard any injector sounds that are out of the ordinary on the 'Vette, though.

 

Hey 'Nuts...My guess that the injectors do open occassionally during decceleration as the carbs used to as well. It's not a full squirt because
that's dumping raw gas into the cylinder but a lower rate burn keeps
the engine smoother. Just a guess though...George