Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I've never heard that about the L-82 of any year, but I s'pose it's possible. The C4 model L-98s are BAD slappers when cold...just a fact. Doesn't hurt anything on them, tho. Does yours only do it when cold, or does it have this noise all the time? IF all the time, does the noise change when it warms up, or stay the same? Does it sound like only one piston making the noise?
Piston "slap" is what happens if there is a little too much clearance between the piston and the cylinder bore. When the piston reaches TDC(top dead center) OR BTC(bottom dead center), it will rock in the bore, and create a noise as the piston barrel hits the bore wall...kinda like a diesel engine running, but not as loud, or constant. Most of the time, this doesn't hurt anything. If it is really bad, it could eventually break the piston.
____________________________________ Joel Adams C3VR Lifetime Member #56 My Link
Vette(s): 1981 Great White Shark. Red Interior, 350/190hp. PS, PB (SS), A/C CC, T-Tops, Going to remain as Stock as possible. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vetts Car Club. 175,000 Original miles!!
Are you sure it is piston slap and not a mechanical fuel pump noise?? That Luke guy up there ^ !! He stole my answer!!
Vette(s): 1975 C3 Red, T-Tops, Black Interior.
All I need is time and money! Getting there!
Even with a new fuel pump, it could be the fuel pump push rod. A worn rod will do this. Pinch the fuel pump suction line for a minute or two. If the noise stops before you run out of fuel, replace the rod. Still could be a piston.
will try pinching the fuel line at the pump.....and the heat riser isnt coming into play i dont think...it was disconected when i bougt the car.....and its frozen open.....kinda stumped with this....i work in a new car dealership and have my techs do the work on my vette....one of them was with chevy in the late 70s....he says just drive the car....its nothing to worry about...oil pressure is good....car has plenty of power....only has 32 thousand miles on it
Vette(s): 1971 350 270 hp roadster millivanilli red, black interior, white rag top, white hard top, I've had it 18 years and intend on giving it to my son for his 25th birthday(another 18 years from now)
Rut roh sounds like carbon knock to me ....but there is a good remedy for this.Pull all the plugs and get some EOS at the gm dealer,fill all the spark plug holes with it and let it sit for 72 hours and then turn the motor over with the plugs out(it will be messy) put an old set of plugs in and let the motor warm up and then go hammer on it for a while put the fresh plugs back in and you should be in good shape
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