Spark knock when cold?
 

Does anyone else have a bad ping under acceleration when the motor is cold. its defiantly spark knock b\c if I let out of the throttle its goes away and the more load the motor is under the louder it is. As soon as the motor warms up it goes away. Im running BP 93 fuel. Any ideas?

Re: Spark knock when cold?
 

It's probably what's refered to as piston "slap" or "rattle". When the engine is cold, the pistons don't fit snugly in the cylinders (now we're only talking .0001's of inches here). As they go up and down, the pistons bounce around a bit, and that's what makes the noise. As the piston heats up, it expands to fill the bores, and no longer "rattles".... and the noise goes away.

It's normal.

Re: Spark knock when cold?
 

It also a good idea to let you car warm up before you lean on it; oil at operating temperature is your friend :)

Re: Spark knock when cold?
 

If it was a rod, it would "knock" more under load. If it was detonation, the knock sensor would be taking care of it. Sounds serious.

Re: Spark knock when cold?
 

Rod knock wouldn't go away once the engine warms up.

Re: Spark knock when cold?
 

Humm...if it is piston slap would the knock sensor read that and retard the timing and lose power. The car runs great...It does need a new fuel check valve in the tank, it takes a wile to start but if i turnthe key on and off a few times it fires right up.

Im new to the chevy v8. I build drag bike motors and a lot of sport bikes and this motor is completely different. I feel like i need a computer degree to work on the thing. and the technology is archaic to me.


It almost sounds like the fuel injectors. I know they can make some noise but it that common on this motor

Re: Spark knock when cold?
 

Exhaust leak?

It's hard to guess when we can't hear it ;)