I have a marble in a can sound when I'm going real light on the throttle and the engine is under load like when going up a hill or something is this Ping? And if it is ping how do I stop it?

Thanks'

 

Yep. that's exactly what it sounds like. You need to check your plenum, and see if the gasket it blown. (sure sounds like it.)

 

This is not my video, but the pinging starts at 3:47

http://www.youtube.com/watch?v=JuY3CICc70Q

 

use a higher octane fuel and it will go away, but your plenum gasket is prob shot

 

I thought a header leak was pinging. I should have known because the sound was uniform. Pinging is very erratic. Almost like random rattling.

 

And if you have a CAT on your truck, it's probably plugged as well.

 

How hard on a motor is it to let it ping? Mine does just what the O.P truck is doing. Will it mess up my motor if I let it ping till spring when I can change the plenum gasket? I have it all and just need to finish cutting the intake.

 

Ping is also known as "Pre-Ignition". Your cylinders firing BEFORE the plug actually fires it. Possible consequences include, but, are not limited to: Broken pistons. Melted pistons. Bent Rods. Etc. All VERY expensive repairs. You might be able to slide by using a higher octane fuel, but, fixing the root cause of the problem is your best bet.

 

I've never actually heard of an engine being ruined by pinging, but it can't be happy about it. After all, the pinging is caused by the flame front hitting the pistons while they're still on the way up. It's my understanding that the sound is caused by the rattling of the piston/wrist pin connection. You might want to run premium gas until you can eliminate the cause of the pinging, and/or try to retard the timing a little by moving the crankshaft position sensor a little. I've read a few threads on here about slotting the CKPS bracket so you can move it a couple of degrees.

Question: You mention that you have a 25% underdrive pulley. I associate those with superchargers. You got a blower on that thing? If not, what's the purpose of an underdrive pulley? My best guess would be to reduce the amount of power used by the fan.

 

Just to keep things from getting confusing, it's my understanding that pinging can occur without the type of "pre-ignition" you're referring to, where typically a red-hot chunk of carbon build-up ignites the air-fuel mixture before the spark plug has a chance to. I think it can also occur when the plug ignites the mixture a little too soon. As always, please correct me if I'm wrong.