Hello all!

First off, the knowledge in these forums is priceless! A plethora of info around here!

Well, to get directly on it, I believe this 3800 SC motor has a rod knocking.

My story -

Recently purchased this '03 GTP from a used car dealership less than 1k miles ago.

The car has 2 previous owners, 100k miles on it, and was $4900. Seemed like a good deal, so I slapped down the greenbacks...

I immediately did a fluid change. The oil looked rough, so I replaced the oil with Mobile 1 10w30, and a k&n oil filter.

The CEL came on with-in 300 miles of driving the car...I forget the number it threw, but turned out to be a bad thermostat...Replaced that with fluids as well.

I noticed a bad tensioner bearing on the acc belt, so I replaced both belts, both tensioner pullies, and the SC idler pulley...

I've also replaced the radiator cap and air filter fwiw...

I was getting around to servicing the plugs, and noticed the motor resonating a tap tap tap sound from the passenger side of the engine.

What is strange though is when I stand over the motor I don't hear it as much as when I stand about 4ft away from it.

I have been reading about "piston slap", but I might be kidding myself into believing it's that..

I have also read somewhere something about the harmonic balancer going bad making things wobble around down there.

The knocking seems to vary with RPMs. If I just flick on the throttle cable, I hear the knock fade out then resonate back...

With it idling, the tap seems to have a pattern to it - tap tap tap ----- smooth ---- tap tap tap ---- ect ---

I'm also thinking the motor mounts are shot...The motor seems to twitch around in the engine bay at idle. I haven't had much luck with solid motor mounts, so those I'll pass on...
Are there any nice sets the gurus can recommend?

I've also purchased a tranny filter and seal (Auto)... Any advice on performing this service?
Looks like Dexron VI is the way to go, correct?

Should I pull the plugs and inspect each one?

I don't mind replacing the block and pistons, are there any vendors to recommend on a remaned short block? Could I take a N/A block/pistons and swap it in? (Still new to GPs and blowers)

I plan on keeping it stock with regular maintenance and 91 octane.

Here are a few vids of the motor and the knock sound -

YouTube - CIMG3926.AVI

YouTube - CIMG3928.AVI

Here is another video of the motor "missing" at a high rev (not sure if this is normal) -

YouTube - CIMG3927.AVI

Glad to have found these forums, looks like a good place...

Thanks much for any thoughts/replys/advice!!