i had a ls/vtec in my crx one time. everything put together was brand new. oil pumptoo but oil pump was bad from the get go. so upon start up it starved cylinder 1 for oil and spun the rodbearing just a little bit. enough to make it knock on start up but it then quieted after 10 secs or so. i drove it around like that for months putting a new oil pump on by the way. so you may want to pull the oil pan off and check rod bearing before you committ to buying something that may need to be replaced.

 

i was doing ok til i read that ugh

 

The knock should not be audible from inside the car... Especially when you are moving.

The noise you would expect from a forged piston is also different based on the type of piston used... They have different silicone contents. Basically, the higher the silicone content of the piston the less noise it will make, but it will not hold up as well to ultra-high EGT's created from very high cylinder pressures.