340 rapping at 2200 rpm

[Rockboyz]

Gents,
Took the hot rod out for a few trips over the holiday weekend, the most I've driven it all year. Starting hearing a raping noise at 2200-2300 rpm under a very light load. Basically cruising at 55mph. No noise lower or higher. Its not a "knocking" sound like a rod, and its not "ticking" like a lifter. Any ideas or things to check?

[jimynick]

Wrist pin or a piston skirt? What rpm range does it sustain to? Does it stay coming off or on an acceleration? Is the rapping at engine speed and does it speed up or slow down with engine speed or is it just rapping at 22-2300 rpm?

[Rockboyz]

I would say the "rap" seems to be at engine speed, however, since I can only hear it at that rpm, its pretty hard to tell if it increases or decreases. Ill need to drive it again to determine if its only on acceleration or deceleration as well. Thanks for the feedback

[Chryco Psycho]

It could be as simple as bad lifters not holding pressure & the valve train gets loose .

[73_Cuda_4_Me]

Does it sound like marbles clinking on slight acceleration at cruising speed? If so, then that indicates you are getting spark knock, or pre-detonation in cylinder as the piston is coming up in the bore, rather than just before TDC...

What size engine - small block, big block, and running headers?

What octane gas are you using, and are you running vacuum advance on the distributor?

What kind of cam are you running, and where is your initial timing set?