i have a 1990 454 chevy boat runs fine till i hit 2800 rpm then starts poping and cracking and runs like crap has anyone any ideas why ?has a holley 4 barrel and i replaced power valves but didnt help problem

Bad Fuel ?
Valve spring broke?
Sparkplug issue?
Ignition Issue?
Process of elimination

bad fuel bad plugs, dirty carb or air filter. After that I dont know

sounds more like ignition or possibly running out of fuel....need to ck fuel pressure at speed....

did you find the problem? if not i would start checking under the valve covers. make sure rockers are moving right. had a cam wear down and did the same thing

Had the same problem, was a flat cam lobe... check rocker movement.

Just Toasted A Brand New Engine Cause The Builder Seemingly Somehow Or Another Allowed One Of The Retainers On The Valve Spring To Fail. Lost The Entire Engine Over It With Mechanic On Board For Dialing In The Engine, Gues You Cant Get One To Stop Turning Quick Enough. Id Listen To The Elders On Here They Seem Knowledgable.

Sounds like a bad cam lobe or stuck valve to me also.

mine did the same thing your sayin and i put a new coil on and mine was fine.. if that doesnt work i know my buddies was doing it to , he replaced coil and it still did it, so he replaced the cap and it was fine.. hope this helps

make sure floats areadjusted properly, and floats are working properly. My 4 barrel the rear float was bent..