Gen 6 454, just converted to carb. alum. manifold, new elec. fuel pump, accell hei dist. when timing set at 4 BTC and vacuum advance hooked to timed port on edelbrock carb a spark knock is heard around 1500/2000 rpm. have adjusted the vacuum advance at dist. and no change. no knock at acceleration just when light throttle pressure. tried to use full vacuum port on carb and seems to be worse. 89/92 octane....any ideas what i'm doing wrong? running out of ideas. thanks for any help, Mike

 

What compression ratio does that motor have? Im thinkin the fuel is pre detonating.

 

Not sure on the comp ration. vortec short block from the numbers i have. not sure on the cam either. no knock before the swap so i'm still thinking timing/advance issue. going to change to stiffer springs in the distr. tomorrow and maybe change weights. had a suggestion sent to me that was the problem. if advancing to soon spark knock is possible under light throttle but will go away when rpm are increased. sounds reasonable since the motor was quiet before. thanks for the reply RUFFNECK.