dirtydiaper

i have a 1993 silverado c1500 4.3 v6 vin z...... it has a knocking sound that sounds like its comming from under the intake. it does not do it when cold, only when it warms up at idle. it will go away if i hold the trottle at maybe 1/4 throttle. if i give it more it will start knocking again. and when i drive it at 50 mph it does not knock until i start slowing down for a stop sign or light. i had the rocker covers off and the rockers and push rods seemed fine. i tried putting pressure on each rocker to see if there would be a difference and there was no change on any of the rockers, so the only thing i believe it could be is a lifter or piston pin....?

also i am thinking about taking the 4.3 out and dropping in a 305 or 350. will a 305 or 350 bolt right up to the trans and motor mounts that are already in the truck? i dont know what trans it has. the truck is a standard cab short bed. thanks in advance for any and all help

Cpb200

if i was you i would redo the trans if your going to put a bigger motor the 305 should bolt up