Engine Vibration 2500-3000 RPM
I have been chasing this vibration down for almost a year now. I have done countless searches and done everything suggested in those posts but cannot seem to find this vibration. A little background, the engine is the 290hp GM Performance Parts 350ci and it is showing this vibration between 2500 and 3000 RPM in park, so that eliminates the trans and remaining driveline. So far, I have replaced all pulleys, bought and installed a new ATI balancer, checked the runout on the crank snout, pulled plugs while engine was at vibration rpm and all plugs caused a drop in rpm. This vibration happens while accelerating and decelerating, so I'm hoping this can eliminate timing/carburetor issues. So I have now moved to the rear of the engine and removed the transmission and clutch and am still getting the vibration. Does anyone have any suggestions on what I could do next? The flywheel is stamped GM and 3973456N which looks like a neutral balanced flywheel (per Google) and there are no weights on it. Can a flywheel go out of balance?
1967 Camaro RS
GMPP 350 c.i. (soon to be aluminum head 355 when the machine shop is done!)
M-20 Muncie 4-spd
12-bolt 3.55s (4.10s were too much)
Hugger Orange w/Black Z/28 stripes