Will my 290 manual flex plate fit a 401 and be balanced okay

[hogman]

I have a flex plate from a 290 cu. in. motor with a manual trans. Will that fit a 401 that had an automatic okay?

[tufcj]

NO.

All Gen2 and Gen3 AMC V-8s are externally balanced. The harmonic balancer and flywheel/flexplate are displacement specific. You will need a 401 flywheel/flexplate.

Also, the crankshaft flanges are different (unless you have a 71 401). The 290 flywheel won't fit over the flange of the 72-up crank.

Bob
tufcj

[hogman]

Thank you Bob! I have a lot to learn but thankfully there are many forums on AMC motors.

[Wrench Man]

And manual transmissions don't use flexplate's, they use flywheels.