[Amc-list] 390 vs. 401 crank casting numbers

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Yes, AMC do have weighted dampeners and flexplate/flywheels.  Thinking it is ok to interchange them without checking the balance on a new engine is just poor engine building though.  The balance of an engine can be the difference between it lasting 1000 miles and 100,000 miles.  Anytime you change out parts like pistons, rods, cranks... in an engine build, you should always re-balance the rotating assembly.  Is it safe to take a 401 dampener off of one engine to put on a another running engine?  Well, yeah for the most part on a factory untouched unit.  But even the factory parts are different.  Want proof, look at your balancer.  You will notice drill marks in it.  No two are exactly the same.  Now, not knowing where that balancer had been, it might be set up for a heavier piston combo or a lighter set.  Again, always best when putting an engine together, especially if there is new parts in the rotating assembly, to re-balance
 the entire rotating mass.  You will get a much smoother running engine that will last much longer than if you don't.

As for Greg's issue, sorry to hear that Greg.  Stinks to find out the crank you had wasn't what you set up all your parts for.  Be careful with the pistons I made for you.  I know you said you are going to mill them now to get them to work.  Doesn't sound like you will taking off enough to interfere with the valves but check clearance just to be safe.  Flame travel and quench area should still ok as well.

Nick
Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends 
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