[MPKind]

The 455 for my Catalina was rebuilt last April to correct the flywheel imbalance caused by retarded machine shop staff and company. See thread: "Tale of two flywheels".

Swapped the cam, upgraded to roller rockers, Rhoads V-Pro lifters to correct some top end issues...still not sure about the Rhoads, but that's for another time.

New billet steel flywheel (zero balance), and a stock LUK clutch, which finally improved the clutch and shifting action.

The entire rotating assembly was balanced. The old Eagle crankshaft I bought in 2008 had to be switched over from external balance to fully internal (zero front and back), the flywheel was not touched and along for the ride, but the two-piece 60s style Butler harmonic balancer was tweaked with some very small amounts of weight removed.

The new cam was broke in and it was ready to go, but there was still a vibration present. Granted it was not like before with a whacked flywheel, this time it was more isolated to an RPM range of 3000 to 4000 with maximum vibes around 3300+/-. It can be felt not moving, in neutral with clutch pedal in or out. More pronounced under a load going through the gears. It's not a severe vibration, but you can feel it enough to raise some concern.

The original build of the engine c.2010 was zero vibration to 5000 RPM+. I can't figure out why it's not better than this. One thing that crossed my mind was that my engine guy said he only used on piston/rod assembly to establish the bob weight for balancing being that it was balanced before. Also, if you convert an external balanced crankshaft to fully internal what other effects can occur? I'm sure it's been done many times with no adverse effects.

I drove the car all last summer and it performed well overall. I haven't talked to my engine guy about the vibration issues yet, but before I do I'd like to have some things to consider or discuss as to why this is happening.