[Michael C Henry]

You're talking about an automatic flywheel ? The 428 was introduced in 1966 so was the C6 automatic transmission .1966 was the year they changed the starters and the number of teeth on the flywheels. I bought a 63 1/2 gallaxey with 428 and Cruis-O-Matic I had to replace the 428 right off the bat. Later i replaced the Cruis-O-Matic with a C6.That change required an off the shelf flywheel but a new custom made rear cross member. The 428 requires a n offset weighted flywheel. If your current flywheel has been adapted to a 428 the weights should be visable.Perhaps the home made weights are hitting something. To start off, which transmission are you using?