6.5" Olds V8 350/400/403/425/455 Harmonic Damper 80022

Oldsmobile Harmonic Damper 6.5" V8 350/400/403/425/455. This is an externally balanced damper with a bolt-in counterweight which can be removed for a neutral balanced rotating assembly. This damper will work on 330/350/400/403/425/455 cubic inch Old's engines. The damper features the stock Old's accessory pulley bolt pattern as well as a Big Block Chevy bolt pattern for those who may want to run a crank trigger system. Use of Chevy pulleys will require some machining to damper. Note: On 330 engines, TDC mark must be repositioned. This damper fits late 400 and 425 only. Early 400/425 engines have a different counterbalance than provided. A good balance shop can modify counterbalance to work correctly on early 400 or 425 engines.

In order to assure a proper fit of your stock accessory pulleys to this damper, the four mounting holes in your pulley have to be drilled out using any one of the following three 
drill sizes: 
Letter Size Drill "T" 
Fractional Size Drill 23/64" 
Metric Size Drill 9MM 
**Any of the three size drills will work