Damper Part # Diameter Timing Mark Position Timing Tab Information
6272221 6.75" 10 before crank keyway 12341904 or 12342000 Used on 1969 or later production 305 and 350
3817173 8" 2 before crank keyway 62 to 68 small journal 302-327. Casting # -2224
3947708 8" 2 before crank keyway   69 302 Z-28. Casting # -7708
6272224 8" 10 before crank keyway 12341915 or 12342011 70 to 74 350 Z-28. LT1, L82 and on ZZ3 350/345HP
6272225 8" 10 before crank keyway 1234191 70 to 80 externally balanced Gen. I 400
364709 8" 10 before crank keyway 1234191 HD, nodular iron, off-road racing, Has high temp elastormer rubber and is tuned for high-RPM operation. (8000RPM) Casting # -4709 and is marked "MALL" an abbrevation for malleable iron.
10051170 7.25" 2 before crank keyway   GM/Fluidamper is a viscous fluid damper for internally balanced smallblocks. This damper is accepted by many racing associations and dampens vibrations at all RPM. It has timing mark from TDC to 50. Weights 13.4 pounds.
10128489 Gen. II LT1 dual mass damper; use with hub (PN 12553250).
10225133       LT5 damper
12341632 6.25" 2 before crank keyway GM/Fluidamper weights 7.9 pounds and is for use on internally balanced engines.
14097258 6.75" 10 before crank keyway 1234190 Used with ZZ3 350/345HP crate engine with one-piece rear seal.
24502534 7" 2 before crank keyway GM/Performance Parts elastormer damper for internally balanced engines and standard size crank snout. This damper is tuned for high-RPM use (9000  RPM) and is similar to the ATI Super Damper. NASCAR approved and can be rebuilt by replacing the elastormer.
24502535 7" 2 before crank keyway   GM/Perfomance Parts elastormer damper for internally balanced smallblock engines with aftermarket crankshaft snouts sized to big block Chevy diameter (1.598") and is similar to the ATI Super Damper and GM damper (PN 24502534). NASCAR approved and can be rebuilt by replacing the elastormer.
Fluidamper does have a viscous fluid 8" damper for externally balanced 400s under Fluidampr (PN 712465).

Remember that if you are building a engine using a 400 crank and a 350 block to build the popular 383 combination, you must use a 400-style front vibration damper and a flywheel or flexplate for externally balanced 400 engines.

The crankshaft/front damper retaining bolt (PN 3815933) is 7/16"-20 x 2 1/4. The correct flat washer to use with this bolt is (PN 14001829 or 14092217).

Most race sanctioning bodies have banned the use of cast-iron production elastormer dampers on race engines for safety conciderations. You will need to use an SFI 18-1 approved specification damper such as the GM/Fluidampr or the ATI Super Damper types offered by GM/Performance Parts (PN 12402534 or 2450535).

Gen. II engine use a dual-mass vibration damper that is unique. THis damper and hub does not mate the crank snout in the manner most Gen. I smallblock enthusiasts are used to and consequently it can not be interchanged to Gen. I engines. THe dual-mass damper has two independent inertia rings mounted on a common hub, wich enables it to work over a wide range f engine RPM than previous designs. Rather than have a separate pulley for a sepentine belt, this damper incorporates the belt ribs and grooves as part of the damper. All Gen. II engines are externally balanced. All Gen. III engines are internally balanced and use a uniwue vibration damper.


Tommy Ledberg