SFI fluid damper for 4.0

[Plechtan]

I have heard about people bushing a Big Block chevy damper for use on the Jeep. The Crank is only 1.125" diameter. this is much smaller than most all v8 engines. The other issuse is the OD of the hub, only about 1.78" This is the size you need to go through the seal in the timing chain cover.

The SB chevy is about 1.250 ID, so about 1/8" too big. By the time you payed a machine shop to put a bushing in and cut a new keyway, you would probably be better buying a performance unit.

[Mgardiner1]

I guess i was looking for a little more information on what "performance" units are available. After 15 min of google-ing i only could come up with stock dampers, or performance dampers for other applications

[Plechtan]

I think a Honda balancer could be made to work. The honda has 3 pulleys on it so it would stick out a little further. Any performance ballancer with a removable hub could be made to work. The names that come to mind are TCI ( "rattler"), Fluiddamper, and ATI. I bought athe ATI becuse they had a part number for a 4.0 and i liked the technology they used. It could be that the other companies make one for the 4.0 but do not have it in the catalog. TCI has a form on their site for a custom damper.

Maybe you should give them a call to see if they have somthing available.

[crustodd]

I must interject with a "fool" question. Does this replace a part that our engines already have? What do you gain by adding this if the 6 doesn't already have it? Aren't our engines internally balanced?

[Plechtan]

Good question, I guess you could ask why people change fuel injector to larger sizes, or change cams, throw away factory timing chains and put double roller setups on. The engine comes with all of these things from the factory, just use the factory stuff.

The damper or harmonic balancer is designed to remove or dampen harmonics that occur in the engine. the main source of these vibrations is the twisting of the crankshaft when a piston fires. Newtons first law ( a body in motion tends to stay in motion) tell us that the crankshaft and flywheel will not immediately accelerate, so when the piston fires, it puts an extreme force in a very small area of the crank, since there is much less mass on the front of the crank, it is easier to accelerate than the rear of the crank and flywheel. at some point the force on the piston goes away and the twist goes out of the crank.

The amount of twist would be related to the force applied, a stroker motor can usually output 25% to 50% more HP and torque than a stock engine. Since the vibration produced are more violent then the stock damper is designed to handle, it does not do the best job.

Dampers serve an important function. A market for them would not exist if they were not necessary. besides the dampening function, the performance balancers are usually SFI rated. the stock dampers can come apart under extreme conditions.