Steel/steel vs alloy/steel harmonic damper

[ToddK]

I'm looking to buy a new ATI harmonic damper for an engine I am putting together. It is a 496 cube motor that I hope to get about 750hp/7000rpm out of. For my past 2 engines, I have used the ATI part# 918310, which is a steel outer and inner damper. However, I just noticed ATI make a FE damper with an alloy outer shell and steel inner, which is actually cheaper than the steel/steel damper. Any disadvantage to using the alloy/steel damper for my application?

[jayb]

What are the weights of the two dampers?  I've been told that a good heavy damper is what you want for a high horsepower engine.  I assume the alloy is aluminum; is that damper much lighter than the other one?

[cjshaker]

Personally, I'd stay with the steel/steel unit. They're better at damping and less prone to heat and durability issues. I think the only reason for an aluminum one is for the guys who want to shave every ounce they can and lessen rotational weight which is probably pretty unrealistic for any gains. A strictly drag engine won't be in the vibration/harmonic cycles for very long, so negative effects are pretty minimal except for shorter life span.

ATI shows the aluminum hub to be a little over 2 1/2lbs lighter.

[ToddK]

The ATI catalog shows the aluminium shell damper to be about 1.5lbs lighter, but also lists it as having the same inertia weight as the steel unit. I'll probably just stay with the steel one I have used in the past.

[CaptCobrajet]

The need for "more" damper is most closely related to stroke.  As stroke increases, heavier inertia weights and larger diameters are more desireable.  I use alot of both styles of the ATI dampers.  On some short stroke FEs (like 3.5) we use a smaller diameter, and very light shell...........On long strokers (like 4.4) we use a larger and heavier unit.  I think the ATI's are the best..........JMO.  They have alot more options than what is listed in the catalog.

[Yellow Truck]

They ran aluminum hubs with iron alloy inertial rings on the GT40s. Probably good enough for the street.