I've decided to buy a new damper for my 434 build and have narrowed it down to ATI and Innovators West. The engine is a pump gas street/strip deal, with a comp solid roller. It should be in the 650-675 HP range and 7000 rpm max, peak power should be in the 6400-6500 rpm range.

Today I called ATI and they recommended an aluminum outer three ring that weighs 10.75#. The Innovators West damper weighs 8.2#.

Light or heavy? I really hate to have to deal with the extra .450" that the ATI will move the pulley out as I'm close to the radiator with it in the factory location.

Thanks.

I have an aluminum shell ATI damper for sale in the SB section that should work. I bought it for a 427 stroker motor but ended up using something else.

I would use the IW or a Fluidamper. Ma spent a buttload of reseach money on dampners over the years. Their R&D showed the FD to be best.

All that said, ATI markets their stuff well enough that facts don't always matter, but when you call their tech department and they tell you bob weight and RPM doesn't matter in rubber durometer (and other things) I decided that I would skip that nonsense.

I would certainly spend some more time looking into what makes a part like that work, why Chryslers almost never failed a crank when GM was having issues. Sometimes, dampner weight (as in being too heavy) is not a bad thing, specifically when you are talking about elastomer (rubber) types. Moroso (and some others) were 100% responsible for the mass crank failures that occured when NHRA mandated spec dampners. Everyone jumped on the "light is right and fastest" band wagon and paid for it with busted cranks.

Andy I saw your damper last night and was the reason I called ATI this AM. Their tech said with the rpm I was planning on turning and driving on the street he would not recommend one that light.

IW told me they would build their damper specific to my engine, plus no pulley alignment issues.

Thanks guys.

Okay, sounds good. The damper I have was what ATI recommended for a 427 SB that was street driven and road raced so I figured it would be close for your application also but sounds like they think you would be better with the three ring. The one I have is only 7.5 lbs so it might be more suited for a drag race engine.

FWIW, the factory BB HP dampers were heavier than the LP ones and 426 Hemi dampers even heavier. Now think about the expected engine speed range they were designed for.

That's the point I was trying to make Nemesis, but you said it better than I did.

While there is more to the equation than just weight, especially when it comes to rubber band style dampners. Lightweight always sounds good but it isn't always.

The total weight (talking rubber band style here), durometer of the rubber, thickness of the rubber, width of the rubber, overall diameter of the balancer, even the difference of weight between the hub and the outer ring all affect damnper funtion.

As I wrote earlier, stroke length, bob weight, RPM and even available room all go into designing a dampner. Almost always, a bigger dampner is better, but it has to fit, so compromises are made.


As a last thought here...500cc single cylider two stroke engines are balanced at a relative high overbalance. This is done so that at higher engine speeds the engine gets very smooth, BUT, they shake like a dog poopin' peach seeds at idle. It's one of those compromises. A friend has a 2T guru do a CR 500 for him years ago. This guy was all that and a bag of chips. I was there when he fired it up for the first time. At idle, it was smooth as butter. I told him it was junk. He got butthurt and said I was stupid and jealous. The next day, we went for a ride. He lasted 20 minutes and gave up. Every time he opend the throttle the thing would vibrate so bad the handle bars felt like they were 10 inches in diamter and he said it was like riding a 240 pound jack hammer. Lesson learned.

So the moral of the story is do your research, never trust the first guy who answers the phone at big companies and never believe Madison Avenue types.

From what I was told by IW it's not all about the weight of the damper. The tech told me they had different friction packages that they used in their dampers depending on the combination.

Yup, that's pretty much what I'm trying to say...you can't always go by overall weight.

In my simple understanding, in order to dampen the vibrations inherent in a flexing crankshaft (they all flex) you have to convert on form of energy to another. From my limited knowledge, most of the dampners today convert the vibrations to heat and then dissipate that heat (sort of how a brake system functions). So, whether it's done through rubber bands, friction plates (think Ducati dry clutch or an old CZ dirt bike) or through shearing a fluid or a mechanical system like the Rattler (which I have never really looked into) you are trying to change one form of energy into another.

The rub is how effective each system is, how broad an RPM range each one is limited to, which naturally also will dictate how to size something like a dampner.

IIRC, I was told back in the early 90's that the rubber band (elastomer) style dampner had the narrowest frequency range and a relatively narrow RPM range compared to other types. But, it was the least expensive to design and build.

It is actually a fascinating study to do. In fact, I had an engineer on the phone from a well funded team and we were discussing different types of dampners. He told me that his particular team has not dyno tested dampners in the last 15 years. They also did all their dampner stuff in house.

Thanks, I'll order the IW tomorrow.

Ordered the Innovators West today, it should be here sometime next week.