FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: 338Raptor on June 26, 2019, 01:48:48 AM
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Which damper would best protect a 4.375” forged 4340 Scat crankshaft?
My application:
90% street, 5% drag, 5% autocross. Approx 3300# car, manual trans with aluminum flywheel.
526 cid SOHC, 800 hp, 700 tq, approx 7500 maximum RPM.
Which brands are best suited for my application and which should I avoid?
I assume I want something heavy and SFI approved.
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I would only consider ATI and IW, and would lean more heavily toward IW.
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Ask Kaase what he uses on his long arm monster motors
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I know that an IW will handle 1200 hp at 8500.
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If you go with the ATI, just be aware that it WILL be 7* off, so you'd need to alter or make a new pointer. Very nice piece, otherwise.
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I always use ATI, have had good luck with them. I would steer clear of Fluidampr, the Scat guys have told me that whenever they see a broken crank, there is a Fluidampr on the snout...
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IW nice parts but at least on a wedge the spacer sleeve must be reduced in length. Not a big deal but it is another step.
JB
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Jay, do you run the aluminum or the steel ATI on your big motor?
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I always use ATI, have had good luck with them. I would steer clear of Fluidampr, the Scat guys have told me that whenever they see a broken crank, there is a Fluidampr on the snout...
Fluidamprs are great, but I don't think they work well on high RPM stuff. On low rpm, trucks, diesels, they are hard to beat. It's funny because on high performance stuff I've seen broken cranks with viscous dampers, but in the heavy duty stuff most of the broken cranks were using bonded dampers (or they tried running a viscous damper 3 million miles and the silicone is as hard as a rock or someone dented the can).
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ATI
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After reading these comments I’m now a little worried. I have a Fluidampr on my 6700 RPM, 900 hp 557 with an Eagle 4340 4.5” crankshaft.
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After reading these comments I’m now a little worried. I have a Fluidampr on my 6700 RPM, 900 hp 557 with an Eagle 4340 4.5” crankshaft.
I would be too.
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Spend $400 to save a $10,000 engine? Heck yeah.
JMO,
paulie
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Jay, do you run the aluminum or the steel ATI on your big motor?
The steel one, you want a heavy damper with a big stroker crank.
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The chart here makes me believe you also need to a custom crank spacer shortened .375" to use the damper and then you also need an adapter to to install your OEM pulley in the correct location?
http://www.atiracing.com/products/dampers/charts/damford.htm
For instance, using damper 918310 (Steel, 7") says this: 1957-1961 early FE - Requires adapter #916581 & shortening the spacer sleeve .375”, to install stock pulleys in the OEM location.
All this damper talk makes me think it may be time to upgrade my Professional Products OEM replacement for my 428.
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I haven't needed to shorten the spacer with any aftermarket crank and timing setup I've used. For the pulleys, the bolt circle on the ATI damper is just slightly off from stock FE (I think its for a big block Chev maybe?). Anyway, all you have to do is open up the holes in the pulley to 7/16" with a drill, and it will bolt right on. No big deal.
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Current build is getting a Pro Products 9000 series. This is a short stroke under 5.5k rpm deal so it should live fine. Call me a tight wad for using it but I bought it at an estate auction for $2.50 still in the box, shelf wear but new. A factory replacement would probably also be fine but Its SFI approved so it makes me feel better. I do think Ive heard some mention to make sure and lock tight the hardware on these or they work loose and tear things up. Had to buy the new pointer to match, $13 seemed pricey compared to the dampener :D. It's nice they offer that and its nice quality too not to cheap and flimsy like some pointers are. Wish ATI would offer one or even better, correct the timing instead of force feeding us chevy parts adapted to work.
I was going to use an ATI but seemed like overkill after scoring the $2.50 deal so it's waiting on the shelf for a future build. Where I messed up at that sale was a on used comp roller and lifters that sold for about the same amount.. The cam was way big really unusable for anything I needed didn't dawn on me to have it reground till it was too late. :-[
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I used a Romac. The timing marks were spot on and I didn't need to drill out the pulley holes. I'm very happy with it.
http://www.romacusa.com/products.html (http://www.romacusa.com/products.html)
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I believe Barry recommends Romac units in his book, if I'm remembering correctly.
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I must be old school. I am running a C6AE-6316-A 428 PI damper that looks like the 427 damper except for the edge bevel and timing marks and an aluminum flywheel that was balanced with my engine. The damper was an NOS item and there is no issues with the rubber. Damn thing must weigh 20 lbs.
-Keith