Balancer specs

[K.O. SWINGER]

Hello guys, I just purchased a fluid balancer for my 340 s i f approved it seems like a bit of a hog coming in it 12.5 lb my car is currently not here and I would like to know the weight of the factory forge crank 340 harmonic balancer?

 

[yellow rose]

Weight has no bearing on crank balance or anything else. If you are externally balanced you need the weight that bolts to the damper.

Is yours a Fluidamper or a knock off?

 

[K.O. SWINGER]

Knock off, speed master. I just hate adding weight to my reciprocating unit! It goes against everything I believe LOL

 

[K.O. SWINGER]

After a little more research I found that factory 340 forged crank dampeners come in around 8 lb. So I'm not crazy about hooking another 4 lb onto the end of my crankshaft but for 340 that will see north of 7,000 RPM I think it's a route to go.

 

[33IMP]

I wouldnt worry about it, its not reciprocating weight, its just rotating. Very slightly harder to accelerate, probably impossible to measure, and if it does a better job of removing the harmonics.....? (which is its most important job).
You can probably get that four pounds back on the other end of the engine, a lighter flywheel or torque converter, driveshaft, whatever.

 

[K.O. SWINGER]

I wouldnt worry about it, its not reciprocating weight, its just rotating. Very slightly harder to accelerate, probably impossible to measure, and if it does a better job of removing the harmonics.....? (which is its most important job).
You can probably get that four pounds back on the other end of the engine, a lighter flywheel or torque converter, driveshaft, whatever.

that was my train of thought also it just seemed quite a bit heavier than my stock one

 

[toolmanmike]

I wouldnt worry about it, its not reciprocating weight, its just rotating. Very slightly harder to accelerate, probably impossible to measure, and if it does a better job of removing the harmonics.....? (which is its most important job).
You can probably get that four pounds back on the other end of the engine, a lighter flywheel or torque converter, driveshaft, whatever.

Exactly. It isn't a slinging weight but just a spinning weight. Just like a flywheel. Oh, your engine might rev a millisecond quicker with a lighter balancer on it but who's counting!

 

[yellow rose]

that was my train of thought also it just seemed quite a bit heavier than my stock one

4 pounds on the damper and you’ll have what?? 35 pound of converter or 48-50 pounds of clutch hanging off the other end?

I can tell you I used to spend big money to get my stuff as light as possible and I wasn’t worth it. I was getting wrist pin issues and all kinds of junk.

As far as damper weight is concerned, that 12 pound damper will act like about half that weight or something close to that. That’s because the inertia weight inside the damper “floats” in the silicone gel. It’s not mechanically hooked to anything. So the crank only “sees” the weight of the housing and the hub. Which is about half the total weight, maybe a bit less than half the total weight.

Also, Chrysler has written on this topic quite a bit. Damper weight is critical to controlling harmonics. When they developed the 426 damper they made it bigger and heavier for a reason.

BTW, if you look at how FD develops a certain part number for an application, (you can find this information on the web if you want to read it for yourself) one of he first parameters is how much weight the inertia ring needs to be for all the specifics of the application. And they have to make it fit in the real estate they have. Thats’s why the older FD’s are thicker...they needed the weight.

Damper science is fascinating stuff. So don’t worry about the weight. Just take good notes and check the damper every oil change. You do that buy using a temp gun and measuring the temp of the damper to a bracket or similar very close to the damper. The damper needs to be hotter than that bracket or it’s not functioning. I write down what bracket I’m using to monitor temp on and then I wrote down in my note book why the temp is on the damper so it it is having an issue I can catch it (haven’t had one fail yet but you never know).

 

[Locomotion]

Pioneer 872037 is an SFI balancer/damper very similar to OEM 340.

PM sent.

 

[K.O. SWINGER]

4 pounds on the damper and you’ll have what?? 35 pound of converter or 48-50 pounds of clutch hanging off the other end?

I can tell you I used to spend big money to get my stuff as light as possible and I wasn’t worth it. I was getting wrist pin issues and all kinds of junk.

As far as damper weight is concerned, that 12 pound damper will act like about half that weight or something close to that. That’s because the inertia weight inside the damper “floats” in the silicone gel. It’s not mechanically hooked to anything. So the crank only “sees” the weight of the housing and the hub. Which is about half the total weight, maybe a bit less than half the total weight.

Also, Chrysler has written on this topic quite a bit. Damper weight is critical to controlling harmonics. When they developed the 426 damper they made it bigger and heavier for a reason.

BTW, if you look at how FD develops a certain part number for an application, (you can find this information on the web if you want to read it for yourself) one of he first parameters is how much weight the inertia ring needs to be for all the specifics of the application. And they have to make it fit in the real estate they have. Thats’s why the older FD’s are thicker...they needed the weight.

Damper science is fascinating stuff. So don’t worry about the weight. Just take good notes and check the damper every oil change. You do that buy using a temp gun and measuring the temp of the damper to a bracket or similar very close to the damper. The damper needs to be hotter than that bracket or it’s not functioning. I write down what bracket I’m using to monitor temp on and then I wrote down in my note book why the temp is on the damper so it it is having an issue I can catch it (haven’t had one fail yet but you never know).

yes I believe it said the working weight was 8 lb I didn't understand what that meant but you cleared it up. Thank you for the information excellent response.

 

[K.O. SWINGER]

Pioneer 872037 is an SFI balancer/damper very similar to OEM 340.

PM sent.

I did look at that balancer originally and would have probably made it the one that I bought, but I got a great deal on this and it looks really solid

 

[yellow rose]

yes I believe it said the working weight was 8 lb I didn't understand what that meant but you cleared it up. Thank you for the information excellent response.

Did you find actual data showing it’s effectively 8 pounds? If so, I’d like the link. I can’t remember exactly what that number is. I thought it was about 50% of the total weight was considered rotational. But that was back in 1988 so I may be foggy on that.

And IIRC, that 50% wasn’t set in stone. It was affected by the actual diameter and thickness you can make the damper and what is needed to control the harmonics.

Interestingly enough is that even the stiffness of the crank affects what the torsional vibrations of the crank are. So...if you go from say a stock cast crank to a 4340 non twist forging, even with the same stroke and Bob weight, the resonance frequency will change, and if you are using an elastomer type damper, which has a very narrow range of dampening you have now made that damper at the least less effective.

Like I said, the science behind resonance frequency and all that is very interesting.

 

[33IMP]

I would be more concerned with the speedmaster unit with pulley alignment.

 

[yellow rose]

I would be more concerned with the speedmaster unit with pulley alignment.

Same with the early FD’s. They are thicker. I forget how much though. March has serpentine pulleys for the FD offset. That’s what I’m buying when my junk goes back together.

 

[K.O. SWINGER]

I would be more concerned with the speedmaster unit with pulley alignment.

Yep I was just thinking about that . as I mentioned in the first post my car is in the paint shop but looking at the dampener it seems to be quite a bit thicker.

 

[K.O. SWINGER]

Did you find actual data showing it’s effectively 8 pounds? If so, I’d like the link. I can’t remember exactly what that number is. I thought it was about 50% of the total weight was considered rotational. But that was back in 1988 so I may be foggy on that.

And IIRC, that 50% wasn’t set in stone. It was affected by the actual diameter and thickness you can make the damper and what is needed to control the harmonics.

Interestingly enough is that even the stiffness of the crank affects what the torsional vibrations of the crank are. So...if you go from say a stock cast crank to a 4340 non twist forging, even with the same stroke and Bob weight, the resonance frequency will change, and if you are using an elastomer type damper, which has a very narrow range of dampening you have now made that damper at the least less effective.

Like I said, the science behind resonance frequency and all that is very interesting.

I just went off the jegs catalog numbers for fluid dampener which it seems to be a direct knock off of, with the same static weight of 12.3 lb