3400 Crank Pulley???

[boarderbob]

Hey everybody, the name is Bob. I've got an issue with a recently purchased 3400 Lightweight Crank Pulley. The pulley was produced by RSM Racing (I know, a questionable decision) and purchased through PFYC.com. I'm just trying to give you some background on the pulley itself.

I took the pulley to a local mechanic to have it installed. After some time of it being with the shop I got a call saying that it didn't fit and that it required a harmonic balancer. They went as far to say that they called the manufacturer to confirm that it wouldn't fit.

So I called RSM Racing to see what sort of answers I could get. They told me that it was properly balanced for my application (2001 Pontiac Grand Am GT). They said that it would fit and that it did not require a harmonic balancer. I emailed them pictures to confirm this.

Thus I come to you. I need to know who is right. The shop has charged me half labor for taking off the stock pulley and attempting to fit this on (which I wonder about). I've bought the pulley and it's past time for any returns. I will follow with a couple of images and some rough dimensions.

Dimensions:

• Overall Diameter: 5 15/16 in.
• Shaft Diameter: 1 1/4 in.
• Belt Track: 1 1/8 in.

There are some pictures here and here as well.

I hope that you can help me. I'm new to the forums here, so I apologize for the length of the post and if I've done anything wrong. Thank you for the help.[/list]

[Guest]

Yep, should slide right on. I know others have used that pulley without any hitches.

A harmonic balancer is not required, but is a good idea, unfortunatly, there are NO aftermarket under drive pulleys for the OHV FWD 660, that incorporate a harmonic balancer.

If you're that worried about it, put the stock balancer/pulley back on and sell the underdrive pulley, possibly to me.

[AaronGTR]

FYI the RSM pulley isn't underdrive, it's stock diameter and just light weight. The FFP is underdrive.


I have the RSM and mine fit just fine. I have had zero problems with it so far. Yourslooks like the same as mine did from what I can tell in the pics. Like Raven said, a harmonic balancer is not "required", it's just recommended for longevity of the engine internals. There are actually very few aftermarket crank pulleys that have harmonic balancers or "dampers" as they're sometimes called. Most are like the RSM one.

If you're curious, the purpose of the harmonic balancer is to "dampen" certain vibrations from the crank shaft to keep them from transmitting to other parts of the engine. These can be more or less at different rpm, and can be better or worse depending on the design of the engine. Four cylinders tend to be "rougher" and need the damper more. Conversly, six cylinder and even more so eight cylinders are "smoother" and need them less. It has to do with having more pistons firing per crank revolution so you get less of the speeding up and slowing down between cylinder firings.

I personally didn't think I needed a balancer. I have a heavier than stock cam shaft and also a blower added to the belt drive and both of those can help dampen the pulses. I also intend to rebuild the internals at some point so...

Anyway, unless RSM sent you a pulley for a different engine, I think the shop is incompetent or trying to pull one on you.

[Manitcor]

no your engine has no need for a harmonic balancer (an offset weight on the pulley) as the 60v6 engine is internally balanced. The stock pulley for 60v6 engines features a harmonic dampener (a ring of a rubber material ment to absorb vibrations in the crank to reduce deflection).

There is much contrversy on if an internally balanced engine actually requires a dampner. Im of the opnion that if you intend of going for a large amount of power you should have a dampner of some kind or have your crank, rods and pistons blueprinted and balanced to remove all imprefections and elimanate any deflection.

If you are only going to midly modify your car then you can likely get away without a dampner though some will argue that it will affect engine longevity.

Myself right now I am running a CNC Alunimum underdrive pulley without a dampner and have for close to 100,000 miles now. I am working on a set of mods that will greatly increase my power output at which time I plan to replace the stock dampner and pulley as tests have shown in high power high revving applications crank deflection can be particularly bad.

[boarderbob]

I have the RSM and mine fit just fine.

Did you notice anything with it? I'm hoping that it lighten things up a bit, not much mind you but every little bit helps.

I do plan on reworking the internals, so I'm not terribly concerned a harmonic balancer at the moment. I suppose I'll look into down the road though. Thanks for the help everyone.

[geoffinbc]

No engine should ever be run without a damper. It is extremly destructive.

Here is a quote from Dennis Wells of wells racing engines. This quote comes from my Engine Masters Magazine. It is an performance engine builders magazine. Smokey Yunick himself has a 10 page artice just on oiling.

Q: How important do you consider crankshaft dampers, and why?

A: "Crankshaft tortional vibration causes crankshaft and flexplate failure, loosened bolts, brooken timing chains, and erratic valvetrain and ignition problems. We tested our USAC Silver Crown car on the wheel dyno. We removed and ATI lightweight damper, installed a small aluminum hub, and made five consecutive runs. We saw no horsepower gains. What we discovered when removing the aluminum hub was that the tortional vibration, in only five runs, was so great that the hub was no longer a press fit. It slid off by hand! How much more proof could you want?"

Everybody needs to learn one thing. Harmonic dampers have NOTING AT ALL IN ANY WAY to do with the balance of the crank. Yes some have offset weights for external balanced motors. But the job of the tortional balancer is to absorb tortional vibration not vibration caused by balance issues. This one part is your only defence against tortional vibrations. So if you all want to go out and maybe see a couple horsepower from a small pulley and be able to tell people you have a light crank pulley or some ricer shit like that, be my guest. But if you want to see years of trouble free service then keep the stock balancer or see if you can talk ATI into making one.

Or if you sweet talk CNC guy into it im sure he can come up with a design. It is a very simple part but it does a very important job.

[boarderbob]

Okay, well with the newfound information I have. I will be looking into getting a dampner for the aftermarket crank pulley. I'm apologize I didn't do my homework beforehand. This is definitely a learning experience and I appreciate all the help.

[SappySE107]

I have discussed it with marc but we are not sure what rubber, thickness, adhesive to use for an UD pulley with a dampener. Given the track record of all these pulleys being used with it...do you really think its worth messing with for the handful of people that would only buy one with the dampener? I dunno but I don't know anyone that has had a problem with theirs. Yes I know what it does and why its important, but the firing order DOES make a difference here.

[geoffinbc]

Buy an ATI damper, maybe a worn out used one and push it apart.

They use an inner hub that fits the crank and then the outer hub sits on what is basically 2 big o-rings between the inner and outer ring. The inner hubs face is the full diameter and has the timing marks on it. This way the outer ring can walk and your timing refrence is not screwed. Take a look you'll see what I mean.

[AaronGTR]

Whatever man. If they don't work why do so many companies make them and so many people use them without problems then? I don't see how that harmonic damper is supposed to have any effect on the valve train either since the timing chain is hooked directly to the crank behind the crank pulley. Any vibrations would hit that chain before they get to the damper. I don't see how these torsional vibrations could be that bad either, but as soon as I start breaking stuff I'll be sure to let you know. I still have my original pulley so maybe I'll dyno 'em both and see what I find (as to wether or not there's really enough gain to make it worth it)

[torq455]

i've had the UD pulley from FFP on my car for two years now and it's great! noticed more topend--yeah, "slid" on with a 3 lbs hammer and a 2x4 block of wood. Have taken it off and on 3 times now and still just as tight. and are we building a daily driver that will last for 200,000 miles, or a performance vehicle in hopes of lasting 50,000? If mine lasts for 50K, that will have well over 5 years of hard service. if things last that long, that would be great for me.

[xonelith]

I'm a little confused, so I apologize for my ignorance.

I have the FFP UD installed and running problem free for 50 000km's. I'm not sure what this dampner you refer to is. I compared the stock vs aftermarket, and I don't see any additional pieces on the stock one. Unless you are referring to the reluctor plate (which I incorporated into the FFP pulley).

Can someone clarify what this is all about? I don't want to have something installed that will kill my motor (considering I'm shifting at 6800 rpm at WOT).

As a sidenote, I didn't notice a difference after installing the pulley, but I haven't taken it off, cuz I'm lazy. Since I saw no adverse affects, I kept it on.

Thanks!

[geoffinbc]

Look back at the stock one. There is a cast iron center and then a rubber ring and another cast ring with the pulley groves on the outside. The outside ring attached to the rubber is what absorbs tortional vibration...

Alot of people are quick to dismiss vibration as not important or non destructive. But if they ever took a course or two in vibration analysis or engineering they would wake up quick. You people can do whatever you want. But when all the winning engine builders (even the shitty ones) build all their engine with dampers on them I would say its for a good reason. They are not doing it for their health.

[MMGT1]

Tim, you think this may be your false KR??? Don't Know if your replacement had the "damper" or not???

[DarkKnight]

But when all the winning engine builders (even the shitty ones) build all their engine with dampers on them I would say its for a good reason. They are not doing it for their health.

They also aren't building 60*V6's. I think it's fair to say that certain engines have less problems with torsional vibrations (such as the 60*V6) than other engines (such as 90*V6). That engine builder could be refering to any engine.