3400 Crank Pulley???

[97cutlas$upreme]

mine went in with out a problem.. fits both the 3100/3400 from ffp

[Joseph Upson]

I think this is a good time to look at GM and the penny pinching times of today. I can't imagine it would be cheaper to make a 3 piece dampened pulley than it is to make a solid cast pulley, that being said, since GM is still installing dampened pulleys on the V6 there must be a good reason for the added cost. Vibration forces can be very powerful and I imagine one of the greatest reasons a 4 cylinder is apparently less in need of a dampner is because there are two fewer pulses generated into the crank than on the six cylinder.

Perhaps it would be a magnified need under the circumstances of detonation when some of the pulses generated into the crank by the piston and rod assembly are out of sync. I'd be afraid to risk it even for a 15 hp gain.

[geoffinbc]

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.

Makes no difference man. Tortional vibration has nothing to do with balance or engine configuration. It has to do with simple forces and the fact that metal stretches and acts like a spring when it does.

All you guys have to do is some simple searches on the internet to learn the facts about it. Quit dismissing this as a myth or and un needed part. If it was then it would not be used on every single engine built for the last 100 years. I've done my reasearch and have been to school for millwright and have done vibration analysis, studies on metal fatigue so I understand what is going on in pretty good depth. Some people here should at least scratch the surface on this issue and quit buying shitty parts off the internet. It is not acceptable to sacrafice reliability for horsepower, any engine builder will tell you that. You can't win if you can't finish

[AaronGTR]

Vibration forces can be very powerful and I imagine one of the greatest reasons a 4 cylinder is apparently less in need of a dampner is because there are two fewer pulses generated into the crank than on the six cylinder.

You have that backwards. 4 cyl's need dampers even more than 6's. Many 4's even have internal balance shafts as well because they run rougher. Of course, many tuners also make balance shaft removal kits because the shafts are heavy and often are rotating in the oil pan and cost a lot of HP. Are they right or are they wrong for removing them? Who knows. All I know is several magazines have tested them for significant power gains as well as long term dependability and even rally racing them and have had no ill effects.

The basic rule though (with few exceptions) is the more cylinders in an engine the less vibration it will have. It's because there are more pistons firing for every revolution of the crank shaft so it maintains a more constant speed compared to the slowing down and speeding up of the crank when there are less cylinders firing and there is more time between each power stroke.

[prophiseer]

The basic rule though (with few exceptions) is the more cylinders in an engine the less vibration it will have. It's because there are more pistons firing for every revolution of the crank shaft so it maintains a more constant speed compared to the slowing down and speeding up of the crank when there are less cylinders firing and there is more time between each power stroke.

Almost dead on the mark. The more cylinder's the less primary imbalance, secondary is a whole 'nother story (which is why most if not all v8, v10, v12 have harmonic balancers). 4 cylinders are more prone to primary imbalance which is why most have balance shafts (or some very odd engineering, i.e Q4). A few TDOHC v6's have balance shafts also, but those are usually over-enginered motors (volkswagons, BMW, etc.). But anyways, v12's are just about in perfect balance, throughout the powerband.

Correct me if I'm wrong, though, but I thought the OHV 60* were internally crank balanced; there's so little rubber on the crank pulleys, I never really thought it was dampneing much.

[MMGT1]

I thought it was mainly interior balanced as well??

[sharkey]

88+ 60 degree v6 motors are internaly balanced, 87 and prior are externaly balanced. even the externaly balanced motors have a 0 balanced damper, they only have a weight on the flywheel.

[MMGT1]

^^^^^^^^^^that's good info to know^^^^^^^^^^^

[zofo61]

Got the RSM pulley...had it for a year and a half.....boosted....no dampner.......all good.......no history lesson.....done

[MMGT1]

Ha Ha Ha Ha Ha Ha Ha^^^^^^^^^^^^^^^;

[barrok69]

Got the RSM pulley...had it for a year and a half.....boosted....no dampner.......all good.......no history lesson.....done

I'm not boosted... but ditto the rest.

[SappySE107]

Never heard of a crank breaking on an 85+ 60V6 from either power or no harmonic balancer. Theory and real world don't always get along.

[boarderbob]

I don't mean to jump back into this, but I've been doing quite a bit of research so I thought I'd throw in some of my thoughts.

Firstly, the harmonic balancer, or more appropriately the harmonic damper, doesn't necessarily have to do with the balancing of the engine's rotation. As "betterthanyou" has been saying it's main design is to absorb torsional vibration.

Secondly, torsional vibration does not deal with the balancing of the engine (kind of redundant I know), more importantly it's not a result of engine balancing. It deals with the cylinders firing and the forces that act upon the crankshaft as well as the deflection that occurs during this process.

This is all directly in line with what "betterthanyou" has been saying, though I can't speak as to how precisely necessary this part is. Just my thoughts.

[prophiseer]

to the best of my understanding, it seems to me that the harmonic balancer is actually used to reduce the amount of vibration caused from the drivetrain. The engine itself is balanced through the counterweights on th crankshaft, sometimes also by means of one or two balance shafts also, but once the actual transmission is engaged to the crankshaft, you're dealing with more rotating parts being slapped on the end of that assembly. Flywheels, clutches, and torque converters are usually balanced in some way or form; but those balance properties will change once the motor and transmission are turning in unison. The Harmonic balancer is meant to reduce, if not eliminate, most of these vibrations to the crankshaft.

[Joseph Upson]

My bad, the more cylinders involved the closer the length of the crank comes to being equally stressed via twisting forces so it would make sense for the 4 cylinder to require dampening more. The only thing the anti balancer option has going for it IMP is the increasingly stronger GM parts, GM particularly indicated that the 3500 and up crank's pin diameter increase was to help reduce engine noise/vibration.

I don't recall my 84 Fiero 2.5L having a harmonic balancer or balance shafts when I rebuilt it, maybe that contributed to the stinkyness of the crank that would eventually try to come out of the block and ride in the front seat with you after too many trips above 5000 rpm.