Stock Pulley as Harmonic Balancer?
06-23-2006, 07:45 PM
#1
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Stock Pulley as Harmonic Balancer? Any opinion on this article, and how it might relate to GM's manufacturing?
"SONIC TECH NOTE SERIES:
SONiC TECH NOTE SERIES:
After market Light weight crankshaft pulleys
Condition:
Flywheel/harmonic dampener and crank bolts coming loose, engine
bearing problems
Never remove the factory crank pulley on any engine to replace it with a
performance pulley or light weight performance pulley. To replace the
factory engineered pulley with something made by a person or company that
does not understand the complete engine design will hurt the
performance/reliability of your engine not help it.
Toyota and many other manufactures such as BMW, Porsche, Mercedes all use
dual mode damper pulley designs in all their engines. I have also received
a similar tech note on crank pulley's from Dinan Engineering (BMW
performance).
The factory stock pulley is designed to absorb both torsion and bending
lateral vibration from the crankshaft. This helps the crankshaft deal with
high vibration in the 400 Hz range after the #1 piston fires. Overall this
has many benefits on the bottom end. It helps the crank deal with high
continuous loads as well as overall bearing life, not to mention overall
engine life. Also the drive-line will have a more pleasing sound with very
little 400Hz vibe's setting up.
See the following jpeg pictures from a Toyota engineering book discussing this!! "
"SONIC TECH NOTE SERIES:
SONiC TECH NOTE SERIES:
After market Light weight crankshaft pulleys
Condition:
Flywheel/harmonic dampener and crank bolts coming loose, engine
bearing problems
Never remove the factory crank pulley on any engine to replace it with a
performance pulley or light weight performance pulley. To replace the
factory engineered pulley with something made by a person or company that
does not understand the complete engine design will hurt the
performance/reliability of your engine not help it.
Toyota and many other manufactures such as BMW, Porsche, Mercedes all use
dual mode damper pulley designs in all their engines. I have also received
a similar tech note on crank pulley's from Dinan Engineering (BMW
performance).
The factory stock pulley is designed to absorb both torsion and bending
lateral vibration from the crankshaft. This helps the crankshaft deal with
high vibration in the 400 Hz range after the #1 piston fires. Overall this
has many benefits on the bottom end. It helps the crank deal with high
continuous loads as well as overall bearing life, not to mention overall
engine life. Also the drive-line will have a more pleasing sound with very
little 400Hz vibe's setting up.
See the following jpeg pictures from a Toyota engineering book discussing this!! "
06-24-2006, 09:28 PM
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Does anyone have any opinions on the long term effects of lightened, underdrive, or otherwise aftermarket crank pulleys on bearing wear, or other negitive impacts to the balance of a rotating assembly etc.. ?
06-24-2006, 11:30 PM
#3
I have only resently replaced the crank pulley with a SLP underdrive unit. Although I have no real history with it I have not read anything bad about them. The SLP unit seems to be actually heavier then the stock cast unit.
That is the extent of my experience with my ls1 but your post did remind me of an experience I had with a Mack truck some 20 years ago. We had a unit purchased used that was retro fitted with a front mount hydraulic pump which did not have the correct from the factory front balancer to be used with a front drive hydraulic system. The first time the engine knocked out the crank bearings we just thought it was because there were more miles then advertised. But when it knocked out the bearing with 6 months is when we discovered the importance of the correct balancer.
That is the extent of my experience with my ls1 but your post did remind me of an experience I had with a Mack truck some 20 years ago. We had a unit purchased used that was retro fitted with a front mount hydraulic pump which did not have the correct from the factory front balancer to be used with a front drive hydraulic system. The first time the engine knocked out the crank bearings we just thought it was because there were more miles then advertised. But when it knocked out the bearing with 6 months is when we discovered the importance of the correct balancer.
06-25-2006, 06:11 PM
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Originally Posted by davered00ss
F-bodies have defenitly had bearrings go bad. Just never heard them atributed to a crank pully. Interesting.
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06-25-2006, 09:55 PM
#9
Without ANY research on this it is impossible to say what is going to happen! No on has ever researched that!
Yes, you are changing the system.
As for the SLP undrive unit. If it is heavier that would be correct. With a smaller radius you would have to increase the weight to get the same resistance to changes in speed. See a dynamics book under the topic of Interial moments or something like that.
Yes, you are changing the system.
As for the SLP undrive unit. If it is heavier that would be correct. With a smaller radius you would have to increase the weight to get the same resistance to changes in speed. See a dynamics book under the topic of Interial moments or something like that.
06-25-2006, 11:54 PM
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Originally Posted by indygoat
This helps the crankshaft deal with
high vibration in the 400 Hz range after the #1 piston fires. "
high vibration in the 400 Hz range after the #1 piston fires. "
I would discount this article strictly on that basis, it is, at the least, poorly written. No doubt the harmonic dampers (I wouldn't call them balancers as they are neutral balanced in our cars, or, supposed to be...) are tuned for specific frequency ranges. I believe ATI advertised that their fluid filled dampers were good to a much higher frequency (hence, RPM) range than the factory rubber elastomer SBC dampers. I made sure to get a fluid filled March underdrive on that basis, and no driveline vibes or any such sort noted. I believe a well-engineered aftermarket SFI-approved piece should work as well or better than the factory peice. I wouldn't worry about it, that's for sure...
07-06-2006, 05:23 PM
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Looks to me like the original text is saying "do not remove your pulley/damper combo and replace it with a lightweight pulley" Not that you should not use a well designed aftermarket damper/pulley arrangement.
07-08-2006, 03:45 AM
#14
I've had a March underdrive pulley on for the last 3 or 4 years and have never been sure if it was acting as a damper also. I went as far as calling the engineering department at March and couldn't get a straight answer. Do any of you guys know? Thanks.
07-09-2006, 12:47 PM
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Originally Posted by bigdsz
I've had a March underdrive pulley on for the last 3 or 4 years and have never been sure if it was acting as a damper also. I went as far as calling the engineering department at March and couldn't get a straight answer. Do any of you guys know? Thanks.
