05-27-2016, 09:41 AM
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#1
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Okinawa986
Join Date: Apr 2016
Location: OKINAWA, JAPAN
Posts: 45
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Underdrive Pulley Questions
Considering Pedro's Underdrive Pulley Kit but read that IMS Bearing Replacement should be done before because of the need to shave down the "boss" or Top Dead Center bolt receiver/holder/whatever (not sure of technical term).
Can someone elaborate on why shaving down the "boss" may make this more difficult?
Can enough of the "hole" be left intact to use it as a TDC guide?
Any other problems experienced as a result of an Underdrive Pulley Kit?
Recommend any other kit over Pedro's and why?
Thanks in advance.
__________________
2000 Boxster S
Zenith Blue
Black Top/Glass Window
Purchased May 2016 w/41.5k Miles
Last edited by DRGETZ; 05-27-2016 at 09:45 AM.
Reason: TMI
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05-27-2016, 10:03 AM
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#2
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Registered User
Join Date: Oct 2008
Location: O.C. CA
Posts: 3,709
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Quote:
Originally Posted by DRGETZ
Considering Pedro's Underdrive Pulley Kit but read that IMS Bearing Replacement should be done before because of the need to shave down the "boss" or Top Dead Center bolt receiver/holder/whatever (not sure of technical term).
Can someone elaborate on why shaving down the "boss" may make this more difficult?
Can enough of the "hole" be left intact to use it as a TDC guide?
Any other problems experienced as a result of an Underdrive Pulley Kit?
Recommend any other kit over Pedro's and why?
Thanks in advance.
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the 4" diameter pulley blocks theTDC locking hole making it difficult to lock drivetrain @ TDC which is critical for successful IMSB retrofit.
__________________
OE engine rebuilt,3.6 litre LN Engineering billet sleeves,triple row IMSB,LN rods. Deep sump oil pan with DT40 oil.
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05-27-2016, 10:21 AM
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#3
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Okinawa986
Join Date: Apr 2016
Location: OKINAWA, JAPAN
Posts: 45
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Thanks for the Reply...
Can't one just install the OEM pulley prior to an IMS Retrofit?
Is there an alternative to using the boss for TDC work and is it a substantially more difficult task?
__________________
2000 Boxster S
Zenith Blue
Black Top/Glass Window
Purchased May 2016 w/41.5k Miles
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05-27-2016, 10:36 AM
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#4
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,280
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Quote:
Originally Posted by DRGETZ
Can't one just install the OEM pulley prior to an IMS Retrofit?
Is there an alternative to using the boss for TDC work and is it a substantially more difficult task?
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Problem isn't the pulley on many models, it is the amount of the boss you need to machine away.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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05-27-2016, 10:51 AM
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#5
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Okinawa986
Join Date: Apr 2016
Location: OKINAWA, JAPAN
Posts: 45
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Can you recommend one requiring less shaving than others?
__________________
2000 Boxster S
Zenith Blue
Black Top/Glass Window
Purchased May 2016 w/41.5k Miles
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05-27-2016, 12:49 PM
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#6
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,280
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Quote:
Originally Posted by DRGETZ
Can you recommend one requiring less shaving than others?
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We do not recommend any of them.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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06-05-2016, 05:10 AM
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#7
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Registered User
Join Date: Jul 2014
Location: Canada
Posts: 487
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Quote:
Originally Posted by DRGETZ
Can't one just install the OEM pulley prior to an IMS Retrofit?
Is there an alternative to using the boss for TDC work and is it a substantially more difficult task?
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Thats what I did. Mantis did the ims and installed one of their pulleys.
__________________
99 Boxster sold
88 944S sold
Xpit Formula Four sold
95 Integra Solo I sold
71 Opel GT sold
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06-05-2016, 06:11 AM
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#8
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,280
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Quote:
Originally Posted by Xpit77
Thats what I did. Mantis did the ims and installed one of their pulleys.
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Depends upon the pulley used, and how much of the boss was machined away to gain clearance. Some people go overboard and do not leave enough to be useful, and some pulleys require more to be removed than others.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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06-07-2016, 07:07 AM
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#9
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Registered User
Join Date: Jul 2014
Location: Canada
Posts: 487
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Quote:
Originally Posted by JFP in PA
Depends upon the pulley used, and how much of the boss was machined away to gain clearance. Some people go overboard and do not leave enough to be useful, and some pulleys require more to be removed than others.
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Mines a DD with a bit of tricks. Not a track or club car . I really dont care about that boss. I`m living on borrowed time with 144000 kms anyway.
__________________
99 Boxster sold
88 944S sold
Xpit Formula Four sold
95 Integra Solo I sold
71 Opel GT sold
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05-27-2016, 11:55 AM
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#10
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Registered User
Join Date: Dec 2015
Posts: 150
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The majority of pulleys I,ve seen don't have the TDC reference hole thru the pulley. Even if you only remove some of the boss and not all you cant lock the crank without a hole in the pulley. I purchased the Mantis pulley last week strictly because it has the TDC hole in it. I haven,t installed it yet as it is still in the mail.
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05-28-2016, 06:35 AM
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#11
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Ben-Auto-Design
Join Date: Oct 2014
Location: French Riviera
Posts: 827
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Ok, so less of a concern for a DYIer.
Thanks! 
__________________
ASE certified Automotive Master Technician.
Porsche Tech in France.
www.benautodesign.fr
Ben-Auto-Design : Performance parts for 9X6 / 9X7
1982 928 S Euro
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05-28-2016, 07:11 AM
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#12
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,280
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Quote:
Originally Posted by Ben006
Ok, so less of a concern for a DYIer.
Thanks! |
Not really, if you decide to do an IMS retrofit after putting one in, you could be either screwed, or forced to spend time taking it back out in order to do the IMS. And if somewhere down the road you need to pull your cam covers to fix an oil leak, or reset your cam timing after repairing your VarioCam system, you better hope you left enough of the boss to allow you to pin the engine at TDC after you also remove the new pulley and reinstall the OEM unit.
These pulley's are not without their merit on the performance side, but they can have very significant time and money consequence's when it comes to future work.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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05-28-2016, 08:04 AM
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#13
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WALDMEISTER
Join Date: Sep 2013
Location: Germany
Posts: 1,344
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Underdrive Pulley might be okay for a track car, but for a DD....meh, not worth the hassle. 
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Original Owner | PORSCHE Boxster 2.7L (MY01) | Seal Gray
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05-29-2016, 10:46 PM
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#14
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Registered User
Join Date: Sep 2013
Location: Chandler, AZ
Posts: 1,796
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I've had the one from Pedro for 2 years now and it works as advertised with NO downsides in day to day use, including the 115 degree Phoenix days.
__________________
03 Carrera
02 Boxster S Guards Red, black interior with matching hardtop
89 Carrera 4
89 944 S2
78 911SC
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05-30-2016, 12:43 AM
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#15
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Registered User
Join Date: Apr 2016
Location: Netherlands
Posts: 57
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A good machines pulley should be fine. I sell underdrives for old Volvo's @ Nordic Car Parts and never had any complaints
I don't know much about the M96 engine yet but usually you don't need to shave anything to install a underdrive pully.
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Current:|Volvo 760 Turbo *White-Rice* '86|Volvo 242 '77|Volvo 360 Cup '86|Volvo S90 '98|Volvo 145 '71|Volvo 745 turbo 86|
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12-19-2016, 10:50 AM
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#16
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Registered User
Join Date: Aug 2016
Location: Illinois
Posts: 26
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Quote:
Originally Posted by Porsche9
I've had the one from Pedro for 2 years now and it works as advertised with NO downsides in day to day use, including the 115 degree Phoenix days.
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Can those of you that installed the underdrive pulley from Pedro, explain/show how you held the pulley to re tighten the bolt? The pictures of his pulley I've seen don't show any holes to use a pulley holding tool.
Thanks!
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05-30-2016, 08:09 AM
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#17
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Ben-Auto-Design
Join Date: Oct 2014
Location: French Riviera
Posts: 827
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on the m96 you do have to shave part of the cylinder 1 TDC boss!
__________________
ASE certified Automotive Master Technician.
Porsche Tech in France.
www.benautodesign.fr
Ben-Auto-Design : Performance parts for 9X6 / 9X7
1982 928 S Euro
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06-04-2016, 02:00 PM
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#18
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Registered User
Join Date: Mar 2015
Location: Katy, TX
Posts: 9
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Benefits of higher performance underdrive pulley
like everyone else, I am always looking for that next performance upgrade for my 1999 986 Boxster: have already done L&N IMS retrofit, FVD performance software, K&N air filter, FabSpeed Sport Headers, Fabspeed MaxFlo Exhaust system, replaced OEM cable throttle body with 1999 996 74mm cable throttle body so I could install 996 IPD Plenum, put Victor Rims and Yokohama tires on it, adding NT Auto rear wing and diffuser, drives great and sounds even better.......... pardon my ignorance, will replacing the OEM underdrive pulley with higher performance system add HP and/or torque, if so, is there consensus on which manufacturer is best?
__________________
1999 Boxster 986,Silver / Black Interior 5speed manual
LN Engineering IMS Retrofit,K&N performance air filter
FVD performance software,Fabspeed Sport Headers, Fabspeed MaxFlo Exhaust,Victor Zehn Rims, Yokohama tires
996 74mm throttle body, 996 IPD Plenum
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06-04-2016, 03:19 PM
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#19
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Registered User
Join Date: Dec 2015
Posts: 150
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An underdrive pulley doesn't create horsepower but it spins the belt driven accessories slower leaving 5_7 hp extra for driving the wheels. It also might lengthen the life of the power steering pump
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06-04-2016, 04:38 PM
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#20
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Artist, 986S tinkerer
Join Date: Aug 2013
Location: Montreal, Canada
Posts: 1,821
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On the track, we are running 4k to redline constantly. The peripherals, especially the power steering pump doesn't like this. I intalled the RSS pulley and shaved off just enough of the boss so that it would clear. Extra HP? Not sure but if I can reduce equipment failures when I'm at the track, it's an easy mod. If you don't track it, don't bother.
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James now has: 2008 987S 6 speed
Crashed: 2010 987.2 pdk in speed yellow! 
Sold to a cool racer chick: 2004 986 S
YouTube channel: the PORSCHE as seen by NewArt
www.youtube.com/channel/UCohdrH2xHTklM1thxk0KKOQ?
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