Overdrive Pulley


Fubar

Totally ****** Up
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I was thinking about adding a slightly larger pulley to the main crank. I don’t want to down size the supercharger pulley for more boost, plus I think I may be seeing some belt slip at current levels. I thought this might be a good fix with minimal hardware changes. Has anybody tried this, any unintended consequences?
 

paul b

GT Owner
Nov 2, 2006
810
Maybe try mustang forums?
 

Fubar

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I've already got the part. I was just wondering if anyone has done this with the GT motor. Specifically thinking about water pump cavitation?

FYI: The process requires some milling of the trimming indicator.
 

Empty Pockets

ex-GT Owner
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FYI: The process requires some milling of the trimming indicator.

"Timing" indicator?

(Jus' messin' with ya...)
 

Fubar

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Yes, the timing indicator. I didn't alter the trim indicator... that is still working as intended.
 

B.M.F.

GT Owner
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Jan 29, 2009
1,782
Minnesota
I'm doing a 8.120 crank pulley. 1'' larger than stock and i have a 7.375 now and they also make one that is 7.9''...Leave the 6 rib diam stock. Just increase the blower pulley size.
 

Fubar

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Oh that's right, the water pump has a different belt! Doh. What else does the big belt spin, the alt? I also got the 8.120 pulley from ATI. Are you using that on a Whipple car or you pro charger? I was kinda wondering about the calculations on boost. I'll let Fish do the math.
 
Last edited:

ultrasportracing

GT Owner
Aug 31, 2011
490
Perth Western Australia
Just wondering about the bottom end balance,, Is the crank ballanced seperately or is everything ballanced as a complete unit. So does changing the crank pulley upset the engine ballance..
 

Sinovac

GT Owner
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Jul 18, 2006
5,832
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Indy, would you like to answer this question? :)


Just wondering about the bottom end balance,, Is the crank ballanced seperately or is everything ballanced as a complete unit. So does changing the crank pulley upset the engine ballance..
 

2112

Blue/white 06'
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Motor is internally balanced.
 

Fubar

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It's my understanding that the stock crank does not have counter weights but performs remarkably well inspite of that. I'm sure their are some more educated answers available here. For my part, I am changing so many parts connected directly to the crank that I don't think it's possible to predict the results. Luckily John (@ Accufab) has a lot of experience with his motor and has documented results on most of these modifications. The carbon clutch is the only big change that I haven't heard a lot about on this motor. The weight difference is significant enough to have a big influence on the crank. Common sense would lead you to believe that less rotating mass is better but it many have stated that there is nothing common about the logic of engine harmonics.
 

ultrasportracing

GT Owner
Aug 31, 2011
490
Perth Western Australia
AHH every crank has counterweights, if what you mean is that the crank is ballanced seperately, then as long as flywheel ,clutch, etc has a zero ballance then nothing is effected. I would love to get rid of that front pulley, must weight 10/12 kgs(25lbs) Does anyone have any tech info saying the crank is internally ballanced