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#1
09-12-2004, 07:37 PM
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66 gt0 with 389/m20, tripower and summit 2801 cam. Which gear 3.55 or 3.90 would be best??
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#2
09-12-2004, 07:37 PM
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66 gt0 with 389/m20, tripower and summit 2801 cam. Which gear 3.55 or 3.90 would be best??
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#3
09-12-2004, 07:58 PM
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Do you drive it on the highway? I have a 64, same combo and 3.55, has good highway manners. 3.90 is a little steep for the highway. But would be killer for a blvd. brawler.
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#4
09-12-2004, 07:58 PM
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Gear choice depends on what the car will primarily be used for. 3.55 is a good, all around, streetable gear ratio, but 3.90 will get you down the quarter mile quicker. If fuel economy matters, go with the 3.55.
__________________
The 1967 Rustbelt Refugee. Work in progress. Donations accepted. - 467 Cubic Inch EFI Pontiac, Megasquirt II v.3.O ECU, 700R4, 3.55 gears - Best 1/4-mile ET: 12.79 @ 107.36 MPH - Best Fuel Economy: 18.47 MPG ...That's no GTO, that's a Tempest! 
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#5
09-12-2004, 11:39 PM
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My vote would be to make the motor do some work in a quarter and better highway milage.. 3.55's
__________________
'71 Holden HQ Monaro - 3850lbs race weight, 400c/i - 11.4 @ 120 '66 Pontiac GTO - 389, 4 speed street cruiser |
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#6
09-13-2004, 02:59 AM
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Well, it's personal preference to a large degree. A 3.55 and an M20 actually gives you more torque multiplication off the line than a 3.90 and the close ratio, and the wide power band of a Pontiac can handle the rev drops between gears okay. If all you want is a 1/4 mile killer, I would go to the 4.10 and a close ratio tranny, but with the M20 I think 3.55 is ideal. And, it doesn't buzz nearly as bad on the ocassional highway stint. Of course, neither set up is an Interstate cruiser.
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"What could have happened, did." |
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#7
09-13-2004, 03:42 PM
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I think that you should only run the 3.90 if you have a very aggressive cam (RA IV spec or more).
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#8
09-13-2004, 05:24 PM
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If you are running red light to red light, the 3.90 will be more fun, but the rear gear should be selected by all the components that support it. What is the entire drive train?
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#9
09-14-2004, 10:07 AM
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WHEN DOES YOUR CAM FALL OFF?
WHAT WILL YOUR RPM BE AT A DESIRED MPH, TAKING INTO ACCOUNT TIRES AND FINAL TRANNY RATIO? ALL MUST BE CONSIDERED! HOW HGH OF RPM ARE YOU WILLING TO RUN WITH YOUR MOTOR?
__________________
ET 12.504 MPH 107 3940 lbs |
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