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Changing gear ratios

 
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Vol
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PostPosted: Thu Aug 29, 2002 2:30 am    Post subject: Changing gear ratios Reply with quote

I am in the process of building a '63 Ford Fairlane 2 door hard top. It will have a 289 with a 600cfm Holley and a four speed toploader. I have 2.45, 2.75 and 3.00 gears for the rear end. My intent for the car is just for crusing. I know the 2.45 will give the lower rpm but will it be to sluggish on start ups and up hill grades. I am searching for past experience. What should I install? My e-mail address is volmoore@msn.com. I will also monitor this site as often as possible. Thanks for help!!!!!!!!!!
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1979 Chevrolet Camaro

PostPosted: Thu Aug 29, 2002 9:56 am    Post subject: Reply with quote

The 3.00 gear should be very liveable on the street, around town and on the highway. I think the 2.45 gears will be great for the highway but will not provide you with the acceleration you'll want.
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MisRed
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PostPosted: Sun Sep 08, 2002 1:13 am    Post subject: Reply with quote

I only wish I had tall gears like that to choose from.

4.11's and 3.90's are the only options in an RX-7 and the torque monger Buick motor typically doesn't like anything in that range. 3.07's would do me nice. Might be installing a Corvette rear soon.

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'87 Mazda RX-7 w/ '87 Buick Grand National Drivetrain
12.3 @ 122.26 MPH

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PostPosted: Sun Sep 08, 2002 8:44 pm    Post subject: Reply with quote

MisRed ... is that with a stock GN motor or is it built?
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MisRed
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PostPosted: Sun Sep 08, 2002 10:01 pm    Post subject: Reply with quote

The long block is completely stock 3.8 '87 GN motor. The only additions are bigger injectors to support the HP, upgraded turbo and that's about it. Based on 3150# race weight, we figure it's making about 414hp right now. Not bad but plenty left in this 3.8. This particular motor was out of a salvage car and the history is unknown. The same combination took my 3800# Buick to 11.92 @ 112mph. That was even with a stock turbo.

I am currently building a 4.1 girdled motor that you will be able to consider 'built'. Roller cam, heads, 259c.i., big turbo. This motor should make ~550hp reliably and propel the mazda to over 130mph in the quarter. Just need to get the car safe and fix the issue with the 4.11 gears.
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jeep_406
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PostPosted: Tue Sep 17, 2002 10:49 pm    Post subject: MisRed's RX7 with 3.8 Turbo Reply with quote

That's a ton of mile an hour. what rpm are you going through the eyes at?
If you can get it to hook. . .it'll run in the 10s.
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MisRed
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PostPosted: Wed Nov 13, 2002 6:46 pm    Post subject: Reply with quote

Sorry for the late response. RPM's through the traps are 4500..

It's got some severe traction issues that need to be addressed with better/bigger tires and a taller rear end gear.

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'87 Mazda RX-7 w/ '87 Buick Grand National Drivetrain
12.3 @ 122.26 MPH

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jeep_406
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PostPosted: Thu Nov 14, 2002 3:29 am    Post subject: RX 7 with 3.8 Turbo Reply with quote

Hi Misred,
Was that 4500 in overdrive or 3rd gear?
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MisRed
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PostPosted: Thu Nov 14, 2002 7:21 am    Post subject: Reply with quote

4500rpms, 4th gear with the converter locked... That's a .67 ratio assuming the converter isn't slipping when locked.
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'87 Mazda RX-7 w/ '87 Buick Grand National Drivetrain
12.3 @ 122.26 MPH

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