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Fla GTA 1
Newbie
Joined: 20 Oct 2008
Posts: 5
Location: Bonita Springs, Florida |
Rear Axle Question
I have a 67 Fairlane GT. The car had a three speed manual trans from the factory. Some one changed the trans to a C-4 and I believe left the original 2:90 or 3:00 gears in it.
I have two questions. Would this rear axle be an 8" and also, I was looking to go to a 3:80 posi set up. The car has a 289 with an Edelbrock 1460 4 bbl carb and 289 performer intake manifold. The engine also has a mild cam, and headers, the specs I have no idea of. I think that the horsepower is not put to it's potential with this small of a gears.
I don't do a lot of highway driving but I do some. Might I be better off with a 3:55?
Thanks,
Ted
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Mon May 04, 2009 9:52 am |
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GerryProctor
Senior Member
Joined: 10 Mar 2006
Posts: 660
Location: San Antonio, Tx |
Should be an 8" axle. A 3.55 gear will help a lot, but it will not turn it into a tire-shredding beast. You need torque, which the 289 doesn't have a lot of. I would not go higher than a 3.55 unless the engine can buzz to 6k rpm and make power up there.
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Mon May 04, 2009 6:11 pm |
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Fla GTA 1
Newbie
Joined: 20 Oct 2008
Posts: 5
Location: Bonita Springs, Florida |
quote:
Originally posted by GerryProctor:
Should be an 8" axle. A 3.55 gear will help a lot, but it will not turn it into a tire-shredding beast. You need torque, which the 289 doesn't have a lot of. I would not go higher than a 3.55 unless the engine can buzz to 6k rpm and make power up there.
Hi Gary,
Thanks for your reply. As I said, I really don't know what the former owner of this car did engine wise. since The person that I bought it from purchased the car already done.
What would be the best way for me to see if it will make HP in the 6 grand range? Run it through the gears manually to see how it reacts at 6 grand?
Thanks,
Ted
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Tue May 05, 2009 6:23 am |
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maroon63
Member
Joined: 06 Jan 2009
Posts: 63
Location: southern ohio |
Years ago when I was running around on the street,I found 3.25-3.50 gears to be a good set for a mild combo.I ran my best ET with my 67 Must.351C auto and a mild 5500 rpm cam with the 3.50 gears.The old Fairlane had the same engine at one time with a 4 speed and my best ET was with 3.25 gears.Keep in mind this was on standard street tires.It did make them driveable on the highway going to cruise nights and car shows.
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Tue May 05, 2009 6:55 am |
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bulletpruf
Senior Member
Joined: 14 May 2006
Posts: 304
Location: Woodbridge, VA |
quote:
Originally posted by Fla GTA 1:
quote:
Originally posted by GerryProctor:
Should be an 8" axle. A 3.55 gear will help a lot, but it will not turn it into a tire-shredding beast. You need torque, which the 289 doesn't have a lot of. I would not go higher than a 3.55 unless the engine can buzz to 6k rpm and make power up there.
Hi Gary,
Thanks for your reply. As I said, I really don't know what the former owner of this car did engine wise. since The person that I bought it from purchased the car already done.
What would be the best way for me to see if it will make HP in the 6 grand range? Run it through the gears manually to see how it reacts at 6 grand?
Thanks,
Ted
Ted -
If you knew a bit more about your engine internals, that would help. However, kind of tough to do that without tearing it down. Bottom line, however, is that a mild 289 is not going to make a bunch of power, either down low or at high rpms. 3.50 gears might help, but I wouldn't recommend going any higher. If you want the car to move out smartly, look into swapping in a 351. 390's are also cheap, but you'll end up having to buy more parts for that swap.
As for your current ratio, just jack the car up, mark the driveshaft with a piece of chalk, same with the tire. Count the number of driveshaft revolutions for each tire revolution and that will give you the gear ratio - 2.8 turns of the driveshaft for a single turn of the tire equals a 2.80 gear.
Good luck,
Scott
_________________
67 Fairlane 500 Hardtop, 796 hp 514, C4
66 Fairlane GT Convt, built 390, Toploader www.bulletpruf.9f.com
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Mon Jun 15, 2009 7:35 am |
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