Performance Gain
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Instructor
Joined: Jun 2005
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From: Ringgold Georgia
Performance Gain
I have an 84 which has been converted to a carb and upgraded to a 383. The 700r4 is built with a 2500 stall. I am running consistant 8.70's in the 1/8 mile. I am upgrading to the a-mod 17 inch wheels and plan a ring and pinion change. First, what gear is in it? Second with the move to 17 inch wheels should I go to a 3.73? This is eventually a purpose built hot rod for strip, auto cross and maybe road course duty. It is however still a street car. How much of a time improvement could I expect? It presently runs 8.70's, 1.9 to 2.0 60 foot times and roughly 81 to 82 MPH.
Team Owner
Joined: Dec 2000
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From: SE NY
Cruise-In II Veteran
I think 3.45s are the usually recommended upgrade with an A4 but that is with an EFI setup, so not sure with your carb.
Your goals are really somewhat at cross purposes as a good strip car won't be a good auto cross car. However you can compromise by keeping stock suspension parts overall with an upgrade to the ES poly graphite sway bar bushings. This won't hurt hook at the strip but will improve cornering. Also you can change alignment between street/strip/track.
Going to 17" wheels around will help auto-X with increased cornering stability but slow 1/4 mile times a little due to increased rolling resistance. Bumping the gears should more than offset the increase in wheel diameter. You might want to keep the 16" wheels for drag racing as the taller sidewall combined with a soft tire will aid hookup.
Your goals are really somewhat at cross purposes as a good strip car won't be a good auto cross car. However you can compromise by keeping stock suspension parts overall with an upgrade to the ES poly graphite sway bar bushings. This won't hurt hook at the strip but will improve cornering. Also you can change alignment between street/strip/track.
Going to 17" wheels around will help auto-X with increased cornering stability but slow 1/4 mile times a little due to increased rolling resistance. Bumping the gears should more than offset the increase in wheel diameter. You might want to keep the 16" wheels for drag racing as the taller sidewall combined with a soft tire will aid hookup.
Race Director
Joined: Feb 2004
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If my memory is correct, the base gear in an auto for 84 is 2.59. 3.07 would be the performance axle ratio. I normally do not recommend a 3.73 on the 84-91's. But with the carb, yours may respond well. I think 3.55 would be a safer choice though. This is especially true if overall drivabilty is important.3.73 (to me) suck on the way to the supermarket. Sure feel good when the foot is in it though. 
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Instructor
Joined: Jun 2005
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From: Ringgold Georgia
As with all applications there is a compromise. I want this car to run good at the strip but also handle. I have the energy suspension kit waiting in the garage. I will do ball joints and tie rods at the same time. I bought the lowering kit as well. I am putting on the A-Mod wheels because they look hot, offer better braking options in the future and 11.5 inches of rubber looks wicked. This is my third car option so it sees limited use because my truck is my daily driver and we cant do without a truck. It appears there are only two gear options for the dana 33 which is what mine is , I believe, 3:40 or 3:73. With the wheel upgrade My thinking is 3:40 may be offset not enough and 3:73 may be like a 3:40 with 16 inch wheels.
Pro
Joined: Jul 2002
Posts: 725
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From: copperas cove, texas
I had the same setup as you have and went to the 3.73 and was real happy with that...I was RPM limited to 6500rpm and it just worked out great. With my 17" wheels I was at 2350rpm at 70 MPH in overdrive. Your rearend shoud be a dana 36 with 2.59 gearing..good luck with either choice
BTW: I found that there are two different carriers, one is a 2 series(2.59)and the other is a 3 series. You have to get the correct gears for the series of carrier so its important that you identify your current gearset. I don;t know if this is exclusive to the 84 model but it did create problems for me when I had mine done.
BTW: I found that there are two different carriers, one is a 2 series(2.59)and the other is a 3 series. You have to get the correct gears for the series of carrier so its important that you identify your current gearset. I don;t know if this is exclusive to the 84 model but it did create problems for me when I had mine done.
Last edited by 427t-top; Aug 8, 2005 at 04:02 PM.
Race Director
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
I have to ask: Why would not a really deep gear...like a 4.11...be desireable for a drag car? Would it not be a case of the more torque multiplication the better??
Do the A4's run out of rpm at the top end or what? (I wouldn't think so....)
Larry
code5coupe
Do the A4's run out of rpm at the top end or what? (I wouldn't think so....)
Larry
code5coupe
Race Director
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The (good) problem with a 700 is the deep 1st gear ratio. Something like 3.08 1st gear. A 4.11 almost make for too much gear in most cases. Opinional, but every time we tried it on an auto tpi car, it was not worth it for us. On a carbed car, I do not know.
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Drifting
Joined: Feb 2004
Posts: 1,277
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From: Santa Maria CA
the base gear option was only a 3.07 and the performance axle ratio was 3.31's which only about 400 vettes in 84 where ever made with that ratio.
i went from 3.07 to a 3.54 and saw a nice improvement. much better launch and probobly dropped .3 tenths at best....with the gears and M/T drag radials i'd probobly drop .4-5 tenths total.
if i could change gears out again i'd go deeper like a 3.73 at most. my crossfire has a higher rpm range than a stock/mild TPI car so i can get away with a little more gear than some can. with a carb'd 383 you probobly can hit 6000 depending on your setup so i'd say go 3.73's and get some drag radials/slicks if you don't use em' already.
i went from 3.07 to a 3.54 and saw a nice improvement. much better launch and probobly dropped .3 tenths at best....with the gears and M/T drag radials i'd probobly drop .4-5 tenths total.
if i could change gears out again i'd go deeper like a 3.73 at most. my crossfire has a higher rpm range than a stock/mild TPI car so i can get away with a little more gear than some can. with a carb'd 383 you probobly can hit 6000 depending on your setup so i'd say go 3.73's and get some drag radials/slicks if you don't use em' already.
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Instructor
Joined: Jun 2005
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From: Ringgold Georgia
I am running a com cams xe 274 with Dart pro 1's 200cc intake and 64 cc chambers, flat top 383 with a holley dual plane and Edelbrock 750 carb. I have a set of long tubes and duals (Modified Corsa system) a XE 284 cam and an Edelbrock torker 2 intake waiting on the bench. I have decided that I need to get my drivetrain right before going with more engine HP.