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Discussion Starter · #1 ·
What's the best all 'round rear gear for a dual-carbureted 331? I'd say 90% street, 10% strip and 10% atuoX. I'm gonna try to keep it at 110% if I can.

I think the 3.73's might be more fun and all, but what about on the freeways?

Thanks gents
 

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I vote with what FFR says... 3.55 for a stock engine... Since you have at least 100 more HP, don't do the 3.55 (or 3.73's) First gear is not useable on WOT starts. I have heads, E-303, 1.6 roller rockers, #24 inj, 65mm tb and 73 mm Mass. Tire size will affect what happens too. I have 275/50-15's that are almost 12" wide and I have spun them shifting to third (yes, it will scare the crap out of you). I like my 3.27's. At highway speeds they're just right.


Mike
FFR 2335 and 3917 SB
 

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I had 3.73s in my old 5.0 Mustang and I didn't care for it on the steet. First gear was too fast, RPMs were fairly excessive on the highway, and its harder to hook up all else being equal.

I won't be going more than 3.55 on my Cobra if that...
 

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And I also hope I get to use mine 110 percent also. But I digress.

I have decided to compromise. I expect to be about 500 HP in the final form. Give that, total weight, and a desire to keep the highway revs more reasonable (I want to do a lot of road trips with my wife) I'm going with 3.27 gears.

Hank J.
 

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Discussion Starter · #6 ·
Originally posted by Mcathcart:
I vote with what FFR says... 3.55 for a stock engine... Since you have at least 100 more HP, don't do the 3.55 (or 3.73's) First gear is not useable on WOT starts. I have heads, E-303, 1.6 roller rockers, #24 inj, 65mm tb and 73 mm Mass. Tire size will affect what happens too. I have 275/50-15's that are almost 12" wide and I have spun them shifting to third (yes, it will scare the crap out of you). I like my 3.27's. At highway speeds they're just right.


Mike
FFR 2335 and 3917 SB
Mike,

I see your point; everything is inter-related (tire size, engine size, HP/Torque curve, gear set and all).

I'd like to run 18" Bullitt or Cobra R's - but to be honest, I haven't as yet even considered tire sizes. I wanted to get the rear end done next, prior to installing the 331 in the stang – but to be honest, installing a new engine just to remove it again to reinstall it in a few months down the road sounds stupid-er and stupid-er, and the garage is starting to take on the appearance of a parts bin. I could have sworn I had a plan here somewhere. WTF?

Joe
 

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Because I went the victor Jr setup on my motor (higher hp and less torque) I decided to take a shot at the 3:73 gears. I can't tell you how it's working yet, I am still building.
 

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Discussion Starter · #8 ·
With my set-up, I think I'm leaning toward the 3.27 gear set from what I've read so far.

It should be easier to get a lighter car up to speed, and therefore require less torque - a higher gear might work better. Just my thoughts on it.
 

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Like the assembly manual reads, 3.55 wakes up the stock build. Having pointed that out I found the FFR guys knew exactly what they were talking about. It would be pointless to use lower gears.

My stock engine would run out of air on the straight at 5200 rpms. With the 305X heads and Cobra intake it will rev up to 6100 on the straight in 4th just as it's time brake for turn one.

My 99 Cobra aluminum pumpkin came with 3.27s so I left them in and used the gear change money to port the heads and intake. You guys that didn't run the open track at the Las Vegas Nationals really missed a lot of fun driving what you built in a safe environment.

I vote for 3.55s and 3.27s if you have a little extra power. I have driven 1225 25K miles and about 5K of that is on a road course trying to learn how to use WOT.

Roger
 

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Originally posted by 93stang:
With my set-up, I think I'm leaning toward the 3.27 gear set from what I've read so far.

If you have the money..... I maintain that a 327 rear with a t-5 with the .8 OD is the perfect setup for our cars...

IF you want to do track events, you are going to run out of 4th gear at about 128 with the 355. even sooner with the 3.73. Then you shift in to that rediculus .67 od and get below your HP curve.

A 327 will get you close to 150... which is more than you need to do in the first place.. :D :D

and the 327 first gear is NOT totally wasted.

Just my .02$ worth.

earl
 

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Maybe I'm in a minority. I wouldn't even consider the 3.27s. For a small block, you may find 4th and 5th nearly useless. Acceleration in 1,2 and 3 will be pretty good, but it'll really slow down and lose it's responsiveness in 4th and 5th.

If you plan to run 18" wheels :eek: , that'll slow the car even more. I have 17" wheels in my car and run the 3.73s. My motor is a bored 351W. Unless you plan to cruise the highway at 100+ mph, it's not a problem. I have great acceleration out of the hole (I can get traction with very troubles most of the time), and the car is very, very responsive through all gears. On the highway, I'm turning about 2500 rpm or so at a nice cruising pace. I think it's perfect. As the 3.55s are quite close, I think you'll find them quite similar.

Steve
 

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Here's some experience from someone also running the F-28 setup...

I have 17" wheels with 275-40's in the rear and I have the 3:55 gears. I can't comment on CobraEarl's assessment of the triple digit factor, as like you most of my driving will be on the street where that range is "not very practical". First gear is a little short, but I never found it to be a real issue. The overal responsiveness more than makes up for any shortcomings! Highway cruising is extremely comfortable, however, to have passing power it is usually necessary to use 4th gear, as 5th is strickly an overdrive at "normal" highway speeds. My engine is a standard bore 5.0 with "B" cam and 1.7 roller rockers which increase it's lift to about the same specs as the "F" cam. I also have aluminum Edelbrock 6037 heads with the combo. I've never had the combo on a dyno, but have been told it should be good for about 325 - 350hp.

I personally would not run anything lower like 327, unless alot of your driving was going to be on the circle track. For all around street performance you can't go wrong with the 3:55's! Even though a 427 stroker will eventually be replacing the present setup, I still plan to use the 3:55's...

my $.02
Brian
 

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Originally posted by CobraEarl:
[/qb]
I maintain that a 327 rear with a t-5 with the .8 OD is the perfect setup for our cars...


earl [/QB][/QUOTE]


That's what I have and I like it just fine. My car is primarily street driven with the usual bolt-on stuff like heads, headers, TB, etc. Nothing fancy. I'm at about 285 HP and I still think for me, 3.27 is just right. The lower gears are usable and the 0.8 overdrive puts me in the low 2,000 RPM range on the interstate. It's the best of both worlds.

Rick Williams
 

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I've had 3:73's in my car for 3 years now and I'm going to spool back to to a 3:27. I might add also that I'm runnning a T-5Z with a 2.95 first gear which helped, but I think the 3:27 ratio will be much more suited for the street. I've got a 351W, with appox. 375-400HP. You can find 3;27 gears all day on E-Bay. Cheap too! Paid $18.41 for mine. Just my $.02 Mike
:cool:
 

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Initially, I had the 327's but have since moved up to the 373's. Most modified, high HP, carbureted motors require higher rpm's to run clean and to stay in their power curve. I'm running a 351W dynoed at 437hp at the crank. My motor feels much better over 3000 rpm than under it. Highway cruising at 3200-3300 rpm equates to 100 mph; just where I prefer to be both for rpm and for mph. Running 3000 rpm on the street in second equates to about 35 mph.

For however much the first gear is too short with the 373's compared to the 355's of 327's, you gain in ALL the other gears. As for track use, no two tracks are alike so no one set of gears will be best for all tracks.

All the best,
Bob
 

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HEY 93STANG!!!!!!! Where you at in Cleveland?
 

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My vote is for 3:55's. I have put gears in atleast 11 FFR's. IMO 3:55's is the best all around gear for me from mild to wild (225 -550 horse). First is a little short but 2nd and 3rd more than make up for it.
Jeff Hamilton
 

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Originally posted by B+L FFR 1686:
I have the 3:55 gears. I can't comment on CobraEarl's assessment of the triple digit factor,

I personally would not run anything lower like 327, unless alot of your driving was going to be on the circle track. For all around street performance you can't go wrong with the 3:55's! Even though a 427 stroker will eventually be replacing the present setup, I still plan to use the 3:55's...

my $.02
Brian
If you have no intention of opentracking the car... a 355 is probably the best all around street rear gear. I totally agree.

BUT, if you intend to do open track envents, you need to look at your usable rpm range vs speeds at different ratios and rpms.

One HUGE advantage to 327s for the BUDGET BUILDER is they are stock in a lot of automatic convertible Mustangs..


My car has the 3.55 gears and I run out of gear at open track envents below 130. ;) ;)

earl

[ January 22, 2004, 07:43 PM: Message edited by: CobraEarl ]
 

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My donor has 3.08s in it and I was thinking of using it. Most driving would be rural as there is hardly any cities for 150 miles. (western nebraska). I guess from what I am reading here that you guys dont agree?
 
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