460/gearing

[captn-t]

I am currently assembling a midststates with a 500 hp. 460 with a wide ratio toploader and 9" ford rearend. I am uncertain as to which gear ratio to run. This is just going to be a street car with some expressway driving. I was thinking about a 3.50 but that still gives me 3300 rpm at 75 mph. What's everyone else running? Thanks for the input

[Back in Black]

Richmond overdrive 6 speed, and I am really glad I went with the 3.0 gears.. 1st is almost too low as it is with the Richmond.

at 70 mph in 5th... 2500 rpm... perfect for under 70 on short freeway hops

at 70 in 6th.... 1900 rpm, perfect for long flat straightaways

Any lower and I would HAVE to use 6th on the freeway, every time. I would think with the 4 speed you would want no more than 3.0 gears.. I would want a 2.78 or whatever ?

[Tom Wells]

Ahoy captn-t,

I have a 521, C6 and use a 2.88 Jag diff. It's perfect for my street use and 17" tires.

Your answer of course depends on the state of tune of the engine, intended use for the car, tires used and weight.

For mostly street I'd recommend the 2.75 posi.

If you use 15" tires you'll probably be able to blow them away any time with the 460 in almost any gear. With 17" tires you still can do that, but you'll have to want to!

Regards,

Tom

[Mr.Fixit]

It's a trade off, acceleration or freeway cruising at a reasonable RPM. I have driven from los angeles to chicago and back in my big block chevelle, without overdrive, using 3.73 rear end gears and 26" tires. I was half deaf when I got there and i used plenty of fuel too. Once you get used to having rear gears better than 3.50 than switching to 3.23's or 3.08's make the same car feel so sluggish. I don't know why people want to cruise down the freeway at 1500 or 2000 rpm, the motor so much prefers running closer to 3000 rom for cruising, so long as you have adequate cooling. Cobras are supposed to be racecars, racecars do not cruise at 1800 rpm, they idle at 1800 rpm.

[niles]

Gee I dont get it.
If you want the race car(?) engine turning 3000 rpm, leave it is 2nd or 3rd.

3000 rev on highway is numbing.

With that power a good starting point is a 3.08. You have plenty of power to pull the gear and are near the limits of traction in 2 & 3 anyway. You may give up a tick in absolute performance; but will be much more satisfied with a all around performance.

gn

[Dior55]

OK, I'm pretty well versed in what rear end to run in a 460 Cobra, as I've just done my THIRD changeover!!!. I have an FFR with a TKO and a crate FMS 535 HP 460. I'm running Halibrand 15" wheels on 275 rubber. When I first finished the car, I had 3.08s that came with my donor rear end. I found that the gears were too high for normal street/highway driving. The crate 460 makes absolutely no power under 2000 rpm, so unless I was really reving up and popping the clutch I wasn't getting the blistering take offs I imagined. Also, at highway speeds, I couldn't put the tranny in 5th until I was doing 75 mph, otherwise the engine would just lug as soon as I'd hit a small hill.

I then went completely nuts and installed a 4.10. Just the opposite happened. 1st gear was absolutely useless (shifting when under the red light in the intersection -- I actually started to start from a red light in 2nd!) and at 70 mph I was at around 2700 rpm. Ears ringing if gone for a 30 - 45 highway stint!

I've just installed 3.55s. Perfection.

[niles]

Doir55:
Are you doing 70 mph at about 2100 rpm?
I've run the numbers and a 3.55 is best theortically; however I,m going to try the 3.08 with stroker first.

gn

[Dior55]

Originally posted by niles


Doir55:
Are you doing 70 mph at about 2100 rpm?
I've run the numbers and a 3.55 is best theortically; however I,m going to try the 3.08 with stroker first.

gn

Unfortunately, my speedo cable disintegrated when I went to change the speedo gear for the new ratio. My supplier is backordered so although I've driven the car and am extremely happy with the 3.55's, we'll have to wait to give you the right numbers.

3.08s aren't going to work for you. Especially with a stroker, you'll be lugging the engine on the street. Strokers need to breath, BBs need to spin to make power.

[Dior55]

Got my speedo cable in. With 3.55s, in 5th gear at 60 mph, I'm showing 1900 rpm. This is running 275/50-15 rubber. Also using the 19 (I think) "pink" speedo gear. Don't forget, the TKO-I tranny has a tall overdrive in 5th.

[aumoore]

Here you go play with this and figure out what gears you want.

http://www.smokemup.com/auto_math/mph_range2.php

I would say something from 3.27 to 3.55 gears.

[Dior55]

Hey Aumoore, that's a cool site for calculating ratios! Based on the info I input, it looks like my speedo is pretty accurate.

Niles, it looks like 2100 rpm would be about 70 mph in 5th.

I'm telling you after running almost 1200 miles with 3.08s and another 5500 miles with the 4.10s, the 3.55's are the way to go for general street use on my BB/TKO set up. I can't describe it. The car pulls so nicely, so smoothly, so strong -- the power curve is just sweet. It's like I have a different car!

I guess you could say I'm extremely happy with the 3.55s and HIGHLY recommend this ratio for guys in a similar situation to mine!

[IntimidatorI]

Here is my 2 cents worth. I have a 460 dual carter 600's on a tunnel ram and wild cam. My 9" has 3.25 with a wide ratio toploader. You gotta remember these are light cars, ya my cam doesn't even START to come in until 2000RPM but for my car and 295 rubber which is 26" this is a great setup. I am running down the freeway at about 3000RPM. These cars were not meant to go to ChiTown in from LA. Suck it up - I use ear plugs for long runs. Remember, these biiiiiiig block cars are Harley's on 4 wheels.

My problem is PLUGS. I have the large plug C8A heads and 10.5 compression. With all that carburation I can't seem to get anything colder than Autolite 45's to work for any length of time ON THE STREET. Any suggestions. eric

[niles]

Ref: the plug problem; are they fouling/misfiring?
Check for being too rich; many 2X4 have a too rich problem.
If fouling you need a "hotter" plug for round town/slow driving: not a colder plug.

gn

[Back in Black]

One can have the best of both worlds. My cobra is indeed a touring car with a trunk large enough for 3 good sized suitcases.. and it can cruise at high speeds all day long, while we listen to the stereo.. can hear it at any speed with my NASCAR baffles

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Also, um, I don't see the comparison between a harley and a cobra..

Harley slow

Cobra fast

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[IntimidatorI]

I took a look at your Black Beast which looks very nice - and I want you to take this the right way - but maybe I can understand why you might say that you don't see the comparission between my car and a Harley. My car is built to very original specs and most people that see it or ride in it harken it to the starkness of a Harley - nothing but engine and wheels. My car captures the brutality of the original sceen and feel of having a REAL big FORD engine STUFFED into a REALLY small car. Peaple never forget a ride in my ride. Those comments come from non-owners and Cobra-owners alike. My car does have a senseable side - we just haven't found it yet. PS: It has won car shows and can be driven to the Home Depot to pick up stuff! Want to race?
eric

[Jahred]

I run a TKO and a 3:50 with my 514. Got no complaints. Gearing works out about identical with my 944T. Engine just wont rev as high, but gets there quicker.

[IntimidatorI]

I had a 951 also. Great car, possible the best value for the money on the planet!
eric




I run a TKO and a 3:50 with my 514. Got no complaints. Gearing works out about identical with my 944T. Engine just wont rev as high, but gets there quicker. [/quote]

[427sharpe]

I run 4.11 with an o/d manual trans..gives me 3.28 on the highway.