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Hello everyone I have a 1967 mustang with a 302, it’s got a cam, Intake, 4 barrel carb, headers and other engine mods, but every time I stick my foot in it I can get to about 90 (I’m a speed demon) :) and it’s screaming like that’s all it can do, I don’t have a tachometer in the car so I don’t know how many rpms I’m Turning but it seems like a lot, the read end gearing is 2:79 so I’m thinking my transmission is holding it back, it’s a c4 automatic 3 speed, it’s been rebuilt. Can someone tell me the top speed on a c4 automatic. Thank you
 

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65 Fastback 289 4 spd, 65 convertible 5.0L 5 spd. 3.73 8.8
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Hello everyone I have a 1967 mustang with a 302, it’s got a cam, Intake, 4 barrel carb, headers and other engine mods, but every time I stick my foot in it I can get to about 90 (I’m a speed demon) :) and it’s screaming like that’s all it can do, I don’t have a tachometer in the car so I don’t know how many rpms I’m Turning but it seems like a lot, the read end gearing is 2:79 so I’m thinking my transmission is holding it back, it’s a c4 automatic 3 speed, it’s been rebuilt. Can someone tell me the top speed on a c4 automatic. Thank you
AWHTX is correct, I would run the quarter mile at track with 3.50 gears and shift around 90-95 from 2nd to 3rd
 

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The stock specs for the 289 with C4 should be around 117 (theoretical) mph at 4400 rpm. You can research the power/torque curve to get a better set of numbers.
 

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Definitely something holding it back. I've gone quite a bit faster than that with a C4. Probably explains why they didn't last very long for me.
 

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I have a nicely built C4 and I have BURIED the speedo on my 66 years ago. Just saying.
Edit: seems like so many years ago.
2.80 rear and WOW WHAT A NIGHT.
 
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the measured top speed off a GT350 with 3.89 gears was 130mph. in theory with 2.80 gears should at least get you there with a mild 302. but remember it takes more than gearing to get high speeds. you need power to overcome the lack of aerodynamics of the early stangs. in a perfect vacuum your stang should hit about 150 with the 2.80 gears, but you may see closer to 130 if everything is running right.
 

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Rusty,

Missing variable is your rear tire diameter.

But at 5k rpm, a 2.79:1RE, 1.00:1 3rd gear tranny ratio with:

27” rear tire diameter you would run 139mph
26” rear tire you would run 132mph.

our 66 has a 289/c4/3.55 and no issues running 100 mph +.

Are you certain your speedo is reading correctl?
 

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At top speed did the telephone poles look like a picket fence and the lines on the road look like dots?
oh come on, if you are going to post a classic song like this, you have to post the original song by charlie ryan from 1955;


or at least the early cover by johnny bond from 1960;


commander cody didnt do his cover of a cover of a cover until 1974
 

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Stock '68 sedan with the 195 horse 289 would do about 117. (C4 and 2.79 rear axle)
That's about the max speed aerodynamics and horsepower would allow.
 
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I would check and make sure that you're able to put the pedal to the metal. Also when floored take a look and see if the carburetor is wide open. Don't do this while you're driving. LOL
 

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Interesting. Are we trying to kill this person? 'Hey kid, see if you can get it to xxx, brakes be damned.' We have no idea what, if any, improvements, or for that matter things that have even got any attention other than the go fast stuff. A waterbed suspension and shot brakes at 90 will get you dead. Hopefully you will not take anyone with you. It only takes one deer, pothole or other unexpected condition to end in tragedy.
OP: Post where you are and when you go out and do foolish things in a 53YO car so I know to not end up as a victim.
 
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Discussion Starter #16
The bigger question is, do you really want to be running more then 90 mph without some suspension upgrades?
The car has full Coilover suspension
The bigger question is, do you really want to be running more then 90 mph without some suspension upgrades?
The bigger question is, do you really want tot
The bigger question is, do you really want to be running more then 90 mph without some suspension upgrades?
 

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I am thinking it isn't shifting out of second, OR, that rear end has been swapped out. I had stock 66 with C code 289 and C4 and 2.79 gears. I could top it out about 105, engine wasn't screaming, its mild factory build just wouldn't overcome the aerodynamics. I drove a 67 one time with warmed over 289, 4 speed and 4.11 gears and it would barely break 100 and it was winding hard. Couldn't drive across intersection without shifting.
 
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