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i have a 93 mustang 4cl with a 7.5,,, 3.73 gears in it conventional diff. i think its a code 6. i want to get better gas millage if possible without loosing too much performance. does anyone know of any gear upgrade i can use to help this issue?
 

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well you can get a 3.45, 3.25, 3.08, 2.73. they will all make your rpm drop, but they will trow off your speedo unless you get the right speedo gear. The only problem with any of them is they also take away from torque, so most of the time you will end up using higher throttle angle to try to accel faster. these gears will kill your in town mileage if you dont drive sensibly. Your best bet for better milage is to drive slower, and accelerate slower. keep your foot out of it and you should get about a mile increase. a worn out engine will lower mileage too. it will be less efficient. but dont expect to get much more out of an auto 2.3l.
 

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if you want mileage, put a t5 in it, and raise your compression ratio. Have your head shaved, or put a thin copper head gasket on it. i suggest de shrouding your intake valve too. Remove metal from around your intake valve in the combustion chamber to get it to flow better. i think i get about 32-35, i will check this weekend and let you know.
 

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i have a 93 mustang 4cl with a 7.5,,, 3.73 gears in it conventional diff. i think its a code 6. i want to get better gas millage if possible without loosing too much performance. does anyone know of any gear upgrade i can use to help this issue?
I plan on throwing a 3.08 rear axle in mine from a '86 parts car I have. The trick to saving in town mpg with the taller legs is learning to live and accept lazy acceleration and give it half throttle or less on acceleration.
 

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Discussion Starter #6
cool thanks guys. de shrouding your intake valve? i have never heard of this done? is it hard to do? i plan to eventually shave my head and install some 17lb injectors. let me know cause it would be a great time to do the intake valve when i have everything out.
 

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I will try to get some pictures of the combustion chamber. It really only requires a die grinder, and some carbide cutting bits.
1/4'' Rear Exhaust Air Die Grinder
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the combustion chamber, if you look at it with the valve open you will see that the farther the valve opens the closer the valve head is to the combustion chamber. All you do while de-shrouding is taking this material out of the combustion chamber. you will want the combustion chamber to at least flow in the same direction that the valve moves. I did this and tested it on a flow bench and saw a 10% increase in intake flow. This actually brings the flow geometry to optimal. It will have a 75% exhaust to intake flow rate. This is not a great change in hp, but with a good cam, intake, and exhaust it will make a difference. I personally take all of my heads in and have them shaved .125" or .150". this combined with the reworking of the head will make a very noticeable difference. Good luck!!
 

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Note that if you have the 8 plug setup the valve shroud is not an issue :x i just realized what year your car was. but shaving the head is still a great idea. I converted mine to a 4 plug head with a distributer.
 

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Discussion Starter #9
ok. i see. i planned to to shave the head to .065 to be safe but will .125 or .150 be ok too? this cas will not see a race track but i still want to get a bit more balls out of it and still have it be reliable.
 

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ok. i see. i planned to to shave the head to .065 to be safe but will .125 or .150 be ok too? this cas will not see a race track but i still want to get a bit more balls out of it and still have it be reliable.
I currently have a 1989 ranger, with the 8 plug, and by 1991 that i converted to 4 plug, and they both have .150" shaved off of them. They are reliable as far as i can tell. And my mileage is good. (not in the ranger its 4x4 with 30" mud terrains and it gets 20 mpg :x ;)
 
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