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Mach73

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'73 Mach 1
So, i have a stock 85 HO 302 w/ AOD. it is going into a 73 mach1 (keeping origninal on shelf). The mach is F code, C4 trans (thought was fmx but not) and has 2.79 rear gears.

My main priority is putting that engine and trans into the car to increase hp/drivability. When it goes in i will be adding a e303 cam, (probably) ported e7 heads, and a dual plane intake yet to be determined, and a edelbrok 1406 (E choke) 4 bbl carb. Are those rear gears going to kill me? id like to make nice hp up to 5500 max, not a strip car but not a dog at the light. looking at AFR 165 heads but thats likely to be after the install

Budget is low so also what should i do before i begin, dont wanna have to rip nething out (cam) thats a pain once its in there.

 
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thanks for reply and for the heads link. can i go 3.5 rear in 8" rear end? and will this kill my MPG (all in all i have to get moving first heh) what do u think about the cam?? is it gonna be capable of getting me to 350hp? i would like to atleast double the hp to 280 at a minimum. Thanks

 
If you're considering an 8" rear, maybe you should look at an 8.8 conversion. Much stronger than the 8" and you can find them pretty easily. That is a bit of cam for an automatic. I would consider the 3.73 gears. It should be fine with your overdrive..

 
did some research and i can put in 3.73 or 3.55 in an 8" still kind of afraid of the 3.73...

as far as changing the rear to an 8.8... seems to cost asmuch as putting the engine in... and at that point why not opt for the 9"???

also, Will i be able to move that car if i put the engine in before changing rear gears?(however i decide to do it)

and what do u mean its quite a bit of cam for an auto?? ive heard they were fairly mild but im sure theres something i dont understand here, thanks

 
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Mach73,

Cazsper has a good point on the rear end. Not many option for gears on the Ford 8 inch. A stock unit should be able to handle up to 350 HP. If look on line, a well built 8 inch can handle more. You will find mixed opinions! If you decide to go with the 8 inch, go look for websites that support Pinto racing. They use the Ford 8 inch in their race cars.

What would one need to do to convert a Ford 8.8 to a 1971-73 mustang?

mustang7173

 
The AOD has the same gear ratios as the FMX, with the exception of having the extra overdrive ratio. My car came from the factory with a 351C-2V, FMX, and 3.00:1 rear gears in a 9-inch - and I just swapped in an AOD and punched out the engine to some healthy numbers around 400HP (according to CompCams CamQuest utility).

According to a chart someone posted a few weeks ago regarding rear gears, tire size, RPMs, etc., the AOD's .65:1 OD ratio will have a car with 3.00:1 rear gears spinning 28" diameter wheels at 1800-ish RPM at 60 mph. (I've slept since I last saw the table [Alabama] Don provided, so the numbers might be slightly different). Regardless, it seems to me that off-the-line acceleration would be no worse than a standard H-Code Mach 1... which as I remember correctly, was not all THAT bad.

Even so, adding horsepower (and torque) will only improve acceleration, and I believe would also lessen the impact of 'lugging down' at cruising speeds (65+) when hitting the hills. This also maximizes fuel economy having the lower rear gear ratio and the overdrive capability.

That's still all 'theory' as far as I'm concerned because I haven't had the opportunity to test my set-up yet since the car's not ready for the road.

Just out of curiosity, do you have the stock '85 AOD shifter & bezel? If so, can you take a picture for me? I'm interested to see what it looks like and if it's worth trying to find one for better fitment into my center console.

 
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I ran a 3.40 gear in an 8" with a stout 302 and an FMX and it was damn near perfect. I disagreee about the 8" strength, I suspect it is good to over 400 RWHP which is a bunch at the flywheel.

Axles are same as a 9", bearings are the same size and when have you ever seen a broken ring gear?

I do not like the 5.0 over the 302, but that is because of the crank design changes. Make sure to use the 50 oz balance flexplate with that 5.0 or you will have to pull it back out.

 
I ran a 3.40 gear in an 8" with a stout 302 and an FMX and it was damn near perfect. I disagreee about the 8" strength, I suspect it is good to over 400 RWHP which is a bunch at the flywheel.

Axles are same as a 9", bearings are the same size and when have you ever seen a broken ring gear?

I do not like the 5.0 over the 302, but that is because of the crank design changes. Make sure to use the 50 oz balance flexplate with that 5.0 or you will have to pull it back out.
Click to expand...
+1

 
I'm actually a big fan of the 8.8. I ran one in my '95 GT. Very strong and take less power to turn them than the 9". You can also find then all over as well as parts. I ran a stroked and supercharged 393w (mild cam) and made over 550 RWHP. More than most put to their 9".

Not to mention you can take advantage of the modern disk brakes, torque arms, etc.

Just something to think about.

 
@Mister4x4 i dont have either, sorry man. Thanks for the replies, i think im gonna go ahead with the engine and change the rear

 
You might want to make sure you have a higher stall torque converter as well. Otherwise, you might have a dog at the line.

At least one guy here has a daily driver with 2200 RPM stall and I think a 3.25 gear. He is pretty happy with those settings. But if you want more kick, you get the idea.

 

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