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Rebuild or Buy new motor
#1
I have a bone stock 1973 Mustang Convertible with a 302 engine and C4 automatic transmission. Took it out the garage last fall to have the body work done. Car started right up after priming the carburetor after sitting for 15 years or so. Sounds good. The car is currently in primer and I am concentrating on the mechanics. Would like to have get the horsepower in the 375 to 400 range along with comparable torque. I understand the is a big jump form the anemic 140 horsepower it came with. Looking for best bang for the buck rebuild 302 or buy a long block and start from there. If anyone has any experience or input that will be appreciated. Originally I was just going to do a top end rebuild with new heads, intake manifold, 4 barrel carburetor,headers, and dual exhaust and a possible camshaft. Does anyone know how much horsepower and torque a stock three speed c4 and the original rear end can handle. Will most likely upgrade the suspension and possibly the brakes. 

Any other suggestion will also be appreciated.

Thank you
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#2
(02-21-2018, 07:43 PM)Cresee Wrote: I have a bone stock 1973 Mustang Convertible with a 302 engine and C4 automatic transmission. Took it out the garage last fall to have the body work done. Car started right up after priming the carburetor after sitting for 15 years or so. Sounds good. The car is currently in primer and I am concentrating on the mechanics. Would like to have get the horsepower in the 375 to 400 range along with comparable torque. I understand the is a big jump form the anemic 140 horsepower it came with. Looking for best bang for the buck rebuild 302 or buy a long block and start from there. If anyone has any experience or input that will be appreciated. Originally I was just going to do a top end rebuild with new heads, intake manifold, 4 barrel carburetor,headers, and dual exhaust and a possible camshaft. Does anyone know how much horsepower and torque a stock three speed c4 and the original rear end can handle. Will most likely upgrade the suspension and possibly the brakes. 

Any other suggestion will also be appreciated.

Thank you
You can meet your HP target with a 302. I have one in my Maverick producing that kind of power. Having said that, I would not personally choose that foundation for a Mustang project given the relatively large engine compartment these cars afford.  If I were seeking a streetable, docile 400 HP engine, I would begin with a 351W. A mild hydraulic roller cam with a good set of aftermarket heads will put you right there and a 351W will produce significantly more torque as well. 

You can retain your C4 and stock 8", provided that you drive it sanely and keep it on the street. I would however, have a good tranny shop upgrade the transmission for more severe duty. 



The c4 can be upgraded to take 400 HP reliably and an 8" rear end will hold up on the street with an automatic. All bets are off if it is drag raced with slicks, however.
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#3
+1 to rotors post
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#4
look into a stroker kit for the 302. that'll run it up to 348 cuin. and make a lot more torque. not sure if a machinist needs to relieve the block so the bigger crank shaft has room to turn. now of course the cyl's go to 30 over so new pistons are needed. don't know if u need new piston rods for the new crank.
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#5
(02-22-2018, 07:39 AM)delawarebill Wrote: look into a stroker kit for the 302. that'll run it up to 348 cuin. and make a lot more torque. not sure if a machinist needs to relieve the block so the bigger crank shaft has room to turn. now of course the cyl's go to 30 over so new pistons are needed. don't know if u need new piston rods for the new crank.

A stroker 302 is an option. The block does require notching for the stroker crank and yes, different rods are required. The wrist pin is located so high in the piston that it breaks into the oil ring land, requiring a ring support. A number of 347 owners report increased oil consumption over that experienced with the 302 even when using the revised ring package. The 302 block is also substantially weaker through the lifter valley and main bearing webbing vs. a 351W. Cap walk is more of an issue with a stroked 302 vs. a 351W as well. 

All things considered, the 351W is a better bang for the buck IMO, if you have the room to accommodate one. It will live longer at 400 HP and like the 302, can be stroked to achieve big block torque numbers.
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#6
runninpony 
In my opinion I would always, always try to rebuild the original engine with some modifications of course!
[+] 1 user Likes NOT A T5's post
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#7
unless its really considered to have been a bad choice to use in the first place, a 302 in a 71-73, a straight 6 in and 65-70........theres something to be said when intact but when the book guides say take half the value off if it has the tiny motor well....................
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#8
(02-23-2018, 04:57 AM)NOT A T5 Wrote: In my opinion I would always, always try to rebuild the original engine with some modifications of course!

I to originally thought the same thing. What suggestions do you have for a rebuild?
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#9
(02-23-2018, 10:32 PM)Cresee Wrote:
(02-23-2018, 04:57 AM)NOT A T5 Wrote: In my opinion I would always, always try to rebuild the original engine with some modifications of course!

I to originally thought the same thing. What suggestions do you have for a rebuild?
As I pointed out earlier, you can achieve your target of 375 HP (400 is a stretch keeping it street friendly) with a 302, but not with a naturally aspirated 1973 302. The 1973 302 has low flowing heads and dished hypereutectic pistons that will make it difficult to build compression.  You can add a better intake, carb and cam and pick up some power, but those heads and low CR are really going to hold you back.


If you insist on keeping it a 302, you can do something similar to my Maverick build. I used a set of early AFR 165 heads, a Weiand Stealth dual plane intake, 600 CFM Summit carb, E303 Ford Racing hydraulic roller cam, + .030" over Speed Pro flat top pistons at zero deck with 58CC chambers and a stock Duraspark II ignition. Timing set at 34 degrees total. 

This combo or something close, will put you between 360-375 HP @ 6,000 RPM with a set headers that will match the larger aftermarket exhaust ports. You will require a higher stall converter, around 3,000 RPM and a set of 3.55 or higher gears to make it responsive in the heavier Mustang. Bear in mind that retaining your stock engine driven fan will cost you some power at higher RPM. You should see 300-325 HP at the rear wheels with a good, high flowing dual exhaust.

You can consider going with either a 331 or 347 stroker which will pump up the torque nicely, at the cost of increased friction losses and higher oil consumption vs. that experienced with the 302.
[+] 1 user Likes rotorr22's post
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#10
Yes I agree that It is also my choice first to make the original motor. I say it is of course your choice and you should always be truthful to what you want to do

Sendt fra min G8341 med Tapatalk

So I'm a proud owner of one Mach 1 73! Regards Lars DK73whistling
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