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Bronco Engine Swap

mgorzell

New Member
Joined
May 7, 2010
Messages
10
Loc.
San Antonio
I have a 1975 bronco with a 3-speed tranny. I want to swap out the engine with a 302 from a 1991 mustang. What if any problems will I encounter: clutch wont match up, motor mount issues, etc..
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Welcome.
There are a few issues. and lots of solutions. The flywheel is to small you will need a 164 tooth flywheel with a 50 oz balance. You'll either need a flywheel off a 82up truck with a 5.0 or have your current 302 flywheel rebalanced to match the 91 engine. Also pressure plate bolt patterns on the newer flywheels are usually different than your old 302 pressure plate.
Also the stock bronco clutch linkage wont fully bolt up to a 5.0 engine. As the 5.0 doesnt have the boss drilled and tapped like the early blocks were. but there are brackets availible from some of our venders to fix that or some people just drill and tap the block.
Next depends on what front dress you are going to use. stock mustang or stock bronco? If stock mustang then the water pump inlet is on the wrong side and you will have to adapt the lower radiator hose to reach the other side some people have used a piece of exhuast tubing to do this or bought a new radiator with the lower outlet on the other side.
If you go with the stock bronco front dress then your main concern will be bolting the pulley's to the harmonic balancer. Usually you will have to buy a new balaancer to do this again most venders sell a balancer that will work.
Those are the biggest issues there may be a few other's but for the most part nothing else big. Stock bronco motor mounts will work exhuast will bolt up ect.
You might want to check out the links and tech articles as there's a few good write ups on the same swap.
 
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mgorzell

mgorzell

New Member
Joined
May 7, 2010
Messages
10
Loc.
San Antonio
Thanks for the reply!!
The 91 302 has the clutch and bell housing attached, all pulleys, the starter and headders, ect.. I am going to be pulling the intake and carb off the old bronco 302. Will the new clutch bolt up to the older tranny?
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,312
Will the new clutch bolt up to the older tranny?

Lots of potential problems here. Mustang clutch is small, not meant to be used in something as heavy as a Bronco. Mustang had cable actuated clutch. May need to fabricate something to work. Trans may or may not bolt to bellhousing and depth could be different. Just swapping to Bronco bellhousing is not an option because the starter won't work with the smaller flywheel.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Ditto I dont believe the mustang bellhousing will bolt to the bronco tranny. The later trannys have a diffferent bolt pattern and I think the pilot hole is also different. If your going to run a carb on the 91 engine you will need to get a steel distributer gear for the distributer other wise you'll wear out the stock gear quick and may trash the engine.
 
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mgorzell

mgorzell

New Member
Joined
May 7, 2010
Messages
10
Loc.
San Antonio
So I'd prob be better off just using the engine and taking all the rest of that stuff off. This engine has been modified and has been carburated for some time now. I'm kind of torn between just rebuilding the bronco's 302 and calling it a day. I'd hopped to kill two birds with one stone by putting in the mustang 302 because it has a clutch, power stering pump, and is supped up a little. What do you think?
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,312
The mustang motor is a good upgrade. You just need a 50 oz-in flywheel that can accept the Bronco clutch and you'll need a clutch pivot bracket. Then use the Bronco bellhousing and motor mounts. If the motor doesn't have a fuel pimp you'll need to get an electric one. Take a look at the distributor gear and see if it's worn badly. If it is it probably is cast iron and should be swapped for a steel gear.
 
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mgorzell

mgorzell

New Member
Joined
May 7, 2010
Messages
10
Loc.
San Antonio
I wanted to say thank you for your help. I am new to the site and am very impressed with the knowledge and quick feedback I got. I do think I'm going to rebuild my 1975 302 and beef it up. I do trully appreciate all the words of wisdom and am sure to be back in need of more, thanks.
 

dalesbronco

New Member
Joined
Oct 31, 2013
Messages
2
302 efi in 69 bronco

I just purchased a 96 Explorer 4x4 with 5.0 engine. 76000 original miles. Thinking about dropping everything in my 69. Any advice? I have been told it works great. Also i have been told you can use the rear axle assembly that is already set up for disc.
 

rguest3

Contributor
Bronco Guru
Joined
Dec 13, 2012
Messages
3,778
WH has your Flywheel (50oz) and clutch you need. They also have the Bellhousing Bracket for the stock Bronco clutch linkage.
 

w1945

New Member
Joined
May 6, 2013
Messages
12
I am in the process of installing a 1995 Mustang Cobra engine into a 1970 Bronco. The fuel system gave me the most trouble. Tons of dirt in the eyeballs. I have not dropped the 95 engine in but checking the motor mounts the 95 mounts from the front of the motor mount stud to where the bell housing hooks up is 13 7/8 inches. On the 302 which I pulled out the measurement is 12 5/8 inches, so that is not going to work. I am hoping to just swap the 302 mounts onto the 95 engine. O2 sensors will have to be added and wired to the computer. This might help some out there. Most 02 sensors have two white wires, one gray wire and one black wire. One of the white wires goes to + 12v and the other one goes to ground, if you switch them it makes no difference because they are the 02 heater. The gray goes to ground. The black is the signal and the left 02 sensor goes to pin 43 on computer and the right 02 sensor goes to pin 44 on the computer. The wiring at first can drive you nuts but if you stay with it you can figure it out. I wired the thing to where it is incorporated right into the Bronco wiring. I use the 95 Mustang wiring harness.
 

w1945

New Member
Joined
May 6, 2013
Messages
12
If anyone has a problem with the wiring if you will post it here I will try and help. I have the complete wiring prints to the mustang and the bronco.
 

w1945

New Member
Joined
May 6, 2013
Messages
12
Smog eliminator

So I'd prob be better off just using the engine and taking all the rest of that stuff off. This engine has been modified and has been carburated for some time now. I'm kind of torn between just rebuilding the bronco's 302 and calling it a day. I'd hopped to kill two birds with one stone by putting in the mustang 302 because it has a clutch, power stering pump, and is supped up a little. What do you think?
If you want to jerk all of that smog off of the Mustang engine you will need a smog eliminator which is nothing more than a pulley for the belt to run on. Also you will need two fuel pumps, one a low pressure pusher pump and the other a high pressure pump. You will also have to run a feed line and a return line from the fuel tanks. I think Tom's Bronco has all of the instructions for the fuel setup. One thing that gave me a fit was trying to connect the high pressure line to the fuel rail quick disconnect. I finally realized that I could purchase a 3/8 X 1/4 brass barb fitting and then run some 1/4 high pressure hose straight to the quick disconnect on the fuel rail. If you try and run that 5/16 hose to the quick disconnect it will be to loose. Might work but I did not like the idea of being burned alive.
 
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