89 5.8 swap into a 91 bronco

[eddie bauer]

You've all probably heard this question a bunch of times but I'll ask it anyways. I have a 1991 eddie bauer with a 5.0 and a mazda 5 speed. It's got about 130,000 or 230,000. I'm not sure how many times the odometer has been rolled. The old 302 is getting tired, is a little low on oil pressure, and is starting to have some valvetrain clatter so I figured it's about time for an overhaul. I have 2 more complete parts rigs, an 87 with a 5.0, and an 89 with a 5.8 both are automatics. I figured I have 2 options. Option 1, I could overhaul the 87 5.0 and put that in my 91 to minimize downtime since I have to drive it everyday. Option 2, I could overhaul the 89 5.8 and install that in my 91, I'd have more power and not a lot more invested in the swap than just a 5.0 overhaul. I am certain that I'd have to get a different flywheel, and a computer for a 5.8 with a 5 speed, if there is such a thing. They're both about the same vintage and use the speed density system, so wiring and sensors should be about the same. I would really like the 5.8 just because it has more power, and I am like every other red blooded gear head and beleive in the old motto "there's no replacement for dispalcement." But if it is going to be a huge hassel and not worth it in the end then I'll go with the 5.0. I have a big shop and I am a mechanic so that is not really an issue. I'm just asking for some advice. Thank you for your time.

 

[Shadow_D]

First to the Zone!

Next... PLEASE update your signature line with all of your truck info to make it easier for everyone to help you when you have other questions. Doing this will make for less typing and wait time for answers for you.

If you put the 351 in using the old 302 computer it shouldn't be a problem, I think it will read is as a great running 302.

Next I'm not sure the 351 would be worth the effort. The HP gains are not huge...

1991 5.0 (302 ci) 185 hp @ 3800 rpm 270 ft/lb @ 2400 rpm (this is your stock motor)

1987 5.0 (302 ci) 185 hp @ 3800 rpm 270 ft/lb @ 2400 rpm

1989 5.8W (351 ci) 210 hp @ 3800 rpm 315 ft/lb @ 2800 rpm

As you can see, you will only gain 25 HP and 45 ft/lb of torque

That to me isn't enough to justify the bigger swap. I have a 90 with a 351W and only get 7 - 10 MPG and that is with a K & N FIPK Gen2 air cleaner.

If it was me I'd do the 302 overhaul with less down time.

 

[BLADE262US]

Cant use the 302 computer the speed density stystem is preprogrammed for volume of air 351 has larger bore therefore more air coming in engine will run lean it will run just not good . I put a 91 351 in my 89 that had a 302 my opinion on that is the 351 is a better option I was way happier with it . Now even though my swap was close in yrs I still had to repin the harness . On mine I had to switch the temp wire and the oil pressure with 2 others that I dont remember now best bet is get a wiring diagram for both and trace it out I have the ford factory prints so was lucky with mine . The connectors have a red divider in the end of them pull it out and there is a catch there for removing the pins to move them around . Id do one at a time and write everything down and pics before you start . It can be done though . /emoticons/[email protected] 2x" width="20" height="20" />

 

[eddie bauer]

Yea I am still leaning toward the 351 swap since I have everything I need. I think I have more time than I thought b/c ther old girl runs excellent best running 302 I've ever owned and I installed a manual oil pressure guage just to check b/c the electronic ones are known to go bad. I have 60 lbs cold @ idle and about 20 lbs hot @ idle so I think shes's in better shape than I thought. Yea repinning a harness isn't that bad of a deal, It just takes awhile I've done it on an old ranger truck I had that I swapped transmissions into, but anywayz thanks for the info.

 

[madmax]

the computer can be reprogrammed for a larger displacement, and the 351 will usually outlive the 302, id bet on you having 130k on it, problem is your mazda trans will be hard pressed to handle the extra torque of the 351, im sure theirs a reason why they put the bigger 4 speeds behind the 351's

 

[eddie bauer]

Yea I was curious if the mazda trans would hold up. I've already broke one just street driving so they're not very tough. Especially if I build the 351 like I was planning on doing. Is there a 5spd trans that will bolt in that will take it? I know they used 5spds in heavy f-350s with 351s my uncle has one. But I'm not sure about it fitting in a bronc. I love the manual trans and I would have to have a 5spd for the overdrive to try and get as much gas milage as possible. I know that was a stupid comment after just talking about hot rodding a 351, lol. But I put alot of miles on this truck. I think I am gonna just run the 302 till it dies. I have more time than I thought. The oil pressure issue was a bad sensor. I would still really like to do this swap tho. So maybe I can gather the parts around and do it sometime in the future when some of my other projects are completed.

 

[Redneck86]

I would go with the 351 no doubt. My 86 has a 351 4bbl and its out run any 302 ive come across, 170k and still runnin strong. Honestly i think a 302 is too small for a Bronco, youll be alot happier with the 351. As for the transmission, if you got 5-speed from an F250/F350 i bet it would also swap in pretty easy.