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4.9L I-6 FSB : pros and cons?

5.7K views 15 replies 13 participants last post by  omp  
#1 ·
Greetings,

I've always heard good things about the venerable 300cid I-6. The low end grunt, the dependability.

I have stumbled upon a '90 Bronco XL for sale right down the street with the 4.9L/M5OD combo in it. I was really looking for a 302 or 351 powered Bronco but who says I can't have more than (1) Bronco?

I am curious about all of your experiences, the good and bad, in a 4.9L powered FSB. Commuting, towing, offroad, mileage, etc. This Bronco would essentially stay as a utility vehicle with some functional improvements here and there (3g alt, winch, saginaw swap, ZF5 swap, rear locker, etc) but remain largely stock and be used to possibly pull a John Boat, commute occaisionally, haul parts, fish, hunt, moderate wheeling,etc. So, it won't be built for more extreme conditions. That will be another Bronco.

Any feedback guys and girls?
 
#2 ·
Pros:
Great torque
Slightly better mileage than a v8
Maintenence is usually very simple
Saginaw upgrade is a breeze with the pump being up top
300's last forever of course (mine just rolled 250k)
With stock exhaust, they are pretty quiet with hunting in mind

Con's:
Not at much top end power as a v8, interstates are not very fun
The M5OD is reliable, but a zf-5 would be better

That basically it in my opinion, for what your describing it sounds perfect.
 
#8 ·
Con's:
Not at much top end power as a v8, interstates are not very fun
The M5OD is reliable, but a zf-5 would be better

That basically it in my opinion, for what your describing it sounds perfect.
It wouldn't see but 1 or 2 interstate trips per week and I'm getting older and more patient :)
The M5OD needs the shift forks replaced. The seller drives it around in 2nd gear right now.The first order of business will be a ZF5 swap if we can agree on price.
 
#4 ·
Pros: you get to join a very select, even special if will, group

Cons: (see pros :goodfinge)

They are a great engine. Lot better torque than the 302 and with more main bearings than rods the bottom end never fails and lasts forever. Keep it full of water and oil and a 300 will take care of you until the bronco falls apart around it.
 
#6 ·
I have been wheeling mine for over 15yrs and I can't complain.
The chevs dodges and jeeps I have pulled out of crap have never complained since either.:rofl:
 
#10 ·
I know I can never say enough good things about them. That's why I have two. :)

Just took mine round trip 250 miles at 75mph and it was one finger on the wheel the whole way. May have dropped to 70 going up some of the steeper hills (probably could have kept 75 if I really put my foot in it), but I'm also getting 4 - 6mpg more than the V8s.
 
#11 ·
I have two that get driven a lot. One has an annoying part time miss that has driven me bananas for a few years.
when I heard a brake booster leaking, I thought that was it, it wasn't.
I changed to EGR base plate gasket, new carb, hose clamp on PVC, tie strap on PCV to hold it in oily grommet, changed ignition module etc etc etc
still shows up at odd times as if to announce "hey.....you didn't make me go away......:goodfinge"
 
#15 ·
Get it. You won't regret it. My 92 is a 300(4.9L)M5OD setup and my only issue was, I didn't do the rubber plug mod and let the transmission get nearly dry. Also, it sat in a garage nearly never moving for a few years and the throwout bearing is a little rough. I wouldn't ever consider getting a Bronco with anything else after owning that one. The 300 IS a Truck engine. Built for tractors/trucks and other vehicles that require serious get there reliability. Like others say, it won't do it as fast as other engines but it will get you there. I've never had a problem getting to and staying at 80+mph in mine either.
 
#16 ·
Wish I had one in my BKO, with M50D isnt' that bad, throw some gears on it and its even better than a 302. I just finished a I6 swap into my superduty thats how much I love straight sixes. I've had them in every BMW and import and can't say enough about em. My neighbor has one in his 95 F150 with M50D had 300K on it when I last saw it 5 years ago.