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Motor choice for an Early Bronco

Dan's EB

Dan's EB

Not so junior
Joined
May 21, 2020
Member Number
994
Messages
127
Loc
Chandler, AZ
So I've got a '74 Bronco that has an old tired motor that I built on a budget back in 2001 when I was an E5 in the Navy. Here we are 20 something years later and the motor is wore out. I have a stock 351 roller motor half rebuilt on an engine stand and a 408 stroker motor that I was building for a '72 Cougar project that's taking up all my garage space. So I have a choice to make. I want to get rid of the Cougar because I need to focus on the Bronco and I really don't care about the Cougar. I can either build the stock 351 roller motor on the engine stand or repurpose the 408 stroker motor that's in the Cougar for the Bronco. My only concern is maybe he 408 is too much for the Bronco and I'll break driveshafts and/or axles.
I'm leaning on the 408 for the Bronco and sell the Cougar with the roller motor as is.
Thoughts..
 
By the way, I have a ZF 5 speed and 4.11 gears so it's not exactly fast, more of a dirt road cruiser now days. My hard core rock crawlin' days with this Bronco are over. It's worth too much money to tear up in the rocks. that's what my side by side is for.
 
Are you going to sell the Bronco? 351.
If not, 408, if you've stopped really off roading it, you can't break anything.
 
welndmn said:
Are you going to sell the Bronco? 351.
If not, 408, if you've stopped really off roading it, you can't break anything.
Click to expand...
I agree with this. I have an injected 5.8 in mine and it’s great. I have the NP435 and it idles through the rocks so much better than the 5.0.
As soon as it shows signs of needing a rebuild I plan to do a roller 408 kit. But I wouldn’t do it for selling a Bronco.
I am a lot more careful wheeling mine now. It’s not retired, but goes on easier runs now.
 
So I put a hundred miles on the ole Bronco today. Drove out to my brothers place. Stayed on the surface streets instead of the freeway since my rear tires are junk, 9 years old and all cracked up junk. I think I hate the detroit locker in the rear, makes the truck (wagon) too squirrely.
 
Blown Hemi is the only proper answer to these questions. Down grade as you see fit. Seems like the 408 would be a great down grade.
 
Tree point five EB (stick with the theme) and a XR80 of your choice.
 
Downgrading the Detroit is odd. You are convinced the tires are trash but blame the locker for bad street manners ,:confused:

Any of the limited slips will be fine. None will fix bad tires
 
If you aren’t wheeling your rig anymore then there’s no reason to put up with the bad street manners of the Detroit. If you occasionally wheel and have the budget then go with a selectable locker.
 
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My 2¢, run the 408. Plenty of guys running 351-based strokers in their Broncos and if you aren't wheeling it very hard or launching it down a drag strip, I wouldn't worry about the 408 causing any breakage.

The only style of limited slip I would ever consider installing is a helical gear design like the Detroit Truetrac. They provide more lock up than most clutch-style limited slips, don't wear out, and don't require special gear oil additives. The factory Ford traclocs don't provide much lock up and they wear out pretty quickly. The clutch rebuild kits are expensive enough that I wouldn't waste money rebuilding one. I know David Freiburger is a fan of the Wavetrac which supposedly still transfers torque to the wheel on the ground when one is in the air unlike a Truetrac or other helical gear designs.
 
A 4 BT might work well for that frame ?
 
I like the idea of the 351 in the EB and save the stroker for something that can better use that engine.

I have an Auburn LS in the 9" in my '73 EB and it does fine for my uses. I won it in a raffle though or I probably would have gone for a True Track. It will power both wheels even if one is in the air, so no real complaints. That said, my EB is more of a weekend cruiser than a rock crawler.:homer:
 
Provience said:
Downgrading the Detroit is odd. You are convinced the tires are trash but blame the locker for bad street manners ,:confused:

Any of the limited slips will be fine. None will fix bad tires
Click to expand...
True the rear tires are bad but this locker has always behaved poorly on the street. The spool I had before the Detroit was at least predictable.
This thing will send you in the other lane when shifting moderately hard.
 
I had a 69 351 with lightning/ cobra efi in my 71, it was a monster and would bark 35s with the c4 shifted, but it took up a bunch of room in the engine bay, with a 2" body lift and a hood scoop, the intake still rubbed the scoop:laughing:
Still was fast with 38s and 4.11s, would peel out but not chirp on shifts anymore

In comparison the 289 with reworked heads and a 4bbl was fun in my 67 with 3spd 3.50s and 31s

Depending on all your other plans for the truck, I'd be considering an explorer 5.0 freshened up, maybe cam heads and tuning to get to some arbitrary hp level 350/375 etc

It seems that with your trans and gearing, the longer stroke might not do you any good over a snappy 302/306

Disregard if the year is 1984 and you're towing your airstream with it
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I think the Detroit is worse because of driver habit and issues with the truck like tire pressure/wear/etc. making it do weird things.

Manual trans and lighter trucks make it worse. Both my fullsize trucks with automatics very occasionally have a ratchet while driving in a straight line which is unexpected. For the most part you wouldn't know it's back there.

Agree that for a wheeling or all around truck as far as limited slips go it's TruTrac all the way. I also think that most people would be happier with that over a full time or selectable but it's not "hardcore" enough. Fact...unless you are 3 wheeling it all the time and pushing the truck to sheetmetal damage a TruTrac is really all you need.

I'd actually vote that it's better then a locker for most situations because it will grip up to the point of tire lift. Unlike a locker which will keep going to the point of the truck doing very bad things. Now if you are in a dedicated wheeling truck and that isn't important or it has all the armor then yeah who gives an F. But for a DD not the case.

For what you are describing about this project spool, Detroit, and all kinds of power don't seem to me useful or necessary.
 
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