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4.0 swap ahead


Joined
Nov 6, 2019
Messages
21
City
knoxville TN
Vehicle Year
1990
Transmission
Manual
I have read and read and read about installing a 4.0 in my 1990 B2 fm146 2.9.

What is something that you told your self that you would do differently if you had to do it again !

Thank you
 
You have just about the most ideal vehicles possible to do that swap... the only thing you're going to run into is the auto trans wiring if you use your 5 speed and I'm assuming you will. Easy to overcome that issue. Start swapping!
 
If you can, I recommend replacing the oil pan gasket(with a hefty amount of ultra black silicone), valve cover gaskets, exhaust manifold gaskets, spark plugs, water pump, rear main seal, etc. while you have the engine out. It's much easier than doing it while it's in the truck.

If you are going with the manual trans, make sure you get a 4.0 flywheel, clutch and starter. The FM146 should be fine behind the 4.0 for a while, provided you don't abuse it. You may want to look into getting an M5OD
 
Just wondering why. I cannot turn my 33s very well past 60 going up a grade even at 5k rpms. I live in Knoxville Tennessee and it is very hilly.

Because he’s in the 2.9l mafia.
 
So there no reasoning other than he likes the motor ? I guess someone has to love it. I mean it could be a good turbo motor I guess ? Lol
 
So there no reasoning other than he likes the motor ? I guess someone has to love it. I mean it could be a good turbo motor I guess ? Lol

Id regear if it were me. A 4.0 still isnt gonna be happy under those conditions.

I am a proud 2.9 flag waver, but every 4.0 ive ever driven didnt really feel gutsy enough to justify ripping out a running 2.9 for.
 
How much different would a carbed 302 be ? Vs a 4.0.
Stock for stock? Not much better.

But a 302 can be built to be damn more potent then a 4.0.

Or get a 94+ roller 302 and convert it. They had 40 hp and 55ftlbs on a OHV 4.0.
 
The only thing I can say about it...is a question....is

why was it not in there the day it was built ???

For driving in your conditions ...which I know well and have driven a 2.9 and my 4.0 broncos in the same place...the difference between a 4.0 and a 2.9 is the difference between a 460 and a 351.

Huge casm in how the engines actually work under load. On paper it looks close...in reality it's huge. Probably would not have swapped a v8 into my truck if it was equipped with a 4.0 and a manual the day I got it. Instead of the 2.9 and a-frail-ld fail o matic.trans.

The 2.9 5 speed is great in a b2....4.0 is fawesome.
 

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