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is it possible to carb a 4.0?


mikhail

mikhail

Well-Known Member
Joined
Aug 20, 2007
Messages
155
Age
36
City
Houston
Vehicle Year
1988
Transmission
Manual
Ive been wondering if its possible to put a carb on a 4.0. Its the same block as a 2.8 right? so is it possible to swap over the intake manifold and carb and run it rich? this would make it way easier to swap it into a BII since you wont need a ecu or harness right?
 
Let's get this straight... you WANT to break your engine?

Sure it's possible to put a carb on a 4.0L. Remove engine. Go to junkyard. Get a GM 250 I-6. Install. Now you have a carbureted 4.0L (well, 4.1L). It weighs twice as much as your 4.0L and has half the peak power. Big improvement, eh?

And before you start talking about interchanging parts, figure out how you change the bore AND stroke and use the same block to do so. Not even SBCs keep the same block between models.

Intentionally running rich will kill your power and plug up the exhaust.
 
MAKG, I think he meant run the carb rich compared to the 2.8. Thinking along the lines of 'more displacement, more fuel.'

But yeah, you can't do it. If you want the 4.0, just take your time and figure out the wiring.
 
I think he meant run right.

I think the 4.0 weighs about the same as a Chevy 250. I've pulled both and they have about the same feel. Doesn't sound scientific, but compared to a International Harvest 345 or a Ford 460 they are light and those are 650# motors. I'd put the 4.0 at 400# and the 250-6 about 450#. A smallblock Ford is about 450ish as well.
 
mikhail said:
Ive been wondering if its possible to put a carb on a 4.0. Its the same block as a 2.8 right? so is it possible to swap over the intake manifold and carb and run it rich? this would make it way easier to swap it into a BII since you wont need a ecu or harness right?
Click to expand...

Very little will swap between a 2.8 and 4.0. They mixed some things around between the 2.8/2.9 (timing gears to a timing chain so the cam spins different directions so the intake/exhaust port locations changed) that would put a bad wrinkle in carberating a 2.9, then they made the block bigger for the increased bore and stroke of the 4.0 so even less is the same. Then to top it off the 4.0 has a distributerless ignition you would have still have to figure a way around if you had a custom intake made.

Personally I would go for a 4.3 before I would go for a 250, but that is just me.:D
 
Will said:
I think he meant run right.

I think the 4.0 weighs about the same as a Chevy 250.
Click to expand...

I've never pulled the 4.0L, but that Chevy 250 is a HEAVY SOB. I don't see how it can possibly be the same weight as a V6. It's almost twice as long and it's all cast iron, except for the pistons. Even the intake manifold (such as it is) is cast iron. The crankshaft alone is a heavy lift and it takes a big guy (or two not-so-big guys) to move the bare block. It's certainly FAR heavier than a 2.9L, and the bare block is significantly heavier than the bare block on an SBC. It's also a very tall engine, though not all that wide.

I'm not suggesting that a 250 I-6 is a good thing to put in his truck (though I must admit I do like the really, really low powerband for the 67-72 version, for that application -- though to be usable, it would require regearing).
 
Last edited:
didnt know the block was that much different, sorry guess that was a really stupid question then? I was just thinking about it, cause there was a guy on one forum i saw that said he might be able to put a 2.9 distributor in a 4.0... and if i do a motor swap i might wanna go carb i hear the wiring isnt too hard for EFI but im not sure, its my DD cant be down for too long. anyways im still going to wait for the 2.9 to crack a head or something, it only has 160k on it and i hear they go over 200k often so it might be a while. thanks for the responses, i just heard the block was the same and was wondering
 
There is a set of simple truths that people only come to understand
after they live with an EFI engine.

1) most of the myths about how troublesome they are are either exageration or lies.
2)That the simplicity and reliability of a carb is an outright lie.
3)That the best carb engine falls considerably short of the
average EFI engine of the same displacement...

Converting your early Ranger/Bronco2 to EFI is not all that hard
all you need is a good organ donor or a good junkyard.

there are plenty of people who will talk you through it all in detail...

AD
 
I don't know, it'd look pretty cool if you just mounted individual downdraft carbs to the existing lower plenum!


Dave
 
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