Do headers for the 4.0 give you more horsepower and better fuel mileage?

[dieselmech_08]

I'm thinking about rebuilding another 4.0 for my truck n i was wonder if i should put headers on it? I already have a cat back system on it with 40 series flows. I was wondering how much more horsepower would i get and would I gain fuel mileage?

 

[Sevensecondsuv]

Any difference in power or mileage will be negligible. It would probably sound better though. I would only put headers on it if you are doing a bunch of internal engine mods (like porting and polishing, upgraded cam, etc) and headers are required to support the additional airflow.

If you want gas mileage out of a ranger, you need to get a 2.3.

 

[racsan]

if anything you'll get worse milage, you will like the sound of the motor and rev it more. lol. i doubt it would help things much, most factory manifolds anymore are pretty well tuned for optimum performance anyways.
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[Yellowsplash]

The 4.0 OHVs exhaust manifolds are log style and are somewhat restrictive. Headers do help the engine breathe some especially since you have the catback system, but dont expect amazing results... As far as milage goes, you wont notice much of a difference.

 

[AllanD]

Headers will improve things regardless of other engine mods.

And by "mods" I'm talking about compression changes, camshafts, porting work etc.

Or even forced induction....

Headers just plain work.

will they improve power? Probably
Will they improve torque? Yes
will this improve mileage? Very likely Yes even if you actually USE the power.

I doubt I'd be getting better than 20mpg in a 4x4 supercab with 4.10's
without the headers.

Catback systems make the truck sound different, but their improvement over
stock systems can be argueable. it depends on WHICH stock system you have

Or should I say: "which CHEAP aftermarket replacement muffler you have"?

Because some of the "replacement" mufflers are MUCH more restrictive than the factory muffler.
Yes, if "lowest bidder" parts screw something up
replacing those parts helps.

Now I could determine if the headers actually "Gain" both power and mileage if I were willing to put 3.55's in my truck, and thus compare my current truck to my brother's 4.0 supercab, but I'm not willing to do that, even in the name of "science"

From past experience 3.55's are "too tall" for best mileage froma 4.0 in a 4x4 supercab.


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