3.8 to 4.2 using stock Ford components - What is needed - Ford Mustang Forum
 
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post #1 of 6 (permalink) Old 03-03-2011 Thread Starter
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3.8 to 4.2 using stock Ford components - What is needed

I have a 2003 mustang with the 3.8 and I am thinking of making it into a 4.2l. I have looked at a full kit and I see no reason to upgrade to forged parts given that I dont want to rev to the moon or add boost, I am just looking for some good torque gains. What is the easiest way to make my 3.8 into a 4.2? Would it be easier to get a used 4.2l out of a truck and put the top end on or do I need to just replace the crank and pistons from the 4.2. Will I need to upgrade injectors, fuel pump, or anything else to make it work. Appreciate your input.

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post #2 of 6 (permalink) Old 03-03-2011
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swap with the truck engine would be best but im not sure why you would spend the money to do this is like what 20 more hp and a little more tq.
why not spend the money on upgrades for the 3.8?
get a locking diff and if manual get 3.73 gears that will wake that car right up!
a tuner can get you that extra power along with and exhaust and intake.
just weight your options if you want a little extra power look for upgrades for the original motor because after the cost of a 4.2 truck engine and the time to do it it wont be worth it when you could do a few bolt ons to get you there...
i would say yes to a 4.2 if you were going to put forged internals in it and boost it but just wanting a little extra power just look around for bolt ons


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post #3 of 6 (permalink) Old 03-03-2011
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its 20 hp more than youd ever get with all the bolt-ons in the world

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post #4 of 6 (permalink) Old 03-04-2011
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"NO REPLACEMENT FOR DISPLACEMENT" 4.2 out of the same year ford truck is a straight forward swap,swap over your upper and lower intake manifold, pan, flywheel, electrical, etc, bolt in swap, pick- n-pull $180 plus core and tax, for the long block, tear down reseal kit, (head gaskets, oil pan etc,).... SO for aprox 400 bucks what bolt ons can you get for your 3.8 that will give you double digit gains, and you can still do your bolt ons and add moore hp and tq... 4.2 swap.....
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post #5 of 6 (permalink) Old 03-04-2011
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Quote:
Originally Posted by slickbullet5150 View Post
"NO REPLACEMENT FOR DISPLACEMENT" 4.2 out of the same year ford truck is a straight forward swap,swap over your upper and lower intake manifold, pan, flywheel, electrical, etc, bolt in swap, pick- n-pull $180 plus core and tax, for the long block, tear down reseal kit, (head gaskets, oil pan etc,).... SO for aprox 400 bucks what bolt ons can you get for your 3.8 that will give you double digit gains, and you can still do your bolt ons and add moore hp and tq... 4.2 swap.....
Providing it is a good motor. Let the 3.8 vs 4.2 debate begin.......

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post #6 of 6 (permalink) Old 03-04-2011
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I have limited knowlege with the specifics of the 4.2 but.... my 302 to 351 swap (and larger) experience tells me that unless you have a head that flows better and the cam to take advantage of that headflow, then the horsepower level will probably be no different with a motor thats only 20 cubes or so larger, especially if the displacement is the only change.

Yes the torque increase may give you a little more bottom end power, but the rpm range of the motor may drop slightly (assuming heads, cam, intake are the same).

I would say if you have a blown motor, and you can locate a good running 4.2, then go for it, otherwise, I would have to agree that gears and a good 91 (or 93) octane tune are going to make the biggest difference with the least amount of headaches.

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