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Discussion Starter · #1 ·
Can we get a discussion going on what exactly a 4.2L buildup is?

I'm under the impression that fundamentally it's swapping the 4.2L crankshaft out of an F150 for the stock 3.8L Crankshaft.

I'm also under the impression that the blocks (3.8L and 4.2L) are the same, as are all the accessories, heads, intakes, etc.

Is the fuel delivery mechanism of the stock 3.8 sufficient, or do you need an upgraded fuel pump, bigger injectors? Do you need the 4.2L fuel rail?

What is the impact on the computer? Is the 3.8 computer the same as the 4.2? Do you need a chip, or is it advised?

Do the connecting rods and pistons need to also be swapped for any reason?
 

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For your car the accessories and heads are the same the upper intake wont fit under the stock hood but the lower is the same. Fuel delivery system is the same. The Piston and Rod lengths are different. So when doing a crank swap with a 4.2 in a 3.8 block you will need the proper length rods and pistons for proper deck clearances and the rear main journals are a different size they are smaller and need different bearings. No real impact on the computer but you would want a chip to take full advantages of the swap.

Corey
 

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like corey said. the blocks are the same, but the stroke on the crankshaft is longer so you get .4 more liters. a chip and a dynotune are the best way to make the computer know that youre getting those couple hp and ton of tq. the 99+s and 4.2s use the same returnless fuel system and same 21# injectors. so youre good to go there.

i think i read that the lower intake off an F150 is just slightly different.... its got an extra hole for a vacuum hose or something like that, that you just plug. so basically its the same. the upper is too tall to use and wont fit, so you just reuse your stock one. the heads are the same.

the best way to go about it is to buy a the 4.2 block though. the reason is you will spend $~300 for the crank and pistons and rods (minimum) and then pay someone $1200 to install it all for you. you can get a shop to drop an engine in for $300 if you have it and pay $800 for the shortblock.

pre99s need a lot of work to use a 4.2 with the splitport package. they need the block (see above paragraph because its cheaper, but stock will work), they need a modified fuel rail, larger injectors, prefered larger fuel pump, chip, new TB, new CAI, and some other things. you have to do the split port swap on it while doing the 4.2 swap.

pre99s can also take a 4.2L block and put their stock heads and intakes on it. it will work just fine. you just dont get the 40hp you gain from the split port setup. that way you dont have to mess w/ the fuel rail (still advise new injectors) or the hours upon hours of dyno tuning. just need 1-2hours to tell it about the new stroke.
 

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If my motor needs replacing anytime soon I will use a 4.2 shortblock and use my P&P heads, cam nand P&P intakes. Should make nice torque numbers.


Corey
 

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Discussion Starter · #5 ·
So a nice setup would be to get a 4.2block, something like SSM's powerpak or whatever EE is going to come out with (heads and cam) P&P the 4.2 lower intake, put a 3.8 split port upper and a dyno tune. Are we looking at 250rwhp here?
 

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easily. the stock 4.2 is about 205bhp and then the power pack is about 60rwhp. so about 170+60 = 230. plus all the other bolt-ons and the chip for advanced timing and such. 250rwhp isnt hard to get. the torque is what would be amazing. the stock 4.2s are like 250tq or something like that instead of 225. plus the power pack and such. be up there w/ a new GT
 

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Discussion Starter · #7 ·
somewhat off topic, but if a 3.8L is a 232cu in what is a 4.2L?
 

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look at my above post. youre a pre99 right? you need fuel mods, the crank, the rods, the pistons, the computer reflashed/reporgrammed. new flywheel if its externally balanced. i forget which years are internal and which are externally balanced.
 

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fox body 1983 is a carb model, custom 4 bbl manifold avail from Morana racing and it is a pre '94 no pump change but inline electric fuel pump with a regulator would work
 

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I think that if I wanted to stroke a 3.8, not by just getting a 4.2L block, I would get a stroker kit from Morana, he has other sizes available too, 4.0, 4.2, 4.4, and 4.6L I think are his choices, www.moranav6racing.com
 

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http://www.moranav6racing.com/stroker.html
 

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Morana is where im getting my custom cam ,chain and intake
 

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Discussion Starter · #16 ·
Wow.. :shock:

I never considered stroking to 4.6L!
 

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stroking to a 4.6 is very ####### the engine. you would have to remain NA if you went that high. 4.4 is the very most you should stroke if you get a blower, turbo or nitrous.


4.2 is just popular because you can find a F150 at a junkyard and make it cheaper
 

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Discussion Starter · #18 ·
Well, I've been thinking of putting another $5k into my V6, as opposed to trading it in for 2 more cylinders..

I want a blower if I do it, so you suggest I not consider the 4.6.. Has anyone done it that you know of?
 

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4.2 with a blower will do very well it is a good balance between total power and parts breakage. I am considering juicing mine but machine shop said 75-80 shot max unless forged pistons(at $600 a set no less) :wtf: I want to humiliate most of the trash can muffler trash around here not going for total strip but it may see some tuning there.

I'm only looking for 300HP thats double what mine was stock :shock:
 

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99vert said:
Well, I've been thinking of putting another $5k into my V6, as opposed to trading it in for 2 more cylinders..

I want a blower if I do it, so you suggest I not consider the 4.6.. Has anyone done it that you know of?
i wouldnt go above 4.2L if you get a blower. personally, you could stick w/ the 3.8 and get forged bottom end (3.8 is the only forged crankshaft) and then run a lot of boost on it.

although SSM's 4.3 block is strong enough to handle like 18psi with a non-forged crank.

basically. dont go above 4.2 if youre gonna get blown or use large nitrous (4.4L 10000% max, i just say 4.2 for safer reasons)
 
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