4.2 heads on a 3.8?

LoganB

LoganB

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New Brunswick, Canada
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1997 Ford Thunderbird LX 3.8L
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I briefly heard about this and I’d like to understand it a bit better. I don’t really plan on doing it anytime soon if it ends up being a good mod since I don’t hav the money yet. I heard that the heads off of the 4.2L are virtually the same as the ones on the 3.8L. I also heard that they’re just straight bolt on to the engine. I read that they’re stronger heads but could lower your compression a tad bit. There’s just a few things I would like answered.

What would be the benefits of doing this? Any significant power gains? Airflow? Cooling? Reliability?

Have any of you tried this out yourselves? If so, what was your reason and how did you go about doing it?

What else would you pair it with? I imagine that this paired with some form of forced induction would work good, but what else?

Other than that I guess I’d be curious about how expensive a mod like this costed you (if you’ve tried it) and what kind of power you were pushing after it all.

Again this is just my curiosity since I briefly got told about this at work the other day and wanted to see if anyone had tried it
 
I believe the 4.2 heads are the same or similar to the 3.8 split port heads. Seems like the Mustang 3.8 split port heads and intake with a 4.2 bottom end would be a pretty good combo if you stayed V6. I'm sure there is a ton of information out there if you search for split port head swap or something like that.
 
The 4.2 was only available as a split-port motor. All the split-port heads are the same, regardless of whether they were on a 3.8, 3.9, or 4.2. Running the split-port heads requires the matching split-port intake manifold, either from a Mustang, or a Windstar. Externally, the 3.8 and 4.2 engines are identical, except for the intake manifold, so if you were looking for more power, your best bet would be to buy a complete 4.2, and a Mustang intake manifold, and swap out that setup for your existing 3.8.
 
1997ThunderbirdLXV6 said:
the word "Windstar". Such a turn-off. I mean factually correct, but still...ew.
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Oh come on 97.... isn't this the sexiest, most desirable vehicle you have EVER SEEN?!!!!

1754163541617.png

"A hunk, a hunk of burning love, ah (ah)"

I think I just threw up.
 
MadMikeyL said:
... so if you were looking for more power, your best bet would be to buy a complete 4.2, and a Mustang intake manifold, and swap out that setup for your existing 3.8.
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And if you were to replace your 3.8l, I would say just go with a 4.6l and be done with it. That is, if you were going to spend the money and time and did not already have a 4.2l waiting to use.
 
1997ThunderbirdLXV6 said:
I find it funny how anytime the split-port conversation comes up, inevitably someone utters the word "Windstar". Such a turn-off. I mean factually correct, but still...ew.
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Hey I had a 2001 model and it was decent AFTER I cleaned the egr system and put one of those harbor freight inline compressed air oil filter in the pcv line. They had a recall on the valve cover baffle not working but my inline filter did the trick. At 200k the trans started slipping and water pump started pouring so I sent it to the crusher. I really liked the dual sliding doors w/ captain chairs in back.
 
White Lincoln said:
And if you were to replace your 3.8l, I would say just go with a 4.6l and be done with it. That is, if you were going to spend the money and time and did not already have a 4.2l waiting to use.
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The 4.6 swap is a lot more involved. The trans is different, all the wiring has to be changed, the computer has to be changed. Really you need a complete donor car to do it. However a 4.2 swap would be pretty straightforward, and would get you similar hp for a lot less aggravation. If I had a clean 3.8 car, it would definitely get a 4.2 before it got a V8 swap.
 
I did a splitport swap and a windstar intake swap. The windstar intake is rediculiously tall. IIRC, the hardest part was converting the fuel rail to returnless

The engine itself post splitport and windstar intake sounded cool but wasn't that great. Had I done this again, instead of going 5.0 V8, I would/should have bought a 4.2L longblock from an F150/E150 instead. I would have gotten better fuel economy (which matters for endurance racing) and 100-150LBs less weight than my tbird in its final form.
gunn

Thread 'Gunn's 3.8L Single Port to Splitport V6 DIY'

S4Gunn's Split-port DIY & Lessons Learned


Q: Why do a splitport upgrade? For starters, a 99-04 Mustang is rated for 193HP/225lb-ft while the same 3.8L block in the 89-97 Mustang only made 140HP/215lb-ft of torque. Given that V6 Mustangs are plentiful, the parts are cheap so this is one of the best bangs for the buck you find find.

In my case, I needed a cheap yet reliable way to boost the HP of my 24 Hours of Lemons track car (they give you a residual after every race so I made my intentions clear to the judges). Plus, I also didn’t want to upset the weight & balance of my track...
 
MadMikeyL said:
The 4.6 swap is a lot more involved. The trans is different, all the wiring has to be changed, the computer has to be changed. Really you need a complete donor car to do it. However a 4.2 swap would be pretty straightforward, and would get you similar hp for a lot less aggravation. If I had a clean 3.8 car, it would definitely get a 4.2 before it got a V8 swap.
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You are correct. I got to thinking about what I said and what you said and remembered why I have not done it. As you said, you will need a 4.6l tranny and drive shaft along with the computer to boot. So, a better comment would have been "it might be cheaper or easier to buy another Thunderbird". :P
 
There was a local kid a while back who had a boosted v6 with a windstar intake. The car made good power for a v6
 
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