Another Motor swap...V8 or V6

[Tbone]

New here and I'm at the point many of you have been before...the old mighty mouse popped out a few of her innards and said goodbye, so it's time for a swap.

Straight to the point. I want to drive this pickup and I'm determined to find a way to do it. The ol 355 did well for me over the years, never topping more than a whopping 13mpg. That motor wasn't built to sip fuel, it was meant to burn it. So I'm on to options and opinions from others for some help here. She's been parked for two years and it's time to work on changing that.

I know my '84 K10 is a brick, but if I can nail down mid teens for mpg I would be content. I'm not really focused on power like I used to be. So be 100% realistic. IS 16mpg an average that is attainable out of a single cab, short box, 4wd, on 33's. Here are two options I've narrowed it down to, I'm well aware of what flack may come of this.

LS Swap, 4.8 or 5.3. It's straight forward, cheap, and makes for a reliable setup. Plenty of aftermarket.

Ford 2.7 or 3.5 Ecoboost. They make turn key standalone setups now (W/trans/T-case etc). And its not all that hard to fab up mounts.


I'll be honest, the 2.7 and 3.5, sound like crap but it's been an amazing motor in my wife's pickup. Our CCSB gets around anywhere, pulls all the little trailers we need it to, and gets very good mpg for a pickup. The LS swaps are cheap and straight forward, but am I asking for an unrealistic number from a V8? It's my number one option, it's all too easy to add a couple performance parts that get a little too carried away. And yes I plan to ditch the TH350 for an appropriate trans with OD.

Don't bother sugar coating it. If what I'm asking is bogus then just say it. I'm truly looking for your input of the two options.

 

[Midnightmoon]

There are thousands of LS swaps in just about everything from Squares to classic Camaros and everything in between. As you said, they are plentiful and cheap. That is the route to go to get your truck back on the road as quickly as possible.

With that said and with the complete disclaimer that I am a huge fan of the Ford EcoBoost platform. A gen 2 3.5L swap in to a square with a little mild tuning and you would have an absolutely killer daily driver. Plus, I am always interested in seeing something different. I'd definitely be interested in seeing a build thread if you decided to go that route.

 

[Tbone]

I completely agree it would get things going quickly. Locally there is a 5.3 with every wire needed that is ready to drop in at the snap of a finger but I just can’t seem to pull the trigger on it.

The thought of a 3.5 in there that’s cranking out over 400tq to the wheels would no doubt make this old piece of steel move out! I find myself far more drawn to doing an Ecoboost swap for two reasons….

It’s different

It’s most likely to be the option that would net the best mpg

I think more than anything I’m trying to find help talking myself out of it…

 

[Midnightmoon]

Well, you are talking with the wrong person if you are wanting someone to talk you out of it....lol My 3.5L F150 10-speed combo has just been amazing.

 

[Bextreme04]

I completely agree it would get things going quickly. Locally there is a 5.3 with every wire needed that is ready to drop in at the snap of a finger but I just can’t seem to pull the trigger on it.

The thought of a 3.5 in there that’s cranking out over 400tq to the wheels would no doubt make this old piece of steel move out! I find myself far more drawn to doing an Ecoboost swap for two reasons….

It’s different

It’s most likely to be the option that would net the best mpg

I think more than anything I’m trying to find help talking myself out of it…

My 2011 Suburban 4x4 with a 5.3/6L80e gets around 14mpg around town and up to 20mpg on the highway at 75mph. It pulls our 6k lb travel trailer at around 10mpg average and has done that all over the PNW. Its at 205,000 miles and still going strong. You can get a 5.3 with wiring harness for $800-1500 and then get a 4L80e for a few hundred more. I can't imagine a 3.5 will be economical, and will require a lot more fab and work to get going. 5.3/4l80e has all the adapters readily available to drop right in and work perfectly. I would expect just getting the engine/trans without anything else will run you double or more for the ecoboost, with no power advantage.

 

[Bennyt]

LS is ideal if you can afford it. I've yet to see anyone pull it off without spending some money on accessories, headers, oil pans, wiring, etc.

Be better off to rebuild stock motor with a good RV cam, better heads, etc. and add a FI unit to it. You'll get 2-3 mpg better probably especially with a 700r4 behind it.

3rd option is Cad 500 with an FI unit. All the torque and power you could ever want.

 

[Bextreme04]

LS is ideal if you can afford it. I've yet to see anyone pull it off without spending some money on accessories, headers, oil pans, wiring, etc.

Be better off to rebuild stock motor with a good RV cam, better heads, etc. and add a FI unit to it. You'll get 2-3 mpg better probably especially with a 700r4 behind it.

3rd option is Cad 500 with an FI unit. All the torque and power you could ever want.

Heads and EFI on the old SBC are automatically gonna push you over what an LS swap would cost. $1500 for basic rebuild of the SBC, then basic decent aluminum heads are gonna run you $2K... another $2K for the FI and you need to do all the same mods you would need for the LS on top of that including some kind of tank baffling and high pressure fuel pump. Even if you pay top dollar for a low mile 6.0/4l80 w/PCM and harness... you are still at maybe $3k. Add another $1K for all the additional fuel components, headers, and motor mounts and its pretty similar pricing with way more power and much better fuel economy and reliability. If you can get better deals on the engine/trans combo... which you usually can.. it makes even more sense.

 

[Tbone]

bextreme04 I will say that’s pretty impressive in the burb! It definitely takes a win in my book for towing as well over the Ecoboost. While they pull well they are no match for a v8 of any kind when their is weight behind them. Not in my experience at least.

Bennyt I’ve been down the small block road a few times and as much as I love them I have to be 100% honest that the LS platform is cheaper, more cost effective, and money better spent in my opinion if one is going EFI.

As of today I have found 3 options.

3.5 turnkey with trans, harness, adapter for tcase, IC and radiator. $9,500

2015 F150 wrecked but intact. $5000

5.3 as a turn key $800 trans $400

Cost effective, nod to the LS. Fastest to getting it up and going, mod to the LS.

3.5 turnkey is way over priced from when I originally looked into the idea, to a tune of $3k more.

The 2015 inclines me to consider a body swap but there is a lot more to that than a person thinks until they are in it.

 

[Bennyt]

bextreme04 I will say that’s pretty impressive in the burb! It definitely takes a win in my book for towing as well over the Ecoboost. While they pull well they are no match for a v8 of any kind when their is weight behind them. Not in my experience at least.

Bennyt I’ve been down the small block road a few times and as much as I love them I have to be 100% honest that the LS platform is cheaper, more cost effective, and money better spent in my opinion if one is going EFI.

As of today I have found 3 options.

3.5 turnkey with trans, harness, adapter for tcase, IC and radiator. $9,500

2015 F150 wrecked but intact. $5000

5.3 as a turn key $800 trans $400

Cost effective, nod to the LS. Fastest to getting it up and going, mod to the LS.

3.5 turnkey is way over priced from when I originally looked into the idea, to a tune of $3k more.

The 2015 inclines me to consider a body swap but there is a lot more to that than a person thinks until they are in it.

Yes, LS is probably best. I'm kind of an LS hater to be honest. My Suburban LTZ was an LS and it did everything well except....wow me when I opened the hood. I just think they're ugly. I still have a 400 based small block in my '63 Nova and yes it costs a bit more to build, I prefer the looks.

 

[SquareRoot]

My 85 k20 gets around 15-17 mpg. Crate 350 with a few upgrades, Edelbrock EFI and NV4500.

 

[Craig Nedrow]

I am not a fan of chevy in ford, ford in chevy. I bought a LQ4/4L80E 112000 miles, ecm, all the wires complete $1500. Wish I had gotten the steering column. Wife's 2018 GMC (6.2 6L80E) gets 13.5, towed a 5000 lb trailer from Spokane to Ellensburg area last week, right at 10 MPG. I have had at least 15 chev sixes, about a dozen SB and one BBC now in the K20. Gen three architecture is hard to beat, been making at least a million motors a year starting in 1998, which equals what everyone's say's, very available parts, cheap parts, volumetric efficiency of 90% is doable, FI so starts in the Oregon winters. Many aftermarket parts, motor mount kits, etc. and a huge knowledge base. and they don't leak. Value usually goes up on a swapped LS vehicle. Now while I do like some Fords, (up through the High Boy years), I am a Chevy guy, so biased, but at 68 years old, Chevy has been good to me, and I do all my own wrenching...Also if you LS swap, the wiring and engine bay can really be cleaned up. In Summary, the only down fall I have had with the LS, to Gen1 is....and its a biggie, (drum roll), not a good idea steam cleaning or pressure cleaning the engine bay, something I do as I like it clean, BUT the LS (all newer motors) stay amazingly clean. 2 cents.

 

[Blmpkn]

I daily drive a 2021 ranger.

If you wanna be different.. put the 2.3EB with the 10 speed behind it.

270 hp with 310 foot lbs at 3k rpm. Should get you close to 20mpg.

 

[Midnightmoon]

I daily drive a 2021 ranger.

If you wanna be different.. put the 2.3EB with the 10 speed behind it.

270 hp with 310 foot lbs at 3k rpm. Should get you close to 20mpg.

We have one of those also, 2021 Ranger crew 4x4 XLT. I wish I could tell you how it runs and drives but my daughter refuses to even let me sit in the driver's seat.....lol

These modern powertrains are amazing though. When we were young, 270hp and 300+ lb/ft would not equate anywhere near 20 mpg.

 

[Hunter79764]

I don't have swap experience on a truck yet, but I can tell you my numbers from an 85 Monte Carlo I did 10 years ago. Stock setup was 4.3 TBI, 3 speed auto (non-lockup), and 2.14 rear gears and 25-26" tires. Essentially it drives like a 4 speed that is missing first gear, or like larger tires on stock gearing. With that setup, I got ~16 city and 22-24 mpg highway (75-80 here in Texas) for a few years driving it like that. After I did a 5.3 swap with the same transmission, rear end, and tires I started getting 18-19 city but never managed to get more than 20 highway on the couple of trips I did, but I was also still romping on it quite a bit. I think that was also a tuning issue (VSS never worked right, I fought it for years before the transmission crapped out and I haven't driven it much since).

Based on that, the extra power gained quite a bit on the city stop-and-go, so that I was rarely having to really get on it to get up to speed on the onramps etc. Original MPG on the V6 TBI vs V8 carb was about the same (1 mpg less city for the V8, one MPG more highway with the 4 speed), close enough I'd call it the same. Your truck I'm guessing was factory rated at ~14 average MPG? How close to that are you getting now (or at least before it died on you)? If you have been seeing north of 12 MPG city and something reasonable (15+) highway, I would think you could get ~16 average from a 5.3 LS. I would skip the 4.8, as they tend to get the same MPG with less HP output in the newer trucks, and I'd also skip the 6.0 as they seem to drink gas in pretty much anything (3-4 MPG less than a 5.3 on a couple of late model SUV's I've got). So it seems reasonable to get your MPG goals with a stock 5.3 and a 4 speed/OD setup.

That said, a smaller engine and a turbo will almost always be more efficient at cruise and lighter throttle, while having plenty on tap when you want it. I'm not a Blue Oval guy, but other than a few early issues it sounds like the Ecoboost setups are pretty decent for reliability and longevity, and it would be a fun way to piss off people at car shows etc. I know it's not what you asked, but without seeing prices, I'm assuming the Ford swap would be a lot more money due to the novelty of it. If you were going to buy a crate 5.3 and a new rebuilt trans etc. then costs would probably be on par. Of course if you are paying someone to do the work, then cost estimates go out the window and it just depends mostly on what shop you have do it. I think you would have fun either way.

Maybe a stock cam 4.8 turbo would also fit the bill, decent MPG with 600 hp on tap when you hit the loud pedal?

 

[Tbone]

Current motor was netting me 8.5mpg, carburetor setup. All 55mph county roads to and from work. It was dyno’d at 323hp to the wheel. That was through built TH350, 3.73, and 33’s. It was a fun motor that lasted me many years. Just never practical as a backup vehicle. Made two round trips to hunting camp with it few years back at a whopping 10mpg best over 400 miles round trips.

The same motor was ran in my ‘70 for few years and through a 4L80E and 4.10’s. It was getting me 11-13 mpg city. 17 on the hwy at 65-70. 2wd pickup with 28” tire.

I’ve ran two other 350’s, both in the 4wd ‘84 and they were 9-10mpg city engines. Best 13-14 on highway at 55-60.

So carbureted and without OD, not the best option for trying to conserve some fuel. I don’t mind paying for gas but I’d like to drive more than 200 miles between fill ups.

I’m highly contemplating the 5.3 with 4l60 or 4l80. I like the 80 for durability in stock form. And after doing much research there just isn’t the swap support aftermarket for an Ecoboost into anything.

On LS swaps at how many miles is everyone freshening up the motor? I’ve got it in the shop with nothing but time on my hands.