New Build: GM 4.2L Atlas into '91 FJ80

[TwoTonic]

Atlas Fuel Economy

mpg??

With the I-5, now having put about 15K miles on the swap and fully breaking in the motor, we're seeing a blended (city/hwy/commuting) increase in fuel economy of about 45%.

Or, the way I put it is that with the 3FE, commuting across town 12 miles to work, I'd invariably get between 190 and 205 miles on a tank of 87 octane Regular to the point where the "Yellow Light Comes On". Now, same route, same conditions, I'll get between 295 and 310 miles. About an extra 100 miles per tank.

In country driving, driving 65MPH across the desert to the ski area-- straight up highway driving, I'd typically get 280-290 miles before the light came on with the 3FE. Now I can get about 390-395, once in awhile touch 400 before the light comes on.

So overall, it's easiest to encapsulate it as "I get an extra 100 miles out of every tank". Highway driving used to be 14MPG and now it's 19-20. Commuting used to be 10-11MPG and now it's 15MPG.

It's still not exactly a Prius, but with gas destined for $3-4 a gallon forever, I'll take the extra 100 miles per tank. It actually won't take long to pay for the swap.

Not sure what I'll get with the 4.2L, but I think with taller ratios I can get as good or even slightly better. The Atlas torque curve is very, very flat-- I think they'll pull taller gears than the 4.10s to eek out a little better mileage.

 

[Moby]

I have no input of value except to say that I need more landcruisers. My FJ-62 has a hotrod 2FE that is about to get a programmable MAF conversion and an H55F. But the I5/I6 or an ERod LS3 swaps are so appealing that I almost can't pull the trigger on the H55F. The only solution appears to be buying more landcruisers so that I can do all the swaps/hotrodding that I want to do

 

[TwoTonic]

I have no input of value except to say that I need more landcruisers. My FJ-62 has a hotrod 2FE that is about to get a programmable MAF conversion and an H55F. But the I5/I6 or an ERod LS3 swaps are so appealing that I almost can't pull the trigger on the H55F. The only solution appears to be buying more landcruisers so that I can do all the swaps/hotrodding that I want to do

Ah, it's a slippery slope, isn't it?
I'm still looking at this Duramax and the FZJ I want to put it in...

 

[KliersLC]

It is hard to tell from the pic, but are you sure this will clear when the Passenger side wheel is stuffed?

 

[TwoTonic]

It is hard to tell from the pic, but are you sure this will clear when the Passenger side wheel is stuffed?

On the Atlas it's fine because the truck sits about 2.5" higher, due to taking about 450+ pounds off the nose!

Actually, for an off-road truck we'd always recommend a lift for that reason.

 

[locrwln1]

nice swap. Would it be worth swapping out a 1FZ-FE with an Atlas and a GM transmission? Just curious!

Torque on both motors is the same, but you gain a ton of hp. The Atlas is rated for 275hp and it pulls from idle to it's 6k redline. Once you get above 4k, the VVT kicks in and it just keeps on pulling. Great motor, just not sure if it would be "worth it" for a good running 1fze, but if you had one that was bad, then it might be a good choice.

I really enjoyed my TB with the 4.2. I always felt let down when I would jump into my LC. Plus I averaged 20mpg in my TB driving it like I stole it. The worst I ever got was 17-18mpg driving from Reno to Las Vegas at shall we say elevated speeds.

Jack

 

[Nay]

Torque on both motors is the same, but you gain a ton of hp. The Atlas is rated for 275hp and it pulls from idle to it's 6k redline. Once you get above 4k, the VVT kicks in and it just keeps on pulling. Great motor, just not sure if it would be "worth it" for a good running 1fze, but if you had one that was bad, then it might be a good choice.

I really enjoyed my TB with the 4.2. I always felt let down when I would jump into my LC. Plus I averaged 20mpg in my TB driving it like I stole it. The worst I ever got was 17-18mpg driving from Reno to Las Vegas at shall we say elevated speeds.

Jack

I think the interesting question is whether it is "enough" for an 80 vs. a V8 swap, and how much weight you have and/or mpg you would gain over a V8 swap. And whether it is substantially less expensive due to engine availability.

Our engines are just so inefficient and if you keep an 80 relatively light they aren't that heavy. Adding to that if across the board you can achieve an 6%-8% weight reduction by swapping in a 4.2 and GM tranny that is going to only add to the benefits, plus you have essentially endless parts availability.

I'm pretty interested to see the outputs on this one. I like the 1ZFE, but it is such a dog at elevation, around here you want an engine that is going to pull through 4K without having to rely on second gear to get there, and I've never thought the 1ZFE is particularly NVH friendly above 3K.

More to think about as I want to do a swap in a couple of years when I hopefully have some more time and funds to put it in motion.

 

[Moby]

For both the I-5 and this swap, what are you doing for the fuel system? Do the Atlas motors need the ~65 psi that Gen III\IV LS motors do?

 

[TwoTonic]

For both the I-5 and this swap, what are you doing for the fuel system? Do the Atlas motors need the ~65 psi that Gen III\IV LS motors do?

For the I-5 we ended up putting a GM pump in the tank and that's worked really well, other than that it was a pain-in-the-sender to do. The engines do need approx 60-65 at the rail.

Haven't made a final decision on the 4.2 yet-- hoping for an easier-to-do option.

I'll post when we figure it out.

TT

 

[Moby]

For the I-5 we ended up putting a GM pump in the tank and that's worked really well, other than that it was a pain-in-the-sender to do. The engines do need approx 60-65 at the rail.

Haven't made a final decision on the 4.2 yet-- hoping for an easier-to-do option.

I'll post when we figure it out.

TT

Was it a pain to pull the tank and make the in tank pump fit or was the pain in something else like new lines or GM push connector (which I assume that the Atlas uses)?

 

[warpdriv]

I'm ready to see some TT mad fab skills!!! Subscribed!

 

[TwoTonic]

Was it a pain to pull the tank and make the in tank pump fit or was the pain in something else like new lines or GM push connector (which I assume that the Atlas uses)?

Was mainly just the time-and-trouble to empty, pull the tank, finesse the GM unit into it (was a tight fit) and get it all sealed up nicely.

Given that the Toyota system was
a) working
b) capable of putting 50-60# on the rail already and
c) already set-up for return line...

it seemed like a lot of zero-return effort. It works fine, but there has to be an easier way that leverages the existing Toyota system pieces.

TT

 

[TwoTonic]

I'm ready to see some TT mad fab skills!!! Subscribed!

Hey, Jeff. Yeah, "fab skills". Right. I have an MS degree-- "Madman wif a Sawz-All".

There's a great guy over on TrailVoy who's shoe-horned the Atlas 4.2 into a Supra (!) though... Compared to that, this will be a cruise down Main Street Moab.

We'll post as we go--- still gathering a few parts for the mad dash to get it assembled.

 

[TwoTonic]

I think the interesting question is whether it is "enough" for an 80 vs. a V8 swap, and how much weight you have and/or mpg you would gain over a V8 swap. And whether it is substantially less expensive due to engine availability.

Our engines are just so inefficient and if you keep an 80 relatively light they aren't that heavy. Adding to that if across the board you can achieve an 6%-8% weight reduction by swapping in a 4.2 and GM tranny that is going to only add to the benefits, plus you have essentially endless parts availability.

I'm pretty interested to see the outputs on this one. I like the 1ZFE, but it is such a dog at elevation, around here you want an engine that is going to pull through 4K without having to rely on second gear to get there, and I've never thought the 1ZFE is particularly NVH friendly above 3K.

More to think about as I want to do a swap in a couple of years when I hopefully have some more time and funds to put it in motion.

No arguments from this quarter-- If you have a perfectly good 1Z motor, there's probably no point in swapping out just to save the pounds and gain some power. On the other hand, there have been owners kind of getting to the end of life for their factory motors and wondering which way to go: Trade-it-in versus rebuild-the-1Z versus swap-to-something-with-more-power.

The I-6 Atlas nets more power, with better fuel economy, in an engine that's probably $400 at your local wrecking yard... so I'd suggest it's worth at least looking at while considering $5000-7000 for a rebuilt 1Z.

For us guys afflicted with early Fj80s with the 3FE, the math gets easier, a lighter, quicker, more powerful truck with an Atlas seems like an easier call.
60% more power, 40% better economy and 400# lighter. If gas stays above $3 a gallon (which seems likely now that OPEC has made us their beech), the fuel savings alone are pretty compelling on a 3FE truck.

Right now I'm anxious to do a comparison of the 3.7L to the 4.2L on power and economy-- I'm pretty sure I'll like the 4.2 better for towing but talk to me after a visit to the gas pump!

TT

 

[Nay]

No arguments from this quarter-- If you have a perfectly good 1Z motor, there's probably no point in swapping out just to save the pounds and gain some power. On the other hand, there have been owners kind of getting to the end of life for their factory motors and wondering which way to go: Trade-it-in versus rebuild-the-1Z versus swap-to-something-with-more-power.

The I-6 Atlas nets more power, with better fuel economy, in an engine that's probably $400 at your local wrecking yard... so I'd suggest it's worth at least looking at while considering $5000-7000 for a rebuilt 1Z.

For us guys afflicted with early Fj80s with the 3FE, the math gets easier, a lighter, quicker, more powerful truck with an Atlas seems like an easier call.
60% more power, 40% better economy and 400# lighter. If gas stays above $3 a gallon (which seems likely now that OPEC has made us their beech), the fuel savings alone are pretty compelling on a 3FE truck.

Right now I'm anxious to do a comparison of the 3.7L to the 4.2L on power and economy-- I'm pretty sure I'll like the 4.2 better for towing but talk to me after a visit to the gas pump!

TT

Just picking back up this thread...and bumping for updates

I was coming at this from the other direction, which is the idea that the 4.2 Atlas may be enough power to forgo a V8, with better weight (?) and efficiency (?) than the V8 platforms.

I love inline six engines, but I am not as enthralled by the 1ZFE as many are - it has its great attributes, but the engine does sucks eggs at altitude and pays you back with dismal fuel economy. It also has a surprisingly narrow band of optimal NVH to power, somewhere around 2,400-3,000 RPM.

So it's great if you can keep your RPM in that range, but that's not easy when you are so underpowered.

A 291 hp / 275 lb/ft engine with a V8 torque curve that puts you in the 18-20 mpg range (if reports here are true) is incredible. This is, in many ways, what we wish our 1ZFE's would be.

I suppose the reality for me is altitude turns my 1ZFE into a 3FE and I need an engine that is far more efficient throughout the power range. V8 would be great and a big I6 is not easy to fit...but we already have one of those ...and my gut sense is an I6 replacement would really keep the "feel" of the rig.

I'm very interested to see how this turns out and what it costs. There is ultimately little point if a V8 can be done at the same cost and near same fuel economy, but that's really the question.

Hope to see it become reality.

 

[lrowe_csp]

Very interesting. I have 235K 97 FZJ and I am weighing rebuild vs some type of conversion in the spring. I will follow this thread closely!

 

[locrwln1]

Just picking back up this thread...and bumping for updates

I was coming at this from the other direction, which is the idea that the 4.2 Atlas may be enough power to forgo a V8, with better weight (?) and efficiency (?) than the V8 platforms.

I love inline six engines, but I am not as enthralled by the 1ZFE as many are - it has its great attributes, but the engine does sucks eggs at altitude and pays you back with dismal fuel economy. It also has a surprisingly narrow band of optimal NVH to power, somewhere around 2,400-3,000 RPM.

So it's great if you can keep your RPM in that range, but that's not easy when you are so underpowered.

A 291 hp / 275 lb/ft engine with a V8 torque curve that puts you in the 18-20 mpg range (if reports here are true) is incredible. This is, in many ways, what we wish our 1ZFE's would be.

I suppose the reality for me is altitude turns my 1ZFE into a 3FE and I need an engine that is far more efficient throughout the power range. V8 would be great and a big I6 is not easy to fit...but we already have one of those ...and my gut sense is an I6 replacement would really keep the "feel" of the rig.

I'm very interested to see how this turns out and what it costs. There is ultimately little point if a V8 can be done at the same cost and near same fuel economy, but that's really the question.

Hope to see it become reality.

I'm with you, I don't love the 1fze either, I think it was a decent motor in it's day (maybe). But as you pointed out, crappy power and crappy mileage aren't very endearing. I can deal with one or the other, but being penalized both ways kind of sucks.

I knew of another trailblazer with the 4.2, it was the extended version, so bigger/heavier than the regular TB. I spoke with two guys that drove that one and they didn't think too much of it hauliing the extra weight around. Both were company trucks and were pretty much always loaded with a couple of hundred pounds in the cargo area. These were both 275hp trucks. I really liked mine and thought it did great, so it will be interesting to see what the OP thinks of it in a LC.

Jack

 

[TwoTonic]

Just picking back up this thread...and bumping for updates

I was coming at this from the other direction, which is the idea that the 4.2 Atlas may be enough power to forgo a V8, with better weight (?) and efficiency (?) than the V8 platforms.

I love inline six engines, but I am not as enthralled by the 1ZFE as many are - it has its great attributes, but the engine does sucks eggs at altitude and pays you back with dismal fuel economy. It also has a surprisingly narrow band of optimal NVH to power, somewhere around 2,400-3,000 RPM.

So it's great if you can keep your RPM in that range, but that's not easy when you are so underpowered.

A 291 hp / 275 lb/ft engine with a V8 torque curve that puts you in the 18-20 mpg range (if reports here are true) is incredible. This is, in many ways, what we wish our 1ZFE's would be.

I suppose the reality for me is altitude turns my 1ZFE into a 3FE and I need an engine that is far more efficient throughout the power range. V8 would be great and a big I6 is not easy to fit...but we already have one of those ...and my gut sense is an I6 replacement would really keep the "feel" of the rig.

I'm very interested to see how this turns out and what it costs. There is ultimately little point if a V8 can be done at the same cost and near same fuel economy, but that's really the question.

Hope to see it become reality.

Hey, I LOVE putting V8s in stuff that didn't have it in their first iteration (we put an LS6 in a Datsun 280Z conversion awhile back and well, there's that BMW wagon with the "357i" logo on the back with an LQ truck motor in it... Pics are here: Picasa Web Albums - TL Care - BMW 357i Spor... ), but like the I-6 for its 'respect' for the Cruiser heritage. In theory the original F was an 'homage' (copycat) by toyota of the original GM I-6 235 engine anyway, so dropping an Atlas 6 in sort of brings it full circle.

There are several things that are nice about the I-6 for the application, even as much as I love the LS/LQ series of Gen III and IV V8s>
1) It fits a lot better. With a swapped pan, the Atlas just looks like it belongs there... exhaust is easy, no cross-overs, no steering shaft interference, even the mechanical clutch fan on the I6 nuzzles against the radiator in the right spot.
2) It's substantially lighter. Most everybody looking at GM V8s will gravitate to the LQ iron-block series for cost reasons (the AL block engines get a big price premium due to being "Corvette" motors or something. I like the 300HP of the 5.3L V8 just as well as an F-Body's LS1... and like to save $2500.)
3) The torque curve is dead flat. With VVT and those heads, the Atlas torque curve is amazing... even flatter than a 5.3 or 6.0 V8. This is great for off-road, and towing, and fuel economy. You basically get full torque from just off idle all the way to 6300 RPM. This is a huge advantage over the 3FE or 1Z motors, which have a fairly narrow 'sweet spot'... True, the 3FE peaks at 220 ft-lbs, but that's a narrow peak and the induction system is out of breath by 4000, which is about where the Atlas kicks in with VVT. I'll take the "area under the curve" of the I5 any day! And this gets scaled up 20% on the I-6.
4) Better fuel economy than any of the 5.3s or 6.0s. You basically get the power of a V8 out of an I-6.

Even in the Trailblazer/Envoy family GM eventually realized what they had... for awhile, early in the product life, they actually offered the 5.3, but when they freshened the Atlas to 290HP it became pointless and they dropped the 5.3... If you wanted the ultimate in power you got the TBSS with the LS2 in it.

The heads on the Atlas motors are amazing for the way they flow and, with the VVT, I find that the altitude just bothers the engine less than the 3FE lost power. My tan Cruiser with the 3.7L I-5 lives at 6000 feet and still makes great power... not as good as a turbo obviously, but I think the induction system of the Atlas does a great job at altitude.


We're about due to hit the 'sprint' stage on this build. All the test fits are done and we've just been gathering components needed to finish it without a lot of waiting. I'll post progress next week, once the mounts and adapters are ready to go.

TT

 

[TwoTonic]

I'm with you, I don't love the 1fze either, I think it was a decent motor in it's day (maybe). But as you pointed out, crappy power and crappy mileage aren't very endearing. I can deal with one or the other, but being penalized both ways kind of sucks.

I knew of another trailblazer with the 4.2, it was the extended version, so bigger/heavier than the regular TB. I spoke with two guys that drove that one and they didn't think too much of it hauliing the extra weight around. Both were company trucks and were pretty much always loaded with a couple of hundred pounds in the cargo area. These were both 275hp trucks. I really liked mine and thought it did great, so it will be interesting to see what the OP thinks of it in a LC.

Jack

The 1FZ motor certainly had a lot of great points... and was a big step up from 40 years of the F motor's evolution. But, 212 HP just isn't that much anymore. I think the entry level, base package Altima has more power than that these days. I think the good news is that we all love the trucks, but many of us are looking for "more" out of a powerplant-- and more power and more fuel economy (with less weight, which is a real Atlas advantage) add up to what we think will be a winner. I'm planning on driving the Atlas Cruiser another 25 years so think it deserves a powerplant for the 21st Century. Maybe someday they'll perfect the Hybrid AWD power system and we'll be transplanting hybrid drivelines into them someday...

 

[Nay]

but like the I-6 for its 'respect' for the Cruiser heritage. In theory the original F was an 'homage' (copycat) by toyota of the original GM I-6 235 engine anyway, so dropping an Atlas 6 in sort of brings it full circle.

That is a big appeal for me as well. After spending years driving a Chrysler 4.0, one of the things I loved about the 80 was the inline six. They just feel right in a true 4x4 that will see everything, but you want power and economy for the next 15 years.

The torque curve is dead flat. With VVT and those heads, the Atlas torque curve is amazing... even flatter than a 5.3 or 6.0 V8. This is great for off-road, and towing, and fuel economy. You basically get full torque from just off idle all the way to 6300 RPM. This is a huge advantage over the 3FE or 1Z motors, which have a fairly narrow 'sweet spot'... True, the 3FE peaks at 220 ft-lbs, but that's a narrow peak and the induction system is out of breath by 4000, which is about where the Atlas kicks in with VVT.

The heads on the Atlas motors are amazing for the way they flow and, with the VVT, I find that the altitude just bothers the engine less than the 3FE lost power. My tan Cruiser with the 3.7L I-5 lives at 6000 feet and still makes great power... not as good as a turbo obviously, but I think the induction system of the Atlas does a great job at altitude.

This is what I need. Love the I6 offroad, always have, and we take a step up here. I need flat power that can breathe - my 80 is kept intentionally light and with shaving some 300 or more lbs I would be at near stock weight except for my tires.

The narrow sweet spot of the 1ZFE is I think one of its most surprising negative features. You want to step down a gear ratio to 5.29, and you consistently push 3K RPM at highway cruising speed, which should be smooth as silk and quiet but it isn't. Drop much in RPM at altitude and the the power isn't there. You'd never accept such a narrow range of performance in any modern engine.

I want an engine that is breathing effortlessly at 4K for those longer steep uphills at 9K+ feet elevation without giving up all the offroad feel of the I6. Pretty excited to see this one come together, I've always balked at a V8 swap for some reason, but the idea of a 21st century I6 with the features of the 4.2 has so much appeal.

I'll shut up and watch the progress