Leveling my engine conversion FJ80 (1 Viewer)

[TwoTonic]

We completed an engine swap into a '91 FJ80 recently. We installed an Atlas I-5 from a Hummer H3... Although this may seem like a strange combo, it's actually worked out pretty well. The Hummer motor has 60% more power, 40% more torque, gets 30% better fuel economy and is quieter. Being a more compact engine, the fit was a breeze-- Being an I-5, there was no steering linkage or brake booster interference. It fits really well.

Here is a link to an album for the conversion-

Picasa Web Albums - HT - Hummer H3 Dri...

The one side-effect of the conversion is that the truck is a lot lighter-- we took about 200# off the nose. Are there suggestions as to whether we should cut down the front springs to lower the front a bit? Or, is it better to put a lift set-up or longer springs in the back. I actually like the clearance on the front, but it does look funny with the nose high. We actually didn't realize that the weight reduction would have such an impact until we had the engine conversion done and stopped to think about how much lighter than all-aluminum block-and-heads GM motor was. The case on the 4L70E is much lighter, too.

I've attached a photo of the rig... Any ideas on the best way to level it?

Thanks,
TwoTonic

 

[MLX450]

Nice work there! Add an ARB bumper and a winch, that should give you some weight in the front.
Where did you get those front seats? , and more info on the conversion, please

 

[MoJ]

What's the difference in height front to back? I wouldn't cut the coils. Look at adding height to the rear via different coils or adding coil spacers. If the difference is around 1" spacers would be the inexpensive way to do it.

 

[Atoyot1031]

You could level it fairly easily with the right set of OME springs. Light in the front, medium or heavy in the rear.

Nice conversion. What is the rest of the drivetrain? What is the displacement of the motor and published output?

Welcome to Mud

 

[Lka1988]

That's a pretty clean conversion. The I5 is only 3.7L. How does it hold up to a loaded truck?

 

[Lka1988]

I just googled the specs for the 3.7L: 242HP @ 5600 RPM, and 242 lb/ft @ 4600 RPM.

A stock 3FE puts out 155HP @ 4000 RPM, 220 lb/ft @ 3000 RPM. Lower RPM for max torque, but the 3.7 puts out more overall.

I'd be interested to see a dyno chart for the 3.7.

 

[mmml4]

You could swap in a pair of later model springs. IIRC the 93-97 springs are about two inches shorter than the 91-92. I am using a set of each for a build I am doing and one set is about 17" and the other is about 19".

 

[jeepocabra]

You could always lift the rear a tad with ome springs.

I have questions about your swap, mostly about the transmition.

How did you retain the stock shifter.

Also were you able to retain the use of the shift indicator in the dash, and the other gauge functions.

 

[TwoTonic]

Eye-balling it, I think we're about 2" high in the front (or, 2" low in the back). Where it looks really funny is to put a trailer on the hitch with 300-400# of tongue weight. Makes the thing look like headlights are pointed at the starts. I think we'll play with adding height in the back, probably with stiffer springs to start and some spacers. I have other tow rigs but I'll use this to pull 'toy' trailers once in awhile.

We got about 240,000 miles out of the 3FE before starting the conversion. That motor was still tight, but it hadn't gotten any more powerful after its 200,000 mile break-in period.

The Atlas I-5 is part of the GM platform used in the H3/Canyon/Trailblazer/Colorado/Envoy families. The H3 got the 5-cylinder and the plusher trucks got the 6-cylinder version.

We used a Mark's Adapter kit from the output shaft of the GM4L70E and it bolted up very easily. Retained the stock Cruiser transfer case. The gearing in 1st for the GM transmission is low enough that, in LOW Range, it will be reasonable off-road. Front and rear gears are the stock 4.11s.

We used the stock GM engine control PCM, which controls both the I-5 and the 4L70 transmission.
Tuning, other than turning off all the unused stuff (VATS security, fancy dash indicators), is pretty much stock all the way. We used a K&N air filter which might be good for a few HP. Cats were retained, of course, and emissions are ultra-low-- another plus over the old 3FE.

In practice, the power difference is stunning. I have one particular grade that I drive all the time-- the 3FE would be panting at 48MPH with my foot planted firmly on the floor-- the Atlas easily pulls to 75MPH. Having owned 93-97 FJ80s, this thing will run rings around a stock '96 with the 1FZ (which was spec'd at 212HP).

The big pick-up (in addition to driveability, of course) is in fuel economy. On the road, I drive a 300 mile mountain/freeway/town loop pretty often... driving the speed limit with the 3FE would net me about 13 MPG. With the new Atlas motor, I can regularly exceed 19.5.

I'm pretty happy with how it turned out-- better power, better torque, quieter, and much improved fuel economy. I think it's a great conversion for a daily driver-- which can still be taken off-road once in awhile.

 

[TwoTonic]

You could level it fairly easily with the right set of OME springs. Light in the front, medium or heavy in the rear.

Nice conversion. What is the rest of the drivetrain? What is the displacement of the motor and published output?

Welcome to Mud

The Atlas is a 3.7L in a 5-cylinder form (H3) and 4.2L in 6-cylinder.
At 242/242 it trounces the 3FE and breathes better (with VVT) than the 1FZ-- Way more power where you can use it than the 1FZ.

I have another FJ80 that we are planning to put an LT1 into-- I'd like to compare the two. The fuel economy on this Atlas is a big plus.

 

[TwoTonic]

You could always lift the rear a tad with ome springs.

I have questions about your swap, mostly about the transmition.

How did you retain the stock shifter.

Also were you able to retain the use of the shift indicator in the dash, and the other gauge functions.

We ended up using the Hummer shifter, which includes a gear position indicator in it's mechanical sweep. We did sacrifice the dashboard lights for gearing (although I'm planning to add that back in when we do the tach upgrade.)

The Hummer shifter is all electronically-controlled and it wires directly to the PCM. The throttle is, likeways, all electronic-- it's an E-Pedal. I wasn't sure I would like that, but it rocks relative to the ancient transmission control in the 3FE and Toyota transmission set-up. E-throttle means much quicker downshifts and no 'hunting' to figure out the right gear selection-- it's one of the advantages of leveraging the GM tuning and engine control-- smooth shifts and you NEVER have the feeling you are in the 'wrong' gear. It drives really well.

 

[TwoTonic]

Nice work there! Add an ARB bumper and a winch, that should give you some weight in the front.
Where did you get those front seats? , and more info on the conversion, please

Thanks!

The front seats were out of a Saab 9-3 Turbo. We found them in a Saab specialist wrecking yard in LA... they were in awesome shape.

With power and heat, the seats dress it up nicely and are very functional.... we looked a long time to find some seats "thin" enough to fit in there. There isn't much height to work with the way the stock seats are mounted in an FJ80. The width is just right too, so we didn't have to mess with the console.
We made a set of custom brackets and they mounted well.

The second and third row seats are honest Toyota seats out of a wrecked Lexus LX450. They bolted right in, after swapping the seat belt tensioners too (which, oddly, are different between the Toyota Lexus versions )

 

[sandcruiser]

OME springs in the rear would lift you up. Or even just a simple spacer-ring. 1" rings are darn cheap. Then add a bumper or a 2nd battery and you should be close to level again.

 

[Lka1988]

The Atlas is a 3.7L in a 5-cylinder form (H3) and 4.2L in 6-cylinder.
At 242/242 it trounces the 3FE and breathes better (with VVT) than the 1FZ-- Way more power where you can use it than the 1FZ.

I have another FJ80 that we are planning to put an LT1 into-- I'd like to compare the two. The fuel economy on this Atlas is a big plus.

I still want to see how well it holds up with a loaded truck.

 

[TwoTonic]

I still want to see how well it holds up with a loaded truck.

We did haul a buddy's boat up over the hill a couple of times already. It's got plenty of grunt with a big boat on-- and will take Cat Creek Summit at 75, which the 3FE could only do 48 on. I think it's got more usable power than the 1FZ, I'm convinced. Beyond that, though, only the dyno will tell the story.

Come up over the Idaho line and we'll compare. Or, I'll bring it down to SLC sometime to put on an AWD chassis dyno?

 

[AKcruiserfreak]

Very cool! Thinkin ouside the box. I can't believe people are ragging you about power considering the 3FE's reputation as a complete dog. Whatever. I'm curious what your MPG's are.

TK

 

[bpassmore]

I love creativity, so I love this conversion. Good job!

 

[TwoTonic]

I used to comment on the 3FE in my 91's in the context of how much of the time (in town, up mountains, up hills, up slight inclines) I'd have to have my foot clear to the floor to get it to move.

With the Atlas engine, I'm averaging 19.7MPG on a 300 miles town/country/interstate loop. I can get repeatedly north of 20 MPG on the country portions, which in this state have a 65 MPH speed limit. This compares to 12-14 with the same route in the same truck and the 3FE.

I was giggling the first time I drove it with the Atlas I-5, between being so much lower weight and having a more powerful motor, plus willingness to rev. It just felt a LOT lighter and quicker. Immensely so.

No offense taken on the power questions-- I admit that it's a non-obvious conversion. But, we are really happy with it. If I was towing more I'd have probably done the I-6 in the same architecture-- 275HP, 270 TQ-- and given up a little fuel economy. But this is ideal for a mountain truck and daily driver-- we've taken it skiing a lot with the family's gear, hauling kids to school in the snow, mileage is great, it's quiet.

These motors are cheap-- there's a good used one on Ebay right now for under $500 with low miles-- and the GM tuning brings it very up to date, especially with variable valve timing. It really takes off when it comes up on cam. Toyota's 'F" series motors were a fine design 40 years ago, but in this truck we wanted an updated drivetrain with the solid quality only the FJ series have. It's a nice combo.

TT

 

[TwoTonic]

What's the difference in height front to back? I wouldn't cut the coils. Look at adding height to the rear via different coils or adding coil spacers. If the difference is around 1" spacers would be the inexpensive way to do it.

Just measured the height disparity... it's exactly 2 inches higher in the front-- unladen.

 

[ThePookieBear]

Wow. I find this very interesting. Sorry if I missed it from the pictures, but what did you do with the engine and transmission mounts? Were you able to utilize the stock one? And was Marks kit specifically for this engine/tranny combo, or was it for the tranny?