Atlas 3500/3700/4200 engines, give me the good, the bad, and the ugly

[Lil'John]

Title basically states it. I'm looking for any/all thoughts from "longevity" to swapping.

I find the all aluminum construction to be intriguing.

The numbers on them is interesting:
4200(LL8) 270hp and 275 ft-lbs
3700(LLR) 242hp and 242 ft-lbs
3500(L52) 220hp and 225 ft-lbs

They are tunable with HP tuners and maybe others.

There appears to be a lack of aftermarket support. Maybe a minor issue but they also appear to all be rear sump(???)

They appear to be 4l60e autos only. My quick searching didn't show them coming with a manual transmission. Is a manual trans possible?

 

[06h3]

AR5 manual trans bolts up to it. They were in H3s maybe Colorado’s?

 

[Lil'John]

AR5 manual trans bolts up to it. They were in H3s maybe Colorado’s?

Thanks for the bread crumb. To put some more info on this option:
2004 to 2008– Chevrolet Colorado
2004 to 2008– GMC Canyon
2006 to 2010– Hummer H3

Gear ratios (Canyon, Colorado, H3):

1	2	3	4	5	R
3.75	2.26	1.37	1.00	0.73	3.67

And to put some info on the engines:
3500(L52):
2004–2006 Chevrolet Colorado
2004–2006 GMC Canyon
2006 Hummer H3
3700(LLR):
2007–2012 Chevrolet Colorado
2007–2012 GMC Canyon
2007–2010 Hummer H3
4200(LL8):
2002–2009 GMC Envoy, Envoy XL, and Envoy XUV
2002–2009 Chevrolet TrailBlazer and TrailBlazer EXT
2002–2004 Oldsmobile Bravada
2004–2007 Buick Rainier
2005–2009 Saab 9-7X 4.2i

Is the bellhousing pattern the same between them all?

 

[Mattygwheeler]

This guy has some good tech on the atlas class motors

 

[06h3]

I will chime in more soon. Busy morning with work. I have many opinions since this was a motor I had in my H3.

 

[Lil'John]

This guy has some good tech on the atlas class motors

One of my favorite channels when Holdener isn't doing 2 hour videos 10-20 minutes of super hyper is handlable... 60 minutes not so much. In fact, it was his 4200 series of videos that made me want to look a bit more into it with "real" people.

I will chime in more soon. Busy morning with work. I have many opinions since this was a motor I had in my H3.

Any information you could provide would be greatly appreciated.

 

[u2slow]

I kept watching his vids thru breaking all the head bolts on removal

I too was interested in this engine over a decade ago. I had trucks with the old 250 and 292 6's. Glad I slid over into 6BT land instead.

 

[Lil'John]

I kept watching his vids thru breaking all the head bolts on removal

I too was interested in this engine over a decade ago. I had trucks with the old 250 and 292 6's. Glad I slid over into 6BT land instead.

I'll have to go rewatch his videos.

I can't go with 6BT... too big and too costly. I love the I pulled this 500k mile 6BT out and I want $5k for a long block ads

 

[TRINDU]

I never cared about the 4/5 atlas as the ecotec are more popular and widely supported. There was a fault to the 4200 heads, something about valve seats. Although it's not uncommon to find them 200k+.

GM pulled a Ford and the atlas bell doesnt share a pattern with the rest of the GM family. However, the AR5 is nothing more than a R150/AX15 so you're manual trans/tcase options are plentiful.

 

[JohnnyJ]

I know Holdener mentions it in his videos, but I'd look for the later engines with 58x/4x sensors. This puts them more consistent with Gen4 LS motors and likely opens up more options for fuel injection.

And I agree, I like the 10-15 min Hodener videos, but his marathon videos are too much for my attention span.

Also, found this when googling for transmission options: Bell housing adapter - EMTECH MOTORSPORTS

 

[Lil'John]

I never cared about the 4/5 atlas as the ecotec are more popular and widely supported. There was a fault to the 4200 heads, something about valve seats. Although it's not uncommon to find them 200k+.

GM pulled a Ford and the atlas bell doesnt share a pattern with the rest of the GM family. However, the AR5 is nothing more than a R150/AX15 so you're manual trans/tcase options are plentiful.

I agree that for the money, there are probably better and more cost effective swap candidates. But I don't normally associate 4 cylinder anything with good torque... I usually think high reving.

I forgot to ask earlier but what is the spline count of the AR5 as well as adapter pattern. Is it 23 spline like Dodge/Toyota or 27 typical of GM? Is it six bolt like most full size trucks or does it go the route of five bolt?

 

[u2slow]

Between the cubes and VVT on that 4cyl... can prob have both good low torque and rev.

I can't go with 6BT... too big and too costly. I love the I pulled this 500k mile 6BT out and I want $5k for a long block ads

Ford 300 then. EFI in the OBS trucks.

Cummins tax is pretty fickle. Up until about 5 years ago I regularly picked up rotten or broken D250s (cummins runners) for a song. Then you get the whole load of swap parts with your engine also.

 

[06h3]

So I had the 3.5L in my H3. I blew a giant hole in mine... I was driving to KOH and all of a sudden all the oil ejected itself from the motor. We dont know where, or why, or how. By the time I pulled over it was too late. I then had a buddy grab 6 quarts of oil at a local parts store. We filled it back up. It never leaked again but the damage was done. It was knocking. I had it towed to KOH, wheeled it sounding like a diesel for 3-4 days....drove it about 20 miles on the highway and parts scattered. We knew it was gonna happen but we still don’t know where the oil escaped from.

I also had issues with the head. The 3.5L had head issues.

With all that said, when they came out with the 3.7L they seemed to have fixed the head problems, the coil pack issues (they just seemed to go bad frequently) and all the little oddities the 3.5L had.

The 3.7L has more power and seems more reliable from the Hummer forums. I’d go that route if you are picking between the 3.5L and 3.7L.

I’ll also mention that quite a few tried to put boost into the 3.5L and 3.7L with no luck. They usually broke parts.

I’d check out this 4200 performance Facebook page. It seems a lot of guys are boosting them and building them. What I don’t understand is that the 5 cyl and the 6 cyl are basically identical minus 1 cylinder. The 6 cylinder doesn’t mind the boost but the 5 cyl does? Kind of odd but I haven’t gone deep into the mods the 4200 guys are doing.

 

[Bebop]

I know Holdener mentions it in his videos, but I'd look for the later engines with 58x/4x sensors. This puts them more consistent with Gen4 LS motors and likely opens up more options for fuel injection.

Terminator X for cheap ECU goodness

 

[IowaOffRoad]

I know this is a GM page, but I have 2 suggestions if you want lightweight and reliable:

4.3L Vortec-obvious choice for size, weight, and power in any rig, bonus if it's a GM
5.0L Ford-more power than above, not much more weight or size. Obviously not the choice for a GM vehicle, unless you wanted to

Obscure choice, and shares GM lineage: Rover V8 pre-Ford ownership. Based on Buick 215 V8, ditch the Rover electronics and go Holley or some other standalone. Or adapt LS injection system for factory parts.

I too have been intrigued by the GM modular inline engines, but too many downsides IMO. I did think that a Trailblazer chassis with engine/trans/axles would be the setup for a reliable chassis swap under a '48-'52 Chevy truck instead of putting a S10 chassis/driveline under them. Bonus points for straight-6 like GM intended!

If you build one up, make a thread here! I'd like to see it, might change my mind.

 

[Lil'John]

IowaOffRoad
I've got a 4.3L sitting in a non-op 2000 S10 in the yard... with only ~170k miles on it. It has crossed my mind to use it and not screw around.

But as mentioned, the I5 specifically seems intriguing except I can't find a weight on it. I did find a weight on the LL8(4200) of ~400lbs.

For comparison, the 4.3L is ~375lbs. It puts out ~180-190hp and ~240ft-lbs.

You mentioned downsides... would you share what you think they are? So far, we have a first hand comment about blowing one up but with unknown root cause. I'm curious if there are any known "bad" issues like the Chevy 3.6L(LTT and LFX) that had issues with the crank case breathing system.

 

[IowaOffRoad]

I was around when they first came out, many oil-starvation crank failures, head gasket failures, cracked heads, water pump failures, timing set failures. I can think of a half dozen examples with less than 100k on them. As some of these were friends with young families that couldn't afford to fix them, it really suck with me. BTW, most of these issues were with the 4.2L. Admittedly, many of the oil issue I think were due to improper oil and oil change intervals. Many of the oil change shops took a while to transition from 10w-30 for everything, as well as some of the dealers. That, coupled with GM's new longer drain intervals with the improper oil took a toll. The ones I know that are still kicking though have 200k+ on them, but they've all had a water pump at least once if not twice.

The 5cyl had some of the same issues in the Colorado, just not as bad/frequent. I don't know much about the updated 3.7L, I'm sure it's better. If I were to go to the trouble, I think that's the one I'd pick.

I hate to bag on them, but I do think many fell victim to corporate hype, dealers/mechanics/customers not heeding manufacturers recommendations, and it not being quite as good of an engine as it could have been due to a couple of minor design compromises. Basically the same issues everyone had with the Chrysler 4.7L V8, which suffered many of the same reputational issues, some deserved, some not.

Finding a good used one is key, get a donor that was a snowbird's vehicle or an octogenarian that took it to the dealer every 2000 miles for service because 'that's what dad told me to do in 1960 (BTW, this is my 68yo mother)

 

[arse_sidewards]

It's an attractive platform on paper but if you want to leave it stock there are other ways to get that kinda power and if you don't there are other things that are cheaper/easier/more supported to build. Unless you just want to be different I don't see the value.

 

[Bebop]

Obscure choice, and shares GM lineage: Rover V8 pre-Ford ownership. Based on Buick 215 V8, ditch the Rover electronics and go Holley or some other standalone. Or adapt LS injection system for factory parts.

Very common in Europe.
Massive POS.

You should look into the Audi and BMW V8s

 

[IowaOffRoad]

Very common in Europe.
Massive POS.

You should look into the Audi and BMW V8s

Well, it was based on a GM design, so…

I’m probably wrong, but many of the design deficiencies can be corrected, and if you are just looking for stock power in a lightweight package it shouldn’t take much to make it reliable.

 

[Lil'John]

Thank you IowaOffRoad Your experience sounds like my small sample size with Chevy 2.8L engines around 86; three for three with them blowing up around 115k miles

In theory, the water pump and oil pump issues should be common with the whole family of engines. But as you note, a lot of the issues you comment on could be related to bad choice of oil.

It's an attractive platform on paper but if you want to leave it stock there are other ways to get that kinda power and if you don't there are other things that are cheaper/easier/more supported to build. Unless you just want to be different I don't see the value.

It isn't strictly the power that is interesting... it is a combination of packaging and weight for the power with a flatish power curve.

I'm not worried about completely stock... I'm also not looking at full drag racing forged everything with aftermarket block.

I agree that there are better choices for either stock power or "max" power. Looking at this is somewhat about being different.

 

[arse_sidewards]

It isn't strictly the power that is interesting... it is a combination of packaging and weight for the power with a flatish power curve.

A 4cyl that has decent aftermarket support and a turbocharger get you the same power curve with similiar packaging, similiar (or maybe lesser) expense and less time spent figuring things out.

 

[Lil'John]

A 4cyl that has decent aftermarket support and a turbocharger get you the same power curve with similiar packaging, similiar (or maybe lesser) expense and less time spent figuring things out.

But now you are talking not stock vs stock.

My experience with two turbo'd 4cyl was they ended up completely gutless at idle. One was a manual and one was an auto in similar cars(same model, different gens)

The main goal of this thread is to gather info about this series of engines and not any particular project target. But to put a target to a bench build; 1975 FJ40 for light recreational wheeling(33-35" tires).
My target goal is a bit over 200hp/ft-lbs. I've had a bit under that in one with a 5.0L TBI and found it to be reasonable to drive.
I think a 4cyl is going to be too short and light for this application. I think it would have to be placed well behind the axle. Plus, I don't think trying a 4 cyl is going to be happy trying to haul around 3k++ of fat FJ40.

 

[arse_sidewards]

But now you are talking not stock vs stock.

It's not like you were going drop an entire Tahoe worth or harness and modules into your FJ.

Many of those 4bangers have turbo applications.

You're gonna need a custom ECU no matter what you.

I don't think trying a 4 cyl is going to be happy trying to haul around 3k++ of fat FJ40.

Look at what some modern crossovers weigh

 

[Lil'John]

To keep on the Atlas tech, here is a 4200 video that popped up:

You're gonna need a custom ECU no matter what you.

What custom ECU? HP tuner, flash out VATS/rear cat error, done. No big deal and more time spent flashing than computer work(3-4 mins tops)

 

[arse_sidewards]

What custom ECU? HP tuner, flash out VATS/rear cat error, done. No big deal and more time spent flashing than computer work(3-4 mins tops)

I meant custom tune. Plugging the ECU into the laptop is 90% of the work. It's not really any more work to download somebody else's conservative turbo tune.

 

[u2slow]

I've got a 4.3L sitting in a non-op 2000 S10 in the yard... with only ~170k miles on it. It has crossed my mind to use it and not screw around.

But as mentioned, the I5 specifically seems intriguing except I can't find a weight on it. I did find a weight on the LL8(4200) of ~400lbs.

For comparison, the 4.3L is ~375lbs. It puts out ~180-190hp and ~240ft-lbs.

The 1993 L35 version (CPI) was rated at 200hp/260ft#. I have it on good account that you can make more power with the 96+ style.

I've not had major problems with the 4.3L. The valve guides like to pass oil after enough miles, and regular oil changing seems to keep their bottom ends happy.

 

[TRINDU]

But to put a target to a bench build; 1975 FJ40 for light recreational wheeling(33-35" tires).
My target goal is a bit over 200hp/ft-lbs. I've had a bit under that in one with a 5.0L TBI and found it to be reasonable to drive.
I think a 4cyl is going to be too short and light for this application. I think it would have to be placed well behind the axle. Plus, I don't think trying a 4 cyl is going to be happy trying to haul around 3k++ of fat FJ40.

Unless you have some goal of making a 'light' or unique FJ40... I believe a 4200/ax15/d300 would be a sweet driving combo. Especially with a mail order tune. You'll have the 200ft lb goal off idle on up.

 

[Lil'John]

The 1993 L35 version (CPI) was rated at 200hp/260ft#. I have it on good account that you can make more power with the 96+ style.

I've not had major problems with the 4.3L. The valve guides like to pass oil after enough miles, and regular oil changing seems to keep their bottom ends happy.

The 4.3L of 96 has it's own set of issues like the spider injector leaking fuel and the two part intake leaking coolant.

Unless you have some goal of making a 'light' or unique FJ40... I believe a 4200/ax15/d300 would be a sweet driving combo. Especially with a mail order tune. You'll have the 200ft lb goal off idle on up.

Light and FJ40 doesn't quite mix. If I were trying for ultra light "fun" rig, I'd do an aluminum based CJ-2/3 with a turbo/super charged i4 and OD.

I'm looking at something unique.

 

[u2slow]

The 4.3L of 96 has it's own set of issues like the spider injector leaking fuel and the two part intake leaking coolant.

A quick googling says there's an updated spider, and updated intake gaskets.