Can't blame you for wanting to go V8, but I'm surprised by the bad luck you've had with the 5-cyl. The Atlas engine is a very high-tech DOHC little engine. Mine has been reliable as heck. I've seen quite a few used H3's with real high mileage listed on fb and craigslist. The 06's unfortunately were weaker, but the 3.7 seems just fine to me for daily use, and the trail use I've done.
The only way I'd put a rebuilt I-5 in mine is if I rebuilt it myself. Too many of these rebuilders cut corners or their guys overlook the simplist of details (don't get me started!!). And there's no way a customer knows what has and hasn't been done. A buddy of mine juuust went through that with a rebuilt Audi engine he bought from a 'supposed' major rebilder (the engine-master's guy). He was going to re-do his and thought, "Welllll, maybe an Audi is best left to that rebuilder." What a crock. There were so many problems he had to remove the engine and re-do a lot of things on it because the oil pressure was low. A lot of things doesn't look like they replaced. He's have been better off with what he had! Thats probably what happened in your case. This same guy competes at Engine Masters every year (Ford V8's) is very intrigued by the Atlas engines (and he's a Ford guy!). He's looked them over pretty well, says there's probably waayy untapped power in one of them with the right mods. Which might be another option for you to consider as a cheaper power upgrade. Then you don't have the weight penalty of a V8 either.
I wonder how easy it is to put a I-6 atlas in a H3 (from like a Blazer, pickup)?
That said, you can't beat a V8. Lot of these smaller engine cars that advertise high HP, you have to wait till the transmission downshifts 3x and the engine spools up to 5,500 RPM to get your power. They still feel 'doggy' in many cases. We have a Jeep G/C with the high-output 4.7 in it. It's lighter than the H3. It moves the Jeep around effortlessly. You blip the throttle and it snaps yer head back some. It's my kid's car now. When she was learning to drive, she'd come home and talk about the gutless Driver's Education cars and how going up a hill she'd put the pedal to the floor and it wouldn't go. She once said to the instructor, "There's something wrong with this car, it just won't hardly go up the hill." ha ha. She was used to her Jeep passing anything on the road and not having to down-shift to do so! Kind of a funny story there.
Good luck on your build. Can't wait to see how it goes.
Totally agree with you about i5s Atlas engine!
Its an amazing and super reliable engine itself (if well take care of it of course, that equals to periodically cleaning throttle body, iridium spark plugs, clean maf sensor and change Oil with good synthetic using UPF-61R oil filter and good air filters aswell).
And what your buddy suspects...is a total reality! The 3.5 and 3.7 hidden a lot of power that is reduced from factory....especially the 3.7 (its a 3.5 with more bore and lot of head work, better flow head and valves)
With proper mods, I achieve my
previous 3.5 automatic, to do the 0 to 60 mph in 9.3 seconds. That is using 285 75 R16 ko2 tyres (33 inch). With the next mods: Volant cai, muffler deleted, Orion headers (best by far), Supermodulation ported throttle body+supersparkz, Iridium acdelco plugs, EFAN conversion, 5w30 synthetic oil, and of course an amazing PCM of NC that they revised multiples times with datalogs to achieve the best.
A friend here have a 2008 Hummer
H3 3.7 auto with 285 75 R16 ko2 too, achieves 0 to 60 mph in 8.9 seconds...that is with same mods than mine,
except Headers, efan conversion, and Airdoc intake (not volant, but I prefer Airdoc intake over Volant by far).
That same H3 is soon going to receive a set of Orion Headers, efan and Pcm retune by pcm of Nc...and we are
expecting to achieve close to 8.2 seconds from 0 to 60 mph, power close to 290 hp (with headers and efan).
Now I have a
2008 Hummer H3 alpha with 305 70 R16 Toyo MTs, that I already refurbish and tuned.
I achieved a 7.7 seconds in 0 to 60 mph, that is with: JBA shorty headers, front cats gutted and rear cats replaced with highflow metallic ones, muffler deleted, EFAN conversion, iridium spark plugs, JET performance throttle body, AFE PRO Dry S filter and another amazing Pcm of Nc Tune that they revised another 4 or 5 times for me to achieve the best from tranny and engine.
That acceleration is without intake, I am going to put an Airdoc and do another retune, and maybe I reach 7.5 seconds or lower of acceleration from this beast.
Conclussion: Alpha is amazing in stock form compared to a i5 3.7, but after putting bolt on mods on both, the 3.7 is way closer than you might think to a bolt on 5.3 v8. Of course...there is no replacement for displacement, and power is not torque. 5.3 v8 brights there, and towing...amazing the difference.
Hope my experience helps here! From Spain with love
