jimmy p's H3 Build

[jimmy p]

A couple years ago I began to get the off-roading itch again and wanted to build a rig that I could take the family out with. A Jeep was a logical choice with plenty available on the used market as well as unlimited aftermarket bolt on parts but I am a GM guy at heart and enjoy building/fabricating as much as actually driving. Within the GM lineup I settled on the H3 based on a good platform naturally for offroading with approach/departure and available 4:1 tcase, small enough for trails but large enough for the family.
I knew I would eventually be doing a solid axle swap and V8 swap so I was already shopping for those parts. I wanted something that I wouldn’t be afraid to scratch up on the trails so I was originally shopping the cheapest H3s on craigslist and copart when I came across one on the for sale section on this forum from user 5gn-h3t which already had a recently completed SAS and SOA done for a price I couldn’t pass up. I borrowed a truck from work and rented a trailer and made a 16 hour round trip to pick it up in Pennsylvania. It turned out to be a great stating point with all of the heavy lifting already done.


I got it to fit in the garage with the roof rack removed, just scrapes the roof which means it wont be getting any taller

I got lucky and came across an totaled 06 yellow adventure package so I pulled the rear locker and 4:1 t case out and parted out the rest of it to fund the rest of the modifications


during the first week of covid lockdown I took the family out for a quick spin to the carwash and heard a loud pop from the front end. Turned out to be a outer front axle. Turns out the axle already had chrome moly shafts and joints in it, but whatever vehicle it had come from must have had some power because the other axle shaft was also already twisted. I replace both, thanks to some help from the previous owner and 4speedfunk for parts/advice.

Then came the 4th tow hook and "lightened" rear bumper. I sectioned the spare tire carrier to tighten it up against the back door so it didnt look like it was hanging off the back so far. I also added a H2 spare tire license plate holder to relocate the plate. I added a rear view mirror/backup camera.

 

[jimmy p]

Mounds offroad park, stayed out of the mud until the very end and then it involved 20 minutes of wheel spinning to get out. Took days to clean

Drummond Island

Oem locker install

Front skidplate and another steering box leak

Rock sliders

Tcase inspection, cleaning and replacing plastic shift arm

Silver lake sand dunes

Tcase skid

 

[jimmy p]

I had several xterra steering box leaks and a ps pump failure as well as looking for an opportunity to alleviate some steering effort so i upgraded to a hydraulic assist. PSC ram and mounts with universal hoses and fittings to the now tapped and fully rebuilt xterra box.

Also here it is testing all the new steering gear at a new local park, holly oaks. Led lights added upfront with cheap amber housings in the oem offroad light grill
2

Added some switches for the lights and locker. I like oem style switches and these ford upfitter switches fit the bill. They route to an aftermarket relay/fuse box under the hood.

 

[MilamJR]

Might need to air down to get it back in the garage.


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[jimmy p]

Engine swap is next and I will probably need some help from those of you that have done it already. I picked up a dropout ls2/4l70 from a 2007 trailblazer ss.

Installed an h3 alpha oil pan, pickup, windage tray, dipstick and dipstick tube.


Induction will be tbss maf and rubber elbow mated to a full-size truck airbox

Mounts will likely be fabricated to use the factory tbss engine side mounts. I may also do something more along the lines of the current performance with builder bushings but like the idea of the softer oem mounts if possible.

Wiring.....jamie is busy until summer and no response from current performance yet so I will likely be doing it myself. I am about 80% there with the wiring diagrams and pinouts but haven't physically started splicing yet. I am hoping to keep it plug and play into the factory harness with some jumper harnesses between them.

Calibration. I would like to maintain the factory e67 ls2 tbss base calibration instead of any kind of custom chassis dyno tune over an base 5.3 alpha specific calibration. Challenges with this so far are the differences in cruise control and traction control between the tbss and h3 vehicle architecture. Also may impact some 4wd low calibrations that are unique to hummer.

Trans..would like to keep the 4l70 and trying to figure out if i can dent the pan near the driveshaft (i have more clearance than stock due to the sas) or exactly what I need to replace in the bottom end to run the h3 specific pan.

Exhaust will be alpha manifolds, tbss converters, custom 2.5" dual back to some dual mode zl1 camaro mufflers wired for quiet/loud modes


Front acc drive, starter and ac will probably stay tbss. Not sure if i will spring the cash for factory alpha hoses and lines or just go custom.

Fans...if i can find a good deal on an alpha fan, clutch and shroud i will go that route but more than likely will try ls1 electric fans.

Came across a cheap used snorkle, not sure i am going to use it but I have it just in case

 

[Jeff V.]

This is gonna sound funny, but did you get that snorkel from a guy in Washington Township?

 

[jimmy p]

This is gonna sound funny, but did you get that snorkel from a guy in Washington Township?

Yeah that was the one, sounds like i got it just in time! Small world indeed. I'll let you know if I decide not to use it.

 

[Alpha X]

Cool build, I like it.

 

[amrg]

Dont bother with LS1 fans. Either stick to the clutch fan (way superior to everything) or if you're set on electric just get the ctsv/zl1 electric fan. 850 watts brushless fan equivelant to 1200 watt conventional fan, soft start, no relays, speed can vary from 10% to 100%, fits perfectly the oem radiator, 19" blade covers the entire rad core, Works easily with the e67 pcm and nothing is superior to it, nothing.
Make sure you have the alpha alternator with 145 amps too to run it, at full power it pulls almost 70 amps continous

 

[jimmy p]

Dont bother with LS1 fans. Either stick to the clutch fan (way superior to everything) or if you're set on electric just get the ctsv/zl1 electric fan. 850 watts brushless fan equivelant to 1200 watt conventional fan, soft start, no relays, speed can vary from 10% to 100%, fits perfectly the oem radiator, 19" blade covers the entire rad core, Works easily with the e67 pcm and nothing is superior to it, nothing.
Make sure you have the alpha alternator with 145 amps too to run it, at full power it pulls almost 70 amps continous

The alpha specific clutch, fan and shrouds are too expensive new if i can even find them. I am not sure what makes them unique or if i can grab a junkyard fullsize truck fan or use the tbss fan which is huge. I think 06 h3 said it stuck out too far when he did his swap. I can fab up a shroud if needed. Also the tbss has an electronically controlled mechanical fan, not sure if there is an advantage but it is already wired and programmed in.

As far as electric goes, it has been 10 years since I have done a conversion like this so I shouldn't be surprised that a better fan setup has come out since the ls1 fans. What gen zl1/v are you referring to? Coincidentally I was looking at a set of 2013 zl1 fans on ebay. Thanks!

 

[amrg]

The fan will be made by spal, the tag will have 850HT listed (indicating 850 watts).
The tbss uses an electro viscous (EV) clutch fan. I dont know why GM did that, but my assumption would be that GM needs to control the fan when ac is needed, and since an electric fan wont cut it cooling wise on the small tbss radiator, they went with a superior clutch fan that can be engaged electronically.
But anyway, the same wire used to control the clutch would be used to trigger an electric fan on/off or be the signal line for the ctsv/zl1 fan. I havent looked at a tbss tune, but the ecu has tables for fan request % vs ect & ac pressure, those will need to be checked and the fan type changed from EV to discrete (for on/off signal) or pwm (for the ctsv fan).

The last picture would be the fan superimposed on the radiator

 

[Gpcalero]

The alpha specific clutch, fan and shrouds are too expensive new if i can even find them. I am not sure what makes them unique or if i can grab a junkyard fullsize truck fan or use the tbss fan which is huge. I think 06 h3 said it stuck out too far when he did his swap. I can fab up a shroud if needed. Also the tbss has an electronically controlled mechanical fan, not sure if there is an advantage but it is already wired and programmed in.

As far as electric goes, it has been 10 years since I have done a conversion like this so I shouldn't be surprised that a better fan setup has come out since the ls1 fans. What gen zl1/v are you referring to? Coincidentally I was looking at a set of 2013 zl1 fans on ebay. Thanks!

I threw away my clutch fan and shroud set up. No idea they were worth anything, I figured they were junk lol.

 

[06 H3]

I ended up running a factory fan and shroud from an alpha

 

[jimmy p]

I made a mold of the tbss 4l70e trans pan to check clearance to the h3 driveshaft. It was close but I decided to play it safe and clearance as much as I could from the stock pan without modifying the internals. I ended up running the h3 specific filter but otherwise stock 4l70e parts. Still crossing my fingers it won't have any clearance issues but it will be hard to tell for sure until I get it all installed.

 

[jimmy p]

After some sketchy moments the old engine and trans are out. I need to fix some odd rust spots on the inside of the frame and clean up some welds before installing the new powertrain.

Manifolds, hptuners, h3 fan, cooling hoses, fluids are all in the mail.

I broke down and ordered the current performance mounts and tb pedal bracket to save time on making my own.

Need to figure out fuel lines, exhaust routing, wiring and a few tune related items

 

[JPaul]

Looking good.

On a side note, you should probably compress your images, they're coming in at 5-6MB a piece which results in really slow loading and if you're using the photo hosting built into the site (which is what it looks like when I inspect the image sources) then Alrock might talk to you about the space usage. It's best to have them at only a few hundred KB instead.

 

[jimmy p]

Looking good.

On a side note, you should probably compress your images, they're coming in at 5-6MB a piece which results in really slow loading and if you're using the photo hosting built into the site (which is what it looks like when I inspect the image sources) then Alrock might talk to you about the space usage. It's best to have them at only a few hundred KB instead.

Thanks I expected the site was compressing them for me but it doesn't look like it .....and that explains why this thread loads at a snail's pace.

 

[jimmy p]

Manifolds, bolts, studs and gaskets came in. I painted them with high temp paint. Engine is in but still fighting with the engine mount alignment.
Also one of the lower h3 alpha oil pan bolt holes do not align with the trailblazer/fullsize truck bellhousing. Reading up on some of the ls conversion forums, many people run without the lower bolts so I might just run with it. Otherwise I have to pull everything back out and swap in a alpha specific bellhousing.

 

[jimmy p]

Alpha fan and clutch came in. Similar diameter as the stock i5 fan. Also shown is the trailblazer fan. Ideally I am going to use the alpha clutch which mounts the fan close to the engine and the larger diameter trailblazer fan.

 

[jimmy p]

A small rust spot in the floor got larger and larger as I tried to find solid metal to patch to. I also fixed two other holes in the frame that I could only access while the engine and trans were out.

 

[JPaul]

Good heck, that is a huge hole. Water had to have been getting in there for quite a while to do that.

As for the trailblazer fan, that is interesting. does it fit in the opening of the Alpha fan shroud? Seems like it'd pull a lot more air with the attached cowling or whatever it's called on the fan blade tips. I know that doing that increases the efficiency of a fan by a fair bit as it stops air from being able to slip over the tips of the blades. If you can get me a measurement of the diameter of that I want to check some clearances. You might end up running into an issue with the air intake, it's a pretty tight clearance stock.

 

[JPaul]

Looking at those pictures of the fans I never realized how much smaller the V8 fan looks compared to the I5 fan. Wonder if they only did that for clearance issues. Get me the diameter of the stock Alpha fan and the Trailblazer fan and I will verify clearances.

 

[amrg]

The intake tubing comes in the way on the alpha. I found out the hard way when trying to put a mechanical fan on a car intake for my LS, no way its happening (car intake sits a few inches down)

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[jimmy p]

I don't have an oem alpha fan shroud to verify but I doubt the trailblazer fan would fit in it even on the alpha clutch. It seems to still clear the tbss induction tube and radiator cap but just barely. If I have to move the engine forward a little it might not work. I also haven't verified if the trans cooler lines will clear on the bottom. Lower radiator hose is close.

 

[jimmy p]

After two days of struggling I haven't been able to get the current performance mounts to line up. I emailed them and they said they have only seen this a few times in the past 10 years. I am guessing my frame rails might be tweaked from the sas and missing cross members. There isn't a way to get up in there to slot the holes when the engine is installed so it will be coming back out. This will give me an opportunity to update to the alpha bellhousing so that is on order (I was pleasantly surprised to see it was only $67 new). Also the exhaust manifolds contact
the factory engine mounts so i can trim those up and clean them up too with the engine out of the way. One step forward, two steps back.