Hey guys,

I have a quick question for you,

What all would be needed to swap out a broken non vortech 350 out of a 95 Hummer H1 in favor for a 496 ci (8.1L) vortec motor out of a newer 2500/3500 truck.


Thansk
Shawn

 

if you have time and money anything is possible....

motor
motor mounts
all wiring from a 2500/3500
allison or 4L80 tranns (or that big 6 speed Z something or another dont remember the model #)

without looking i would say it would be a total custom setup... but it is possible...

 

Good news is you have LOTS of room in that H1 to play with. Don't know if an ally would clear the tunnel but you could get a 4l85e somewhere cheaper anyways.

 

I think they come with a Th400 in the early years, 91-93 then 94+ have the 4L80E. The final years have a dmax allison but they are about still about $130K used which is crazy.

Ive seen a few 6.0L or 8100 on e bay with the wireing harness, so i would think it should just "sorta" simple.

 

I've never seen a gas-powered Hummer. With a 350 L05 that thing must be a dog.

I might suggest you install a Vortec 454 instead for a few reasons. First of all, you've already got a 4L80-E in there and you'll need the right wiring harness to control the engine and the transmission. With an 8.1 that limits you to finding a 2500 BigBlock Suburban, Yukon, or Avalanche harness. Also, the Mark VII bigblock is a strange thing. It has symetrical intake ports unlike every other big block, and that allows for the two extra "missing" headbolt holes. So, the heads are of course proprietary, as-is the intake manifold. There's no distributor, the 8.1 has a coil per plug like the Gen-III/IV smallblock, so the valve covers can't easily be swapped out for others without taking that into consideration. The 8.1 water pump is also specific, so aftermarket stuff doesn't work here either. Mark-VII heads have a totally different cooling arrangement - water actually exits the ends of the heads and the intake manifold has nothing to do with it. The 8.1 also has a weird firing order, so no regular roller bigblock cams work in it.
With a Vortec 454 you get a Mark-VI bigblock that an entire world of aftermarket heads, rotating assemblies, valvetrain, and all kinds of other parts are readily available for. All Mark-VI bigblocks are 4-bolt mains, so every production L29 Vortec 454 is 4-bolt. These have one-piece seal cranks and accept heads from other generation big blocks.
Every production Vortec 454 (1996-2000) with an automatic came with a 4L80-E or a 4L80-EHD, so about the only thing you'll have to pay attention to with the wiring harness is 4WD or 2WD.
I think a 454 would be easier and a better platform for modifications. Just my opinion. I've got one and am definately a fan of the L29.

 

Good greef James, Your a walking 8.1 dictionary arent you!

To be honest with you motor wise i dont care, Just seem's intoday times it would be smarter to go with something bigger than rebuild that 350. You all know how slow a truck / tahoe was back in the early 90's... now make that
10,500 lbs!

The H1 is full time 4wd or awd... so i guess a two 2WD harness would work... or i could change the transfercase and so i have 2wd 4hi and 4lo...

Ive seen a few 502 swapped in but they all have a carb.

 

James -
Good explanation on the differences that make the 8.1 so different. Thanks!

 

Honestly, nothing wrong with going 502 carb setup either then unless you really want the EFI pcm to play with.

 

I just dont want a carb, we live in the mountains so the temp can be anywhere from 0 to 90*

Yesterday alone the tempatrue was 60* at 7:30 am, 30* at lunch at 18* last night...

That and i have never had any good luck with 4 wheel a carb.


So if the ticket is a 454 motor where is the best place to start looking for it.

 

8.1 is easy, I have done it