2000 K2500 8.1 Swap

[00CrewCab]

00CrewCab, the factory horsepower ratings wouldn't explain the dramatic differences
in performance that you have observed. Possibly the disparity is because the factory
ratings are based on healthy examples? Check this out:

* '96-'00 L29 7.4L (454) = 290HP / 410 ft-lbs torque

* '01-'03 L18 8.1L (496) = 340HP / 455 ft-lbs torque
* '04-'06 L18 8.1L (496) = 320HP / 420 ft-lbs torque

(Source: dieselhub.com article LINK)

Who knows? You may have been unfortunate enough to have driven not 1 but 2
wounded warriors? My '99 C2500 is no lightweight, but it pulls hard on the onramp,
and effortlessly continues towards triple digits. In English, the drivetrain seems to
have much more headroom than my wallet does. :0)

FWIW I've also driven a 305ci/5-spd GMT400, and it was a night & day difference.
The 305 felt like I was always driving uphill, whereas the 454 feels like I'm always
driving downhill. The difference is not subtle.

Don't get me wrong, I'm not try to call you out at all. Given the numbers above, if you
were used to a happy 454 punching out it's rated 410 ft-lbs of torque, and then managed
to swap in a '04 8.1 putting out it's rated 420 ft-lbs of torque, I don't think the difference
(stock) would be all that much to write home about. Sure, it would be great engine bay
eye candy at the local show & shine, but the 'back dyno' (ie: how far you get pushed into
the seat at WOT) might be in for a disappointment. (Especially if you were to also use
the Allison? Possibly moving from the 4L80-E to Allison accounts for the net loss in HP
& torque between the '01-'03 vs '04-'06 offerings? The Allison is made for long lasting
with severe service, and my understanding is that is takes more HP to run the
transmission itself?)

****

If it helps any to understand where I'm coming from, I started messing with BBCs ever since
a buddy bought a worn out 6 year old '73 Camper Special with a 454/Turbo 400/4:11 and
we rebuilt it to pull harder than new: (Misspent Youth)

To summarize, I'm not trying to talk you out of this at all. Actually, if the 8.1L engine was
the proverbial flagpole on a freezing day, I'd be the one to triple dog dare you to see if your
tongue would get stuck to it. :0)

Seriously, if you go for the 8.1 make sure to pick & choose carefully so that you will have no
fear of an old mild-mannered white-haired dude showing up in dark blue truck and keeping up
with you...or at the very least making it a 'too close for comfort' race at the local drag strip.

Do your homework & make me afraid to drive in Kansas. This would make for a terrific build
thread for all to enjoy & learn from!

No doubt in any of the information you listed, as both my 454’s had well over 200k miles, and one of which was used to haul rock for 90% of its life, VERY possible I had very worn out engines. My original plan was to pull the 454 and rebuild it, but prices for a good Gen6 short block are through the roof near me, and I picked up a 05 8.1 for $500 from a buddy who wrecked his truck. It seemed to be destiny from there lol. But I’ve always had issues with late 90’s gm engines, especially when they get over 200k mi, but that is to be expected of course, especially when it’s used. But this swap is also aimed at the fun factor, and to test my own abilities as a mechanic, and automotive research. It’ll probably be about a year before this swap will even be close to done, mainly because I’m aiming for as oem as possible, not that I can’t fabricate or rewire my harness, I’d just prefer to find a plug and play system, especially considering it is oem in this platform. I’ve got to ride in a very healthy 454 a couple time, and I will agree, it was a breeze with anything we hooked to it, which is actually what made me choose a 454 when looking for my own gmt400 truck. But I’ve never had a new engine in any vehicle, all used, all higher mileage, so my own opinions/experiences are totally blown away by factory specs.

 

[L31MaxExpress]

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[L31MaxExpress]

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[Road Trip]

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Shortly after that truck followed me home, I watched this exact video and got a real
bad case of 8.1L fever. I thought that I had come to my senses (in that I already have
more than I can justify needing in the driveway) ...but now thanks to you & Mr. Holdener
I might start once again looking for an especially crispy/rusty yet complete 8.1L donor truck?

****

So here's my dilemma. If I stick with my normal approach, I will waste no money yet run
the risk of leaving behind no performance legacy in a hobby I've enjoyed all of my adult life?

Or do I think about piecing together a '99 RCLB Clark Kent/super sleeper version of one of my all-time favorite
vehicles? -- Witness the Farmtruck:

You must be registered for see images attach

(Great soundtrack. Go HERE and start at ~2:13 to get right down to business.)

****

This has been an interesting & enjoyable bench-racing session this evening.
And I know that old guys are supposed to check out quietly & with dignity.

But it sure would be fun to take an old chore truck and surprise a few folks
at the dragstrip. Heck, I just got made a grandfather a second time...my
twin daughters each had a baby boy. So, if I ended up being the cool
granddad that made the most noise of them all, then this would leave
a lasting impression on them? Which, in my mind, would be a huge win
in the legacy department?

Tempting... :0)

 

[CumminsFever]

I'm a huge fan of the weird or "different" modifications to trucks. I fully support an 8.1 swap into a gmt400.
I'm an even bigger fan of rides like "farm truck". Been watching them for years!
I've done quite a few engine swaps into these gmt400 trucks, however, it's been all diesel stuff. I kinda just "dive in". Get donor engine, yank truck's original engine, and fab whatever is necessay to stuff the donor engine into the truck.
OP- don't give up on your 8.1 swap vision. You may not come out dollars ahead of just rebuilding a 454, but you'll have something unique that YOU did. You can't buy that feeling. You can't buy that smile. You build it!
Do the swap and enjoy! Chase that "farm truck" dream!

 

[b454rat]

Semi local yard to me had a couple dozen medium duty trucks with the 8.1/Allison. I need to go there again, they seem to get more "cool" stuff than some other yards. But the motors ain't cheap. Can't remember last time priced one, but since it will be 100% complete might not be bad. Saw one on marketplace for like $500.....

 

[someotherguy]

While we're spending other people's money.. Hell why not go nuts and look for a bus that has the PSI 8.8L in it.. 265hp/548tq

You must be registered for see images attach

Make some custom "535" crossflag emblems for the fenders and leave 'em wondering WTH?

Richard

 

[b454rat]

Now Im looking into these engines again. Local-ish yard still has 5-6 of em. They are out of medium duty trucks, which IIRC is better than the trucks since it has the A/C mounts where stock would be, where as trucks puts it down on the frame, and don't fit our trucks.

 

[HotWheelsBurban]

While we're spending other people's money.. Hell why not go nuts and look for a bus that has the PSI 8.8L in it.. 265hp/548tq

You must be registered for see images attach

Make some custom "535" crossflag emblems for the fenders and leave 'em wondering WTH?

Richard

OMG...and that's just the serpentine belts drive setup!
It'd be a beast though....

 

[Road Trip]

Now Im looking into these engines again. Local-ish yard still has 5-6 of em. They are out of medium duty trucks, which IIRC is better than the trucks since it has the A/C mounts where stock would be, where as trucks puts it down on the frame, and don't fit our trucks.

b454rat,

You are correct re: advantageous 8.1 G-van & Medium Duty A/C compressor location
vs. what the 8.1 2500 Silverado/Sierra setup has. When I was suffering from the 8.1 upgrade
fever I found a couple of clear (GM release?) photos showing the differences in the 2 serpentine
setups. (For those reading along but unfamiliar with the compressor location issue, see attached.)

...Also I’ve already picked up my donor engine, it’s a 2006 8.1, from a 3500 pickup, ran great but was my buddies truck he wrecked.

...Any input or clarification is greatly appreciated, and thanks for everything so far.

00CC, good to hear that you have the 8.1 upgrade in your possession. And also that you have
access to the history of the way this engine ran prior to being sidelined. (As opposed to buying
an engine out of the treasure yard with little/no clue on it's prior performance history. I always
consider those a 'potential rebuildable' -- ie: I have to assume that *everything* is suspect/bad
until proven good.)

By contrast, you buying your buddy's engine allows you to take the opposite perspective -- everything's
good until proven otherwise. :0)

Speaking of 8.1 upgrades, last year I really scoured the interwebs for info on this powerplant, and since you seem
to be serious about heading down this path, here's the best rabbit hole I found for myself for all things that the
8.1/build/swap crowd would be interested in: (garage.grumpysperformance.com: "8100 chevy vortec engine swap info" )

****

As for this forum, there's a lot of hard-won knowledge and hands-on experience in here.
In order to get the right talent interested, they really want/need to see clear pics of the
vehicle, the engine bay, the upgrade engine, etc. (Look through any of the build threads
to get an idea of what seems to work best.) Consider uploading a pic or 2 in the
Member's Area/Introduction forum, along with a little background on yourself. And go
ahead & start a Build Thread for your vehicle. Remember, all I can see from over here
in upstate NY is whatever you put on the screen for me.

But between the 8.1 rabbit hole + fellow GMT400 enthusiasts in here + your coworkers
at the dealership, you should have the critical mass necessary to pull this off.

Make it so!