1st ever big block GMT900? (frankenburban 2.0)

Part 1: Introduction

Some of you may remember my last Frankenburban 1.0, served a very good 5 years then I got tired of working on the constant stupid failures, I wanted to go racing not wrenching on the tow vehicle so I upgraded to a 2008 suburban HD with 54k miles on it. Thinking this would have been the smart choice.

cloth, "bench" seats with a 6 speed 4wd? LS V8? that sounds like a hell of a time, big power jump from the old suburban too.

Cruise control, air conditioning, overdrive, IFS, FM radio + aux in = this thing was a HUGE upgrade in ride quality. Really enjoyed it did some basic maintenance (Brakes, Bilsteins, B....tires!)

Majestic AF... (for a 6500lb truck, no seriously that is how much it weighs I visited the scales one day on my way to work)

It was much less stressful towing with a vehicle 23 years newer and since its an HD the 3/4 ton has all the goodies and coolers and beefer parts like brakes and 8 lug hubs etc, fully boxed in taller frame. Its pretty robust.

Part 2: Fitting the needs

Went up a size in tire with some BFG K02s and it looked good/perform great. Had a lot of planned camping with a truck this summer so I got it ready for that by adding a roof basket upon the factory roof rails/oem cross bars.

I bought a welder not to long ago so I wanted to get some practice and I ended up buying a small roof rack for like subaru or something with a tiny roof, however this is a long wheel base full size truck, it has over a 100" long roof so I decided to extend the acquired roof basket, which was totally fun!

get a little more practice more comfortable and the lift made it easy, its a great tool for many things, like hanging pieces from it with mechanics wire to paint or have a party.

multi useful really, well worth the investment!

Since it was going to be the tow vehicle I was thinking getting the race car to match the truck like the Millen livery tribute:

So I turned it into this!

and then we went to the beach for the weekend

Then until recently I have been hearing a noise.

knock knock...

who's there?

LS

Diag confirmed/isolated to cylinder 5 under load it rattles after the engine is warn, wrist pin or rod knock but doesn't change tone with increased rpm, pretty constant which makes me think more towards wrist pin which is unheard of the incredibly reliable LS v8s.

Seriously I have 3 running and driving rotary cars right now. I will video it if proof is required.

Part 3: Now WTF?

Here is the part where we are as of now, I have only owned the truck for 5 months. I bought this not to make it a project so do I just fix it and live with it or go berkeley it and make it a project? How adult do I want to do this? Pay someone else to pull the engine and replace the cyl 5 pieces and carry on with my day, maybe add a tune at the end of the day?

OR any multitude of LS based Gen IV small block would be an easy swap, custom turbo kit is doo-able. The problem is with the small block is that where it makes its great power, I don't like winding it out to 5000rpm to tow, it just always seemed strained which has led me toward my big block idea since the duraburb is FAR too expensive and cummins swap is outright silly.

Vortec 8110, AKA 496 this is a gen VII big block chevy which is basically a stroked 454 with LS style ignition setups and OEM cylinder head porting style, however the L18 is cast iron heads/block. But you do get 300ft lbs at idle. its just staggering...

compared to the LQ4

I'll have much more pulling power with the 1800-2800 rpm range that I enjoy.

here is the problem though, they stopped offering the L18 in 2006 body style (gen 3 LS) HD trucks (suburban/yukon/avalanche) and it was still offered a few years later for box trucks and etc.

the suburban 3/4 ton chassis ended production in 2013 which was the last of the GMT900 bodystyle. The GMT800/900 HD frames are the same. Since why would they design a new HD chassis for the trucks only to kill it a few years later, this is GM - change comes SLOW and everything is traditionally built off of what is already easy to manufacture.

There are some challenges:

L18 cam/crank setup for gen 3 LS engines

utilize big block accessory drive

multiple options for accy drive

engine mounts?

BUT!! There are some easy parts:

GM offers a crank trigger kit to use the 8.1 on a gen IV LS ecu 58x/4x crank/cam instead of 24x/1x with the crank in the back of the engine it relocates it to the front timing cover like the engine that will come out of the truck.

I can carry over my alternator and PS pump from the LQ4 but use the BB brackets

AC compressor is the exact same part number, maybe just disconnect and re-attach after swap and not open the AC system up (which would be great) and the hoses might be long enough since its even in the same location.

The idea is to run the L18 on the LQ4 computer using all the same sensors the truck won't know the difference. HP tuners is pretty reputable and I am in the detroit area so tuners are easy.

If I buy suburban/avalanche engine mounts for the 8.1 I think it will just bolt up... Kind of a gamble but it may actually work.

6L90E can withstand 900hp reported so no worries there, use the existing torque converter and bolt it up to the big block flexplate (and I am pretty sure the starters are the same too) and the trans bolts right up!

All this seems so logical, so why can't I find on the internet someone who has completed an 8.1 into one of these? I literally have been searching for months and I did a lot of other homework on this powerplant when I was considering putting an L18 into my old suburban. any old BB header will bolt up to these heads too so finding some ceramic coated shorty heads could work great!

So... should I take the plunge? and if I do I think I will toss a cam in it too - might as well go nuts if were this far.

The 8.1 swap would be pretty cool, especially if you could pull it off without significant engine management woes. Please try it.

In theory is should bolt up, maybe need a different fan shroud - but the GM trigger kit is 500 dollars plus the engine I still haven't bought. Found a complete drop out locally with trans and etc from a box truck so it has different accessory drive but its 1 serp belt instead of 2.

truck L18:

box truck L18:

Nice thing is that I can use the existing lower radiator hose and the upper hose doesn't wrap around the front of the engine! I can probably get away with the 6L radiator.

the real trick one would be out of a kodiak!

can you say onboard air? However its much more rare and buying an ARB air compressor would be easier and likely just as expensive if not less...

Pictures on the last comment don't seem to work... could be my work..

Pictures not working for me either, seems awesome though. Free local volunteer here should you need any help!

Was unaware of the torque specs for the big block...still have desire to stuff a LB7 with a ZF six speed man in my '91 chev 1/2 ton ext cab....330hp with 500+ftlbs @1800rpm.

Id do the 8.1 mostly because my experience with the 5.3 is pure dissapointment.

I'm guessing the 8.1 just wouldn't pass tightening emissions standards. Otherwise it would have made a bit more sense as the top (gas) engine choice in something that heavy. Can't wait to see how this turns out.

RossD wrote: Pictures on the last comment don't seem to work... could be my work..

That was my fault, I fixed them now :)

dropstep wrote: Id do the 8.1 mostly because my experience with the 5.3 is pure dissapointment.

That is kind of my impression, the 5.3 felt great in my friends 1/2 ton pickup but with this heavy truck even with the 6 speed the peaky small block engines do not match up well, I was expecting more low end grunt but it pulls like my 85 did with just added creature comforts.

Ran out of time today to look at this:

https://detroit.craigslist.org/okl/pts/6205735735.html

I will try next week, saw one yesterday for cheap (1750 with core) but was missing some parts but did have a 45 day warranty...

4L80E 2WD with tq converter must go for 400-700 I imagine...

so what engine and trans is in the HD Burb now? (maybe I missed it?) 6.0L? Did they put the 5.3 in the HD Burbs?

I'd just get another 6.0 and do all the goodies to it and then drop it in. Lowest cost and least down time, since you were tired of working on the tow rig.

onemanarmy wrote: so what engine and trans is in the HD Burb now? (maybe I missed it?) 6.0L? Did they put the 5.3 in the HD Burbs? I'd just get another 6.0 and do all the goodies to it and then drop it in. Lowest cost and least down time, since you were tired of working on the tow rig.

its a 6L with the 6L90E transmission 4wd

I figure if I have to go through the work of removing the engine from truck something better would go in its place and a low mileage 6.0 can command some decent money.

I still haven't ruled that option out though.

I vote for 8.1

400ft/lb at a tick over 1,000rpm sounds like fun

any state rules on engine swaps - like must be same year or newer than vehicle - emissions testing?

I swapped the 8.1 and Alison back into my 2500hd together and the engine hoist was hating me. I have the old engine sitting here if you have something interesting to trade for it and can use it?

8.1 + cam...

oldtin wrote: any state rules on engine swaps - like must be same year or newer than vehicle - emissions testing?

I think he's in Michigan, so no testing needed.

chandlerGTi wrote: I swapped the 8.1 and Alison back into my 2500hd together and the engine hoist was hating me. I have the old engine sitting here if you have something interesting to trade for it and can use it?

the old 8.1? or 6.0?

And yes no issue with emissions or inspections since I live in Michigan. Next step is to check the service manuals to double check some sensor locations and etc, see if any wires will need extending and such and keep taking a look at various engines.

secretariata wrote: 8.1 + cam...

that would be the idea! Raylar engineering has an RV cam that I think would pair great with this application.

It was an 8.1 originally, the spare is locked up and appears to have been run out of oil.

In reply to chandlerGTi: I may take you up on that, but getting the engine may be tough.

Right now I am looking up some information regarding the sensors see how "plug in play" this can be EFI wise...

the knock sensors different from gen 3 to gen 4 motors My current engine does not seem to have the knock sensors in the valley of the v-8 but rather on opposite sides of the block like the 8.1 but the sensor itself is a different style. But if the threads are different I do not know if I would want to go into try and drill/re-tap situation.

my engine:

big block: but if the threads are the same I could in theory just bolt them onto the block.

The coolant temp sensor looks like I need to go from a 1/2 NPT to 3/8 NPT and then it should swap over fine, slightly different location between the engines but should not be an issue.

The map sensor is the same part# for both engines and then cam/crank will be updated with the GM timing chain kit:

big-Block Crank Trigger Ignition Conversion Kit

• Enables the use of the latest aftermarket electronic control systems (gen IV ECUs)

• 58x reluctor ring for installation on the front of the crankshaft timing gear

• 4x camshaft gear

• New design front cover with camshaft position and crankshaft position sensors

• Double-row timing chain for greater durability, stability and timing accuracy

The 6L throttle body bolts onto the 8.1 intake manifold so I will use that with the 6L fuel injectors because they have a different electrical connector but they are similar part numbers so size/flow may be close but slight part number update due to electrical connection: but this is kind of a guess. Since its a delphi harness maybe just de-pin/re-pin is an easy solution to retain the 8.1 injectors. AC delco part number for 6.0 = 2171621, the part number for the 8.1 = 2171563

anyone have a gen IV 6L repair manual? I can only find gen 3. I have a feeling that I actually don't have an LQ4 but an LY6 but I have never seen any displacement on demand or VVT things associated with it...

IIRC the GM Computer allows you to tune how you respond to knock sensor input. They assume there is "noise" so you can set how much of the input you ignore. It seems like you could bolt them on and tell the computer how to respond.

For the injectors ( from Pirate 4x4 ):

2002 8.1L injector number acdelco = 2171563, 30 lbs/hr @ 43.5 psi, around 40 lbs/hr @ 58 psi.

2005 6.0L injector number acelco = 2171621, 29lbs/hr @ 58 psi.

Gen IV fuel system is around 60psi so eight 29 lb/hr injectors should be good enough for 400 hp.

This should be interesting. The pictures aren't working for me either, just the RX7, but I will be watching this. We have an 06 8.1 GMT800 Sub now, and I like that body style, but I also like the 900. I think if I went through all the work I would probably do the Duramax swap (and I will be doing so on ours in the future), but I totally understand that there is a difference in purchase price and maintenance price between the gasser and diesels. Too bad it wasn't timed right or I would sell you the 8.1 and 4L80 from ours. Just can't do the swap until we are done with the second mortgage aka daycare.

Love this build! I vote big block. I'm not a huge fan of the 6.slow in any application (try driving it in a 3500HD dually...painful).

I don't know of any completed examples of this swap, but Fred from Dirt Everyday is going to end up with a similar result, but via different route. Youtube linky

klipless wrote: Love this build! I vote big block. I'm not a huge fan of the 6.slow in any application (try driving it in a 3500HD dually...painful). I don't know of any completed examples of this swap, but Fred from Dirt Everyday is going to end up with a similar result, but via different route. Youtube linky

I was doing a lot of homework to possibly 8.1 swap my old truck - I like what they did to the alabama army truck. I love dirt every day! I will have to check this out.

I'm really on the fence of just getting it fixed or just diving into this. the ideal time frame is to have this truck towing by mid October so I can drive 550 miles up to the upper part of the UP in Michigan for LSPR (Lake Superior Performance Rally) and use it partially as a camping vehicle on the way to the event.

also the images are hosting through my google drive which may be some of the issue, the others are rando internet googling...