2008 Suburban HD - 8.1L swap (frankenburban 2.0)

[fidelity101]

I sold my K20 earlier this in hopes of avoiding another project so I decided to buy a low mile (54K) 3/4 ton suburban from the newer body style. Since the goal was to be mostly my tow and camping pig

Here are the two side by side before I leave the old burb behind

cloth, "bench" seats with a LY6 6.0L v8 powered 6 speed 4wd? what could go wrong? its the HD so it has all the towing beefyness I like and need.

Needed some basic work like brakes/tires/shocks - nothing crazy after sorting all that out I started hearing a noise (that I could not hear earlier due to loud hard tires and a vibration caused by sticking caliper slides) and it slowly got louder... But at the time I paid no attention to it and went on my merry way...


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:

 

[fidelity101]

So I turned it into this!

and then we went to the beach for the weekend

but then the noise got louder... and it was certainly knocking (now 57k miles)

After doing a bunch of homework and deciding I really did not want to put another small block in this because it just felt too slow, needed WOT all the time when towing (which it did) but I would prefer to do it with some ease and little less throttle and better power when I need to haul larger loads.

problem is, they didn't offer the 8.1 in the GMT900 it only lasted up to 2006 in the trucks (GMT800) so the electronic architecture is a bit different.
cam sensor is 4x signal instead of 1x
crank sensor is 58x instead of 24x
all of the big block sensors are pipe thread, whereas the LY6 runs metric

however some things are the same:
MAP sensor
IAT sensor
air conditioning compressor
power steering

and some things are electrically or fundamentally the same ( make a new jumper connector)
Oil pressure
water temperature

and other things need a simple adapter, like the throttle body to go from a 3 bolt manifold style to 4 bolt throttle body style.

 

[fidelity101]

So I took the plunge and purchased a low mile drop out 8.1 from a semi local yard. and begun to tear into it.

GM offers a trigger kit so you can run the big block on the gen IV ECM. this kit includes a new timing cover, cam/crank sensors and the new reluctor wheel. now the CPK will be taken from the front of the engine instead of behind and it upgrades to a double roller which seems fine.

Here is a side by side comparison for the gen VII (2004+) BB timing cover next to GM's trigger kit, the cam sensor spot is exactly the same and the crank area has a slightly larger volume. There are some differences for the 01-03 front timing cover but if you're doing this swap for the gen IV ECM it won't matter, but if you have the late 03/04+ style you have an extra cam sensor which couldn't hurt to keep in your box of misc truck stuff just in case you get a failure on road.

The one on the left you can see where the stock oil pan seal seats against and clearly the two seem different in this location but in-fact: this cover bolts right on.

This space is for the large 58x trigger tooth wheel so that the CKP can pick up the correct signal. the extra sensor boss at the bottom is a dead give away, you can install the sensor on after the cover but is much easier to install it first then place the cover assembly on.

When you look at the back side you can see the provision for crank wheel and that they have given it extra space but it looks like it won't fit on because the stock cover has a flat spot whereas the new one has a valley.

You can remove the stock timing cover without loosening the oil pan, but you cannot install/remove the new cover without loosening the oil pan bolts because the seal rides in that valley and you basically have the outer ridge of the cover over-flush to the seal/pan. Instead of just riding along side the seal it wraps it in a C shape, so this may even be less prone to leaking perhaps - which is a bonus.

Here you can see the gap where the ridge will sandwich between.



and this is the engine on a stand with the cover bolted on.

I had to loosen the pan bolts to install it like I mentioned but once you set the cover on and tighten the pan bolts it becomes quite the sandwich and everything fits together perfectly. (sorry for the blurry photo)

and no thats not a crack thats a casting mark, the photo just likes to highlight the shadow from the raised area.


which means it is unlike the old big block:

so right now I have this going on:

its a roll pin instead of a woodrift key?! who the hell decided on that?

but the fear assumptions confirmed.

if this was a woodrift key, we would have been installed the crank pulley by now

Here you can see that the gear totally uses the roll pin, however there is a bit of a gap in the recessed area on the crank so I have a few ideas...

 

[Chevy305]

I like where this is going. Please keep posting sweet tech updates

 

[78K30]

Sounds like an interesting build. Following for updates as well

 

[fidelity101]

Absolutely!


I was waiting for the dust to settle from the madness of this weekend’s wrenchfest before I could finish the update post, digest the situation etc.

Pulling the engine was fairly straightforward newer vehicle had no rust so that was nice. I learned a few tricks so if you are ever removing an engine from a modern chevy truck these should help.

If you remove the core support, you do not need to remove the hood but you need to loosen one fender so you can move it inboard/outboard to get the core support out. I see the people at duraburb pick the whole body off the frame to do their swap which would be a great idea too but I don’t have the equipment to do so or the space.

By far the hardest part is the bolt for the bellhousing at top dead center. You will need a few feet of various extensions and ideally 2 to 3 u-joints with a medium well (deep works but a medium one would be best) socket. The problem is that the cab comes together near there as 2 stamped pieces of steel spot welded together which tends to hang up on the u-joint when trying to remove the bolt. When you remove the engine, beat this with a hammer inward so you have that extra 1” of room to turn a socket for reinstall because the area is a tight fit. If you have a 1” bodylift you won’t need to do this at all and everything will be a little easier. I kind of want to do one now actually…

Then Loosen the trans crossmember bolts, support the pan or bellhousing with a floor jack.


Now that you have removed the bellhousing bolts To get the engine out you need to lower the front axle about 2” so just remove the bolts attaching it to the frame on the passenger side and the big eyelid bolt at the top. You can let it hang but I lightly supported it with a floor jack.



Then with the engine out, clean everything! I have a pretty bad power washer but it managed to take the grime and paint right off the frame to bare metal! I hate working on oily grimey parts, it always makes it much worse. Kind of surprised this much came off, makes me think it wasn’t applied very well when the vehicle was built.

So now I gotta paint it and let it dry, meanwhile I will prep the engine for install back into the chassis but before I can do that

Meanwhile I test fit the engine to see if it physically fits in the cab and managed to put a few bellhousing bolts in to see, and it fits better than the 6.0 the intake manifold isn’t a mile tall. The rumors are true. These HD frames are the same from 2000/2001-2013 so mechanically this bolts in.

The engine mounts and engine mount plates are unique between the big block and small blocks. However the big block shares the same engine mount and mount plates between the 6.6 duramax – and they did offer the Duramax throughout the GMT900 lifespan and backs up the claim that Duramax engines were designed by chevy instead of like a cummins in a dodge where they just told ram to piss off and make their engine fit because we won’t change ours.

So with the right engine mount and mount plate this bolts in, bellhousing bolts up – everything is pretty cut and dry GM parts bin. Here is a side by side between the two

If you don’t want to use the big block mounts/plates – you can always fab your own but I prefer the easy button method. Otherwise if you use the small block stuff MOST of the bolt holes line up so it wouldn’t be too hard but definitely not worth it when there are thousands of junk trucks around but as you can see they are pretty similar.

 

[fidelity101]

So that being the hardest part we start then moving to the other compatibility items:

1. Alternator – swaps right over.

2. Oil pressure sensor – electrically the same and just a different thread style so this literally plugs in! (as shown below) the connector fits, may not be the exact one but it’s a tight fit and robust fit for sure.

3. Injectors – not sure how different they really are (aside from obvious electrical hookup) but they fit on the L18 rail no problem and that’s all I cared about. Again the goal is to keep it as close to original as possible to minimize any elaborate custom software reflashing.

The next big item (literally) is the radiator. They are different between the 6.0 and the 8.1. the 6.0 is common between GMT800 and GMT900. The inlet/outlet are a little larger on the 8.1 and the core is physically larger (~10%) but the other issue is that the oil cooler lines for the engine oil are much larger.

I’m afraid of making a line adapter to avoid changing the oil characteristics/flow etc. The 8.1 I think needs the 8.1 radiator then the coolant hoses all make sense and bolt together so I can have heat to the heater core and no hose looks spliced and out of place. Problem is with the 8.1 parts cost more for no good reason other than volume on sales is much lower than the LS stuff. 6.0 HD radiator is 160 bucks, 8.1 is 330+. LS engine mount is 45 bucks, 8.1 engine mount is 90. Notice a trend? But anyways if I just man up and order the 8.1 coolant system (essentially) everything will bolt up. The trans cooler line fittings are the same for both the 8.1 and 6.0 so that’s plug and play for me at least. Because the engine is larger the fan shroud is smaller, I believe the clutch fans will bolt on interchangeably but I will find out for sure. Essentially the 8.1 coolant system is unique to it but the chassis isn't and this being a GM era of economic decline the accountants there figured you just need to make as much stuff common or interchangeable as possible and it became a brilliant manufacturing strategy to cut costs.



Still lots to do though – white board helps you stay on track or remember things.

With the engine out I will prep the wire harness so I can access everything easier then bolt everything together. Still a few more things to adapt and likely a few wire extensions. Once I figure that aspect out entirely I will post the modifications required.

 

[GWeakland620]

Cool stuff!

 

[Chevy305]

Nice work so far.

About the injectors, the 8.1 injectors are bigger than the LY6 injectors. I've even heard of people swapping in the 8.1 injectors onto a hotrodded 6.0 to support added horsepower. So dropping down to 6.0 injectors will probably max them out. I don't have exact figures nor have I messed with them before but this is what I've read.

 

[sreidmx]

The tune on this should be pretty interesting, hope you have a good guy local..

 

[fidelity101]

Nice work so far.

About the injectors, the 8.1 injectors are bigger than the LY6 injectors. I've even heard of people swapping in the 8.1 injectors onto a hotrodded 6.0 to support added horsepower. So dropping down to 6.0 injectors will probably max them out. I don't have exact figures nor have I messed with them before but this is what I've read.

I've heard the other way around... and with stock big block power I cant imagine that the LY6 injectors would be all that stressed.

LY6 is 300-330hp and 385 ft lbs (wikipedia claims 365hp/385 ftlbs) and SAE claims another value:

aaaand edmunds says 352hp/383tq


The L18 is 330hp and ~450ft lbs

The tune on this should be pretty interesting, hope you have a good guy local..

Should be easy, but I do have several people to choose from. Also by my location (Detroit) getting an LS engine tuned in the area is pretty easy.

 

[sreidmx]

I've heard the other way around... and with stock big block power I cant imagine that the LY6 injectors would be all that stressed.

LY6 is 300-330hp and 385 ft lbs (wikipedia claims 365hp/385 ftlbs) and SAE claims another value:

aaaand edmunds says 352hp/383tq


The L18 is 330hp and ~450ft lbs

Should be easy, but I do have several people to choose from. Also by my location (Detroit) getting an LS engine tuned in the area is pretty easy.

Right on this is gonna be bad ass

 

[fidelity101]

got the image wrong above, this is the correct injectors:

the big connector is for the Ly6 and the small connector is for the L18

 

[Truckman4life]

Why use the 6.0L injectors and not just fix the harness to run the 8.1L injectors?

 

[fidelity101]

Why use the 6.0L injectors and not just fix the harness to run the 8.1L injectors?

The 6.0 injectors are plug and play and when I look up the specs for the 8.1 injectors are rated between 25-

LY6 = 12580681 injector part# 30lb/hr
L18 = 25343789 injector part# 26-32lb/hr depending what source I can goolge up...

The less I have to do and the more OEM it is the easier everything should be.

 

[Truckman4life]

Sounds like a good plan. I figured that was why, I just didn't think they would be rated that close to a 6.0L

 

[jeff in co]

Cool build, subscribed.

 

[fidelity101]

Sounds like a good plan. I figured that was why, I just didn't think they would be rated that close to a 6.0L

Yeah I am getting a friend at GM run the numbers to double check.

Yeah the problem with the 8.1 stuff everyone is just a bunch of keyboard warriors and they go 6L RULE!!!!! BIG BLOCKS SUCK!!! MAKE MORE POWER WITH AN LS - SUPERCHARGE IT BROOOO, SLAP A SLOPPY TURBO SETUP IT! blah blah blah but its all in the application intent... I do a lot of towing with this rig so its not pleasant to wind out the 6.0 and hard shift full power at 5krpm to get up to speed towing 7klbs. With this making more ft lbs at 1000rpm than the ly6 at peak tq it should be a towing monster with ease. The only downside is that the replacement parts are expensive in comparison due to the sheer volume differences but prices aren't outrageous and yes the aftermarket is small but I'm not looking for crazy power or anything. Should this engine fail I will just go with a cam/rocker setup from raylar and some headers and call it a day.

I like the power of the 6.0 but it just needs to be doing that power at 2500 less RPM.

Other alternative option is duraburb but thats 6 months delay a wrecked 6.6 truck and 25k...cash. So not really an option.

 

[Truckman4life]

Yeah my buddy has a 6.0 truck and tows 10k in the mtns in Utah. Wound up all the time is an understatement. I was contemplating an 8.1 for cheaper maintenance and parts than a diesel but I will probably get a 35-40' toy hauler in the future combined with mtns and 6 percent grades and it would just not be as good as a diesel for me. Cool build though.

 

[fidelity101]

Yeah i mostly tow in the Midwest or Appalachians at most. I would hate an NA 6L in the mountains towing anything....