6.6 Gas L8T Engine Swap in 2015 Suburban

[L8T BURB]

Looking good! Are those non factory headlights? They look good.

They are factory headlights. I removed the chrome strip on top and had it paint matched. Then had the headlight lens sanded/cleared.

 

[adventurenali92]

They are factory headlights. I removed the chrome strip on top and had it paint matched. Then had the headlight lens sanded/cleared.

Interesting. Maybe it’s just the photos but it didn’t look like they had the horizontal LED strip in the middle so I was confused lol.

 

[B-train]

Man this thing has been a BLAST! I've honestly only floored it from a dead stop 5 times or so since I've had it back, and it makes me grin ear to ear each time. The torque that this 6.6 makes down low is just nuts!

The only real thing I'm looking to do differently is with the exhaust. During the swap, we decided to gut the stock 5.3 cats, as they didn't seem to be handling the new engine very well. Got the patented "rotten eggs" smell during the first drive after swap, so we gutted them which cleared that issue, but the raw fuel smell from the tailpipe is really becoming an aggravation to me.

I do have the cats/downpipes from the 6.6 that I believe I will have welded in this Spring. Likely just going to use the two upstream cats, and then maybe get 3 inch pipe custom ran after the cats to the back. Still unsure on a muffler, but possibly a flowmaster or magnaflow.

In the meantime, I have been doing an "RST conversion". At least that's what I'm calling it. Complete with color matched LTZ grill, black mirror caps, black badges, black D pillars, and RST rims. Also trimmed the lower valance to 3 inches. I will include pics below of the cosmetic mods. Be sure to like, comment, and subscribe to my YouTube channel. It's been VERY cold here, so I've been slow about posting new content lately but I'm looking to get back to it soon! Planning to get some full throttle runs for the next videos I'll be posting!

Youtube link: https://youtube.com/@L8T_BURB?si=4noRWfDzbbK78ckn

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Thanks for the update! Looks good

How has the mpg been?

Also, can't the fuel tables be leaned out to get rid of the richness? I know all newer stuff runs rich to keeps the cats hot, but I would think that some of that additional fuel could be scaled back. You'll still have the old school smell with no cats, but maybe there's a happy medium?

 

[L8T BURB]

Thanks for the update! Looks good

How has the mpg been?

Also, can't the fuel tables be leaned out to get rid of the richness? I know all newer stuff runs rich to keeps the cats hot, but I would think that some of that additional fuel could be scaled back. You'll still have the old school smell with no cats, but maybe there's a happy medium?

The MPG has suffered, but only a little. We are in cold season here in KY, so there's been a lot of idling and such so it's been tough to get a good true read on MPG. I am estimating it's lost maybe 1.5 MPG in town, but I think I gained that much or more on highway driving. With the added displacement and torque, it hardly grunts at all when pulling hills. Most times doesn't even shift down unless it's a big hill.

As for the fuel, I believe it's leaned as much as it can be. Like you referenced, it's more of that "old school smell" that I'm not too big a fan of. I didn't mind it much at first, but during the cold season with idling more, defrost on at stop lights tends to allow some of that smell to creep into the cabin. Also picking up kids from ball practice, I'll have the Suburban idling and when they open the liftgate, it's almost instant that it comes into the cabin, and the kids do fuss about it a little. Therefore I think welding the 2 upstream cats in will likely be my best option.

 

[B-train]

The MPG has suffered, but only a little. We are in cold season here in KY, so there's been a lot of idling and such so it's been tough to get a good true read on MPG. I am estimating it's lost maybe 1.5 MPG in town, but I think I gained that much or more on highway driving. With the added displacement and torque, it hardly grunts at all when pulling hills. Most times doesn't even shift down unless it's a big hill.

As for the fuel, I believe it's leaned as much as it can be. Like you referenced, it's more of that "old school smell" that I'm not too big a fan of. I didn't mind it much at first, but during the cold season with idling more, defrost on at stop lights tends to allow some of that smell to creep into the cabin. Also picking up kids from ball practice, I'll have the Suburban idling and when they open the liftgate, it's almost instant that it comes into the cabin, and the kids do fuss about it a little. Therefore I think welding the 2 upstream cats in will likely be my best option.

Good info. I second the install of the other cats. Can the Y pipe be used? I didn't read through the whole thread again, so maybe I missed that. I would assume that using the bigger diameter pipe as much as possible would be beneficial. Those girls like to breathe

 

[TollKeeper]

By the sound of it, a custom exhaust from the manis out, using the cats are in order.

Just to help the engine breath better, and get those nasty CO's out the tailpipe more effectively.

 

[L8T BURB]

If, and it is a BIG if....I was to consider selling this thing, any idea on what someone would be willing to pay? It being a highly specific, 1 off type of build, and the mileage, I'm concerned I'd get burned on any sort of good sale price. This thing is a MONSTER since the engine swap.

Highlights as follows...

2015 Suburban, 2WD, 189K miles.
Tan leather interior w/captains chairs
Factory overhead Blu-Ray player

Just 3k miles ago the following repairs were done...

Brand new 6.6 engine transmission (No DOD/AFM)
Brand new 6L90 transmission
New driveshaft
New ball joints, inner and outer tie Rods, new front shocks/struts, new rear shocks
New steering wheel (old one had peeling leather)
New motor mounts

Cosmetic stuff
22 inch RST wheels/tires from a 2022 Suburban w/3k miles
2022 Suburban RST wheels w/3k miles
5% tint on all windows w/5% strip on windshield

All said, engine and transmission cost was $7500, other miscellaneous parts another $1000, and total labor cost for all repairs was $6500. Crazy...I KNOW lol! It's basically a bulletproof Suburban at this point though.

 

[Tonyrodz]

If, and it is a BIG if....I was to consider selling this thing, any idea on what someone would be willing to pay? It being a highly specific, 1 off type of build, and the mileage, I'm concerned I'd get burned on any sort of good sale price. This thing is a MONSTER since the engine swap.

Highlights as follows...

2015 Suburban, 2WD, 189K miles.
Tan leather interior w/captains chairs
Factory overhead Blu-Ray player

Just 3k miles ago the following repairs were done...

Brand new 6.6 engine transmission (No DOD/AFM)
Brand new 6L90 transmission
New driveshaft
New ball joints, inner and outer tie Rods, new front shocks/struts, new rear shocks
New steering wheel (old one had peeling leather)
New motor mounts

Cosmetic stuff
22 inch RST wheels/tires from a 2022 Suburban w/3k miles
2022 Suburban RST wheels w/3k miles
5% tint on all windows w/5% strip on windshield

All said, engine and transmission cost was $7500, other miscellaneous parts another $1000, and total labor cost for all repairs was $6500. Crazy...I KNOW lol! It's basically a bulletproof Suburban at this point though.

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Make sure you have proof of the actual mileage on the new drivetrain, and what the odometer said once the drivetrain was installed and running. So even though the body has 189k, the drivetrain doesn't. I couldn't even guess what someone would be willing to pay for it. What would a stock comparable vehicle in similar condition go for? I'd go from there, and maybe add another 10k--or a little less. That's just off the top of my head.

 

[TollKeeper]

If it was 4x4, I would be considering it!

 

[Marky Dissod]

Keep in mind, this is a 6.6L engine and a 6L90 trans ... neither of which were ever meant to be in this vehicle ...

Every 4.8L, 5.3L. 5.7L, 6.0L, 6.2L, 6.6L, and 7.0L shares extremely similar external dimensions.
The whole point of a small-block.
If you don't already know for a fact that a jacqueswhole has swapped a 5.3L into a 'vette, just to get away with selling it to someone unawares ...
Now you know. If you can't believe it, DuckDuckGo it (googl me ars).
As for the 6L90, he did such a good job with that crossmember, the only people who will spot it are transmission and/or crossmember experts.
Never meant to be? They look right at home!

Speaking of 6.6L swaps, dig these DuraMax conversion firms:

Predator Duramax Suburban

predatorinc.com

Duramax Specialties, LLC

Thank you for your patience, this page is currently under development. Feel free to call or visit us at the links above.

duramaxsuv.com

Home - DMAX SWAP - Duramax Swap

dmaxswap.com

Precision Fabrication Plus Inc.

Specializing in '60-'91 GM Duramax Swaps and '01-'18 GM IFS DELETE Conversion Systems. From mild to wild we do it all!

precisionfabricationplus.com

Blame CAFE MpG standards for the fact that we can't go to a dealership and order powertrains like a Five Guys burger.

If you were to consider selling it, consider / research how well Suburban 2500s hold their value.
In other words, when you do sell it, you'd better have sold it for enough money to feel really good about it - because you'll STILL regret it.