2016 Tahoe LTZ - Swapping to the 6.6L L8T

[Too_L8T]

How did I get here?

Purchased a 2016 Tahoe LTZ with about 75k miles on it. Been a GREAT vehicle. Thanks to research mostly on this forum, I disabled AFM with a Range OBD dongle the day I bought it. Ran basically trouble free with routine maintenance to 175k miles when the transmission gave out. Typical parts replaced as needed throughout that time - shocks, tires, etc. Never had it in a shop before the trans gave out. Has a leveling kit, BFG KO3's, and a Borla cat back exhaust. Everything else is stock. It was moms taxi until her dad gifted us a '25 suburban premier

I tow a camper with it, so my transmission shop rebuilt it with HD parts - shift kit, torque converter. Had to replace 4,5,6 steel and used this master kit. They tuned out the AFM as well.

But just my luck, I get the truck back and within a week i get a squeaky lifter. It sounds like nails on a chalkboard. Doing some research, I was about to do a cam job, AFM delete etc. but stumbled across a few threads and videos of guys dropping the L8T in these trucks, with minimal mods.

This isnt going to happen quickly, but i will update as work is done. I am going to hopefully limp this motor to Jan 26 while i prep the new motor. My local tuners are booked out 3-4 months anyways.

So, to begin this project I found what i think is a pretty good deal on eBay of all places. $4500 for a brand new L8T on a pallet. He's got 5 more at this price as of 8.2.25 if anyone else is looking. Plan is to put it in the garage and toss parts at it here and there, put everything on it that I need for the swap. I will be putting a BTR cam - most likely the milder "torque" cam (I tow - and the power is in the low/mid range) I have no need for ripping around at 4500 rpm really. I love the chop though so i may change my mind.

Any suggestions for parts - please post below. Looks like aftermarket headers options is very slim pickins - i dont think i want to spend half of what i spent on the motor on headers. might just rock the GM headers for now.

Thanks for following along on this journey!

 

[B-train]

Here's your post......

Keep us updated with info and pics please.

 

[Marky Dissod]

$4500 for a brand new L8T on a pallet. He's got 5 more at this price as of 8/2/25, if anyone else is looking.

'Ol EESH HIT!

I will be putting a BTR cam - most likely the milder "torque" cam (I tow - and the power is in the low/mid range).
I have no need for ripping around at 4500RpM really. I love the chop though so i may change my mind.

Looks like aftermarket headers options is very slim pickins - i dont think i want to spend half of what i spent on the motor on headers.
might just rock the GM headers for now.

Normally I 'ALWAYS' suggest more axle gear because it ALWAYS improves towing / hauling & durability / longevity;
in the L8T's case keeping the OE axle gears will improve unladen MpGs when driven conservatively ...
but I'd always choose better axle gears over a cam; better gears pay for themselves over time by helping the engine / transmission last longer.

GM likely spec'd L8T exhaust manifolds to be more restrictive over 4000RpM than, say, 6.2L CAR exhaust manifolds, or LS7 exhaust manifolds.
Would not be surprised if a set of mid-length-tube or long-tube headers turned out to improve power over 4000RpM compared to L8T manifolds.

 

[Too_L8T]

Awesome thanks!!!! not sure what happened there. it was gone.

Its got the max trailering package with the 3.42 gears. thought about 4.10 but maybe later. I am leaning 6.6 factory headers. I am going to keep the factory cats/y pipe for now. the only other headers i can find are AFE power.

 

[Marky Dissod]

It's got the max trailering package with 3.42. thought about 4.10, but maybe later.

With an L8T, 3.73'd be enough even with taller tires, unless you also plan on towing over 10,000lb, or racing for profit/glory, in which case maybe 4.10.
Vehicles that originally came with the L8T ('2500' or '3500'), usually came with either 3.73 or 4.10, FYI.

I am leaning 6.6L GM OE headers. I am going to keep the factory cats/y pipe for now. the only other headers i can find are AFE power.

Might be educational to dimensionally compare other GM OE 6.2L manifolds, or even 7.0L LS7 or supercharged 6.2L manifolds.
AFe power are likely more expensive than any GM OE option.

 

[Too_L8T]

With an L8T, 3.73'd be enough even with taller tires, unless you also plan on towing over 10,000lb, or racing for profit/glory, in which case maybe 4.10.
Vehicles that originally came with the L8T ('2500' or '3500'), usually came with either 3.73 or 4.10, FYI.

Might be educational to dimensionally compare other GM OE 6.2L manifolds, or even 7.0L LS7 or supercharged 6.2L manifolds.
AFe power are likely more expensive than any GM OE option.

Racing for profit and glory or towing 10k will never happen lol. Its still just a Tahoe. The camper is only 6000 lbs. But it would be nice getting her up and going without screaming the engine and for towing through the mountains. I rarely “get on it”. But I also like overkill for some reason…

 

[Marky Dissod]

Racing for profit and glory or towing 10k will never happen. Its still just a Tahoe. The camper is only 6000 lbs.
But it would be nice getting her up and going without screaming the engine and for towing through the mountains. I rarely 'get on it'.

Then 3.42 will do quite nicely. You may find yourself 'getting on it' LESS, even without 3.73.

 

[fozzi58]

I say go for the Kooks LTH! lol

However, of more concern, that G80 rear probably isn't going to last with the extra torque that L8T puts out unless you are super gentle with it. Make budget for a replacement carrier.

 

[Trey Hardy]

How did I get here?

Purchased a 2016 Tahoe LTZ with about 75k miles on it. Been a GREAT vehicle. Thanks to research mostly on this forum, I disabled AFM with a Range OBD dongle the day I bought it. Ran basically trouble free with routine maintenance to 175k miles when the transmission gave out. Typical parts replaced as needed throughout that time - shocks, tires, etc. Never had it in a shop before the trans gave out. Has a leveling kit, BFG KO3's, and a Borla cat back exhaust. Everything else is stock. It was moms taxi until her dad gifted us a '25 suburban premier

I tow a camper with it, so my transmission shop rebuilt it with HD parts - shift kit, torque converter. Had to replace 4,5,6 steel and used this master kit. They tuned out the AFM as well.

But just my luck, I get the truck back and within a week i get a squeaky lifter. It sounds like nails on a chalkboard. Doing some research, I was about to do a cam job, AFM delete etc. but stumbled across a few threads and videos of guys dropping the L8T in these trucks, with minimal mods.

This isnt going to happen quickly, but i will update as work is done. I am going to hopefully limp this motor to Jan 26 while i prep the new motor. My local tuners are booked out 3-4 months anyways.

So, to begin this project I found what i think is a pretty good deal on eBay of all places. $4500 for a brand new L8T on a pallet. He's got 5 more at this price as of 8.2.25 if anyone else is looking. Plan is to put it in the garage and toss parts at it here and there, put everything on it that I need for the swap. I will be putting a BTR cam - most likely the milder "torque" cam (I tow - and the power is in the low/mid range) I have no need for ripping around at 4500 rpm really. I love the chop though so i may change my mind.

Any suggestions for parts - please post below. Looks like aftermarket headers options is very slim pickins - i dont think i want to spend half of what i spent on the motor on headers. might just rock the GM headers for now.

Thanks for following along on this journey!

I don’t know if speed engineering makes headers for that motor but that’s what I’ve always used on all my trucks and my buddy’s trucks. Their cheap their stainless fitment is great and under 400$ for the headers is a good deal.
Btr is good but to be honest 90% of their stuff are Chinese crap. I know this because my race car friend has been robbing 243 heads out the junk yard and rebuilding them with “btr springs” and a cam and selling them on marketplace. He’s been getting the same exact Brian tooley racing parts from alibaba or one of them overseas dirt cheap company so he usually has 150-200$ into the heads and parts to rebuild them and flips them for 375$ or so. He literally said they come in the same exact box as the Brian tooley stuff but instead of 150-200$ he gets it for like 50$ (for the springs) just throwing it out there if your on a budget

 

[Trey Hardy]

Awesome thanks!!!! not sure what happened there. it was gone.

Its got the max trailering package with the 3.42 gears. thought about 4.10 but maybe later. I am leaning 6.6 factory headers. I am going to keep the factory cats/y pipe for now. the only other headers i can find are AFE power.

Compare the headers off that engine with some of the other engines you might be able to make some 6.2 headers work on it if it’ll bolt up

 

[Too_L8T]

I don’t know if speed engineering makes headers for that motor but that’s what I’ve always used on all my trucks and my buddy’s trucks. Their cheap their stainless fitment is great and under 400$ for the headers is a good deal.
Btr is good but to be honest 90% of their stuff are Chinese crap. I know this because my race car friend has been robbing 243 heads out the junk yard and rebuilding them with “btr springs” and a cam and selling them on marketplace. He’s been getting the same exact Brian tooley racing parts from alibaba or one of them overseas dirt cheap company so he usually has 150-200$ into the heads and parts to rebuild them and flips them for 375$ or so. He literally said they come in the same exact box as the Brian tooley stuff but instead of 150-200$ he gets it for like 50$ (for the springs) just throwing it out there if your on a budget

its probably the chinese ripping off btr not the other way around. ive made the decision just to go with gm headers. Not going to be a dyno queen

 

[Too_L8T]

Compare the headers off that engine with some of the other engines you might be able to make some 6.2 headers work on it if it’ll bolt up

its not coming with manifolds thats why i need to get some. just ships with water pump from what it looks like in the pics

 

[blondie70]

I have the BTR "NSR" cam in my 5.3. Got a heavy duty torque converter also. Sure wish I would have gotten the higher RPM stall speed option on the converter. The cam wants to surge when idling. Had no idea this would occur. You may want to consider this with your converter !!?? and avoid drivability problems like I am having.

 

[Too_L8T]

I have the BTR "NSR" cam in my 5.3. Got a heavy duty torque converter also. Sure wish I would have gotten the higher RPM stall speed option on the converter. The cam wants to surge when idling. Had no idea this would occur. You may want to consider this with your converter !!?? and avoid drivability problems like I am having.

Can you talk more about this? What is stall speed, cant this be tuned?

 

[tooleyondeck]

ive made the decision just to go with gm headers. Not going to be a dyno queen

Keep in mind that OEM L8T manifolds are designed for HD trucks. Those engines sit up higher than your Tahoe 5.3 so the manifolds have a longer "drop" on them. You don't want to end up with headers that don't clear your subframe or stick down below your oil pan. I can measure mine or shoot you some pics if it would help, I have an L8T Silverado.

 

[Too_L8T]

I was going to go with the 6.2 denali manifold not the 6.6.

the friggen engine harness for my tahoe is over $600!! every other model is like 300. so i may be stuck using the existing once i pull it

 

[tooleyondeck]

unless your wiring harness is damaged is there a reason to get a new one?

 

[Too_L8T]

unless your wiring harness is damaged is there a reason to get a new one?

I wanted to fully prep as much as possible so I could just yank it out and drop it in. Plastic is brittle sometimes too I’d hate to have a connector holding up the install.

 

[Too_L8T]

Delivery Day!

 

[Too_L8T]

I found some new genuine gm manifolds pulled from a new engine, on ebay for $200 both left and right. i pulled the trigger on them since there was only 2 sets left. Anyone think it would be worth returning for a set of BBK shorty headers for $599? im thinking about a 210 btr cam but havent decided yet.