Gotta do a Rebuild, Gonna Upgrade Too

[intergalactron]

So... My motor has to come out due to an AFM lifter failure. At 120K miles, I figure a total rebuild is in order. And if I have to do a rebuild, I'm gonna upgrade a bit. Nothing wild, just a little more pep. Starting to research parts. Anyone got experience with this?

1. Without a doubt, the AFM comes off. No brainer there.
2. What are the pros and cons of removing the VVT?
3. Cam, lifter, valve springs, etc., suggestions?

 

[Joseph Garcia]

Texas Speed and Summit Racing have kits available to replace AFM. Give one of them a call and see what they include in their kits.

 

[Geotrash]

So... My motor has to come out due to an AFM lifter failure. At 120K miles, I figure a total rebuild is in order. And if I have to do a rebuild, I'm gonna upgrade a bit. Nothing wild, just a little more pep. Starting to research parts. Anyone got experience with this?

1. Without a doubt, the AFM comes off. No brainer there.
2. What are the pros and cons of removing the VVT?
3. Cam, lifter, valve springs, etc., suggestions?

I don't have any direct experience with the LT motors, but on the GenIV LS 6.2 in my 2012 (L94), I went with a 3-bolt cam (no VVT) and am thrilled with it. VVT on the LS engines was only good for maybe 15hp, which is easily made up for with a bigger "truck cam". Maybe someone who's upgraded their L86 will weigh in.

 

[intergalactron]

Did more tear-down over the weekend. There was an obvious difference between the driver side and passenger side as far as tightness of rocker bolts, head bolts, etc. Leads me to believe that this motor had work done on the driver side before I got it. I purchased the truck in February 2021, with ~42000 miles.

 

[intergalactron]

No going back now.

 

[intergalactron]

Does anyone know what size the head of the rod bolts are?

 

[intergalactron]

Does anyone know what size the head of the rod bolts are?

Looks like they are a 12mm Hex head. Can anyone confirm? I was worried that they were a 12-point or something weird.

 

[Geotrash]

Does anyone know what size the head of the rod bolts are?

Should be 12mm 6-point.

 

[Marky Dissod]

What are the pros and cons of removing Variable Cam Timing?

My understandings:
GM's Variable Cam Timing retards or advances the cam relative to the crank
How GM uses it, chief benefit is MpGs in conjunction with advanced timing,
2ndary benefit is improved very low RpM torque.

Some aftermarket cams require limiting / reducing VCT's 'degrees of authority',
others require complete VCT removal; depends on the cam & valvesprings chosen.
Stiff valvesprings overcome VCT.

(Older I get, more I'd prefer a 6.0L or 6.2L, much moreso for strength UNDER 3500RpM -
I drive like I'm always running late, and even with an aftermarket pcm tune,
I STILL spend most of the time UNDER 3500RpM,
so that's where I'd want the biggest improvement - the moment I hit the pedal, not after.
I'd keep consider keeping VCT, maybe with a VCT limiter, to improve low RpM.
I'd not sacrifice ANY low RpM torque for more power at higher RpMs
because of how little time I spend over 4500RpM.)

 

[intergalactron]

Looks like they are a 12mm Hex head. Can anyone confirm? I was worried that they were a 12-point or something weird.

11mm hex head turned out to be the size.

 

[intergalactron]

New question today... The cam I chose (BTR Stage II) will require a tune. There's a guy local to me that is well known and has a good reputation. But I'm a little concerned about doing dyno pulls on a freshly rebuilt motor. Should I be?

Secondarily, I see that HP Tuners has a 'remote tuning' setup. Anyone have any experience with that?

 

[Marky Dissod]

... The cam I chose (BTR Stage II) will require a tune.
There's a guy local to me that is well known and has a good reputation.
But I'm a little concerned about doing dyno pulls on a freshly rebuilt motor. Should I be?

Secondly, I see that HP Tuners has a 'remote tuning' setup. Anyone have any experience with that?

1. The rest of the engine is properly broken in right? Until it's tuned to yours and your tuner's satisfaction,
no SUDDEN throttle changes.
The difference between 0%-100% TPS in 0.1sec, vs 0%-100% TPS in 1.0 secs matters.

2. No remote tuning experience. I've sat next to the driver while reading what the laptop says in realtime.
I imagine a smart enough guy'd understand laptop recordings regardless of when they were made.

How many questions have you asked this tuner?

 

[intergalactron]

1. The rest of the engine is properly broken in right? Until it's tuned to yours and your tuner's satisfaction,
no SUDDEN throttle changes.
The difference between 0%-100% TPS in 0.1sec, vs 0%-100% TPS in 1.0 secs matters.

2. No remote tuning experience. I've sat next to the driver while reading what the laptop says in realtime.
I imagine a smart enough guy'd understand laptop recordings regardless of when they were made.

How many questions have you asked this tuner?

1. Still theoretical, but most likely it'll be new rod and main bearings, new cam (maybe new cam bearings), new lifters, new push rods, new oil pump, new piston rings. Re-using old pistons, con rods, high pressure fuel pump. Cylinders will be honed. Everything will be cleaned before re-assembly.

I haven't spoke directly to the tuner yet. He's weeks out, so I reserved a spot in line. His assistant didn't understand my questions/concerns. An in-person conversation is definitely on my to-do list.

 

[Marky Dissod]

1. Still theoretical, but most likely it'll be new rod and main bearings, new cam (maybe new cam bearings), new lifters, new push rods, new oil pump, new piston rings.
Re-using old pistons, con rods, high pressure fuel pump. Cylinders will be honed. Everything will be cleaned before re-assembly.

I haven't spoke directly to the tuner yet. He's weeks out, so I reserved a spot in line.
His assistant didn't understand my questions/concerns. An in-person conversation is definitely on my to-do list.

New cam, new cam bearings; don't maybe it.
Most assistants don't, unless they are also experienced tuners.

When you bought it from GM, GM 'said', "this is the tune, take it or leave it'. You were so unhappy with it, that you went and changed the CAM.
If you chose it well - if it actually suits your expectations - then it'll be simple explaining to your tuner what you want and what you don't.

Don't forget that you have TWO shift tables: Normal, and Tow / Haul - two distinct personalities available.
My 'Normal' table makes GM's 'Normal' look like GM thinks the driver is in their late 70s.
My 'Tow / Haul' table is more like a 'Performance / Sport' table, because I never tow / haul.

 

[2017sltXL]

No going back now.

FWIW, when I did my delete recently I went with a BTR Stage 1 for my 2017 Yukon, L83. I did have Corsa exhaust on it before that, and imagine it added a few hp, but that was the only thing I did over stock. These cams have the 4* insert for the VVT.
After it was tuned for 91 and run on the dyno it picked up around 30 hp. I'm happy with that. Just the faintest idle lope but still great for a DD, and my mpg if anything increased a little bit under normal driving.
What year truck? If it has the vacuum pump, now the is perfect time to ditch that too.
I did do some extras like injectors and the HPFP only because I was there and it seemed like a good time to do it with 140k.

 

[intergalactron]

FWIW, when I did my delete recently I went with a BTR Stage 1 for my 2017 Yukon, L83. I did have Corsa exhaust on it before that, and imagine it added a few hp, but that was the only thing I did over stock. These cams have the 4* insert for the VVT.
After it was tuned for 91 and run on the dyno it picked up around 30 hp. I'm happy with that. Just the faintest idle lope but still great for a DD, and my mpg if anything increased a little bit under normal driving.
What year truck? If it has the vacuum pump, now the is perfect time to ditch that too.
I did do some extras like injectors and the HPFP only because I was there and it seemed like a good time to do it with 140k.

Mine is a 2020.

What vacuum pump do you speak of?

 

[intergalactron]

Got a report back from the machine shop. Only machining that needs to be done is honing the cylinders. Lifter bore from the collapsed lifter is good, the reason the lifter wouldn't come out is that the 'ears' on either side of the roller splayed out a bit when it failed. Main bearings are good (going to re-use), cam bearings are good (going to re-use). Rod bearings are going to be replaced, there were a couple with scratches. Crank doesn't even need to be polished. All in all, I got off pretty easy.

 

[2017sltXL]

Mine is a 2020.

What vacuum pump do you speak of?

The vacuum pump for the brakes. They probably quit doing them by 2020. It was there for those times when the DOD kicked in, and provided some additional vacuum for the brake booster. You would have known it was there when you took the engine out. They are more of a PITA than anything else.

 

[intergalactron]

The vacuum pump for the brakes. They probably quit doing them by 2020. It was there for those times when the DOD kicked in, and provided some additional vacuum for the brake booster. You would have known it was there when you took the engine out. They are more of a PITA than anything else.

Brakes are hydraulic. No vacuum pump.

 

[2017sltXL]

Brakes are hydraulic. No vacuum pump.

Well aware lol, was just curious if yours had it. They didn't run this pump for that many years but yours obviously didn't have one or you would have seen it hanging off the engine.