Mod planning

[Jobi-Wan Kenobi]

Alright, help me chart a path here guys.

A little background. Yesterday after work I was crawling around under my hood looking for an oil leak since my engine has been kinda slobbering on itself and seemingly dripping a bit onto the exhaust (thinking valve cover gaskets right now). I noticed two broken exhaust manifold bolts on the drivers side (front and rear most) so started thinking that this may be a good time for exhaust upgrades. Today now I looked at the passenger side and the manifold is actually split right in the middle on the flange and looks like its been that way for a while. So I have more justification now for upgrades.

Here's where I'm at now. I know I can buy different style headers or stick with a stock exhaust manifold. I wouldn't mind squeezing a bit extra power out. But this vehicle is also a daily driver so not looking to go crazy. And completely understand that the transmission is likely going to need some work since they don't seem like much power over stock. Regarding exhaust headers, shorties seem like an good upgrade since they would fit in place of the stock manifolds. Long tubes would be better performing but won't be a drop in replacement. I'd do a tune at some point. Maybe a cam swap. And probably not much more than that.

What kind of experience have you guys had here? What have you done with your vehicles?

 

[Marky Dissod]

My previous experiences are with mid-'90s LT1 Caprices / RoadMasters / Fleetwoods. Even so ...

Thinking about a cam swap or better heads - whichever is cheaper? or whichever is a better bang for the buck?
OE exhaust manifolds don't do well over the OE engines' OE redline. (The apostrophe is EXACTLY where it belongs.)
The OE exhaust manifolds are the major reason why 4.8L & the 5.3L & the 6.0L all share similar redlines.
If you're gonna do a cam swap, seriously think about upgrading the OE manifolds.

Same / Above goes for 'shorty' headers that keep the catalytic converters in the OE location.
If you want the engine to breathe better at highER RpM, OE manifolds / shorty headers are a compromise at best.

You should already have done a tune, even if you'll eventually need another. The difference is that big.
(Goes for literally ANYONE who owns a vehicle with a GM V8, damnit; people really don't know what they're missing.)

But for all my experience modding mid-'90s GM LT1 V8s, I regret not improving the suspension further.
Already got tuned.
Before I do any more engine mods - yes, out of fear of needing a 4L60E rebuild - I'll get more bang - and SPEED - for my buck improving the ride / handling balance with better swaybars / shocks / springs, than by modding the engine.

Traffic is just too freakin' dense in NYC. More horsepower is less useful than better handling.

 

[Fless]

I noticed two broken exhaust manifold bolts on the drivers side (front and rear most) so started thinking that this may be a good time for exhaust upgrades. Today now I looked at the passenger side and the manifold is actually split right in the middle on the flange and looks like its been that way for a while. So I have more justification now for upgrades.

Got news for you, they're made with the split. Not tryin' to ruin your justification, though.

 

[Jobi-Wan Kenobi]

Got news for you, they're made with the split. Not tryin' to ruin your justification, though.

View attachment 405955

Well look at that . I guess this isn't as serious as I was thinking then. Still got broken manifold bolts but since I couldn't see a split on drivers side I figured something was wrong with the passenger side.

 

[Jobi-Wan Kenobi]

My previous experiences are with mid-'90s LT1 Caprices / RoadMasters / Fleetwoods. Even so ...

Thinking about a cam swap or better heads - whichever is cheaper? or whichever is a better bang for the buck?
OE exhaust manifolds don't do well over the OE engines' OE redline. (The apostrophe is EXACTLY where it belongs.)
The OE exhaust manifolds are the major reason why 4.8L & the 5.3L & the 6.0L all share similar redlines.
If you're gonna do a cam swap, seriously think about upgrading the OE manifolds.

Same / Above goes for 'shorty' headers that keep the catalytic converters in the OE location.
If you want the engine to breathe better at highER RpM, OE manifolds / shorty headers are a compromise at best.

You should already have done a tune, even if you'll eventually need another. The difference is that big.
(Goes for literally ANYONE who owns a vehicle with a GM V8, damnit; people really don't know what they're missing.)

But for all my experience modding mid-'90s GM LT1 V8s, I regret not improving the suspension further.
Already got tuned.
Before I do any more engine mods - yes, out of fear of needing a 4L60E rebuild - I'll get more bang - and SPEED - for my buck improving the ride / handling balance with better swaybars / shocks / springs, than by modding the engine.

Traffic is just too freakin' dense in NYC. More horsepower is less useful than better handling.

If I did do a cam swap its something thats going to be farther off in the future. Not sure when that would actually happen since I've been focused more on fixing other issues with it that show up (I've had it home and driving it for a little over a month now). The tune is something I want to do but haven't had a chance to figure out what I actually want yet. Handling aspects are something else I want to get into with it as well.

 

[iamdub]

Alright, help me chart a path here guys.

A little background. Yesterday after work I was crawling around under my hood looking for an oil leak since my engine has been kinda slobbering on itself and seemingly dripping a bit onto the exhaust (thinking valve cover gaskets right now). I noticed two broken exhaust manifold bolts on the drivers side (front and rear most) so started thinking that this may be a good time for exhaust upgrades. Today now I looked at the passenger side and the manifold is actually split right in the middle on the flange and looks like its been that way for a while. So I have more justification now for upgrades.

Here's where I'm at now. I know I can buy different style headers or stick with a stock exhaust manifold. I wouldn't mind squeezing a bit extra power out. But this vehicle is also a daily driver so not looking to go crazy. And completely understand that the transmission is likely going to need some work since they don't seem like much power over stock. Regarding exhaust headers, shorties seem like an good upgrade since they would fit in place of the stock manifolds. Long tubes would be better performing but won't be a drop in replacement. I'd do a tune at some point. Maybe a cam swap. And probably not much more than that.

What kind of experience have you guys had here? What have you done with your vehicles?

Best bang-for-the-buck is a GOOD tune. You'll get more responsive operation, more power at the wheels and possibly prolong the life of your trans. Headers, etc. aren't worth it if doing alone. They're better as a supporting mod for major engine upgrades such as cam and/or head work.

Optimize what you have now by ensuring all the stock points are up-to-par (spark plugs, fluids, filters, sensors operating properly, etc.). Tune it for optimal operating efficiency. When this gets old and you're ready for more, might I suggest a NNBS intake manifold swap? This will be a feel-able mod that will support bigger future mods.

 

[Jobi-Wan Kenobi]

Best bang-for-the-buck is a GOOD tune. You'll get more responsive operation, more power at the wheels and possibly prolong the life of your trans. Headers, etc. aren't worth it if doing alone. They're better as a supporting mod for major engine upgrades such as cam and/or head work.

Optimize what you have now by ensuring all the stock points are up-to-par (spark plugs, fluids, filters, sensors operating properly, etc.). Tune it for optimal operating efficiency. When this gets old and you're ready for more, might I suggest a NNBS intake manifold swap? This will be a feel-able mod that will support bigger future mods.

So there isn't much of a benefit to doing headers unless I were to do cam? Since that's something that may not happen for a while if it even does I'm probably better off then keeping stock manifolds.

The tune I do want to do here at some point. That intake swap is definitely intriguing though.

 

[iamdub]

So there isn't much of a benefit to doing headers unless I were to do cam? Since that's something that may not happen for a while if it even does I'm probably better off then keeping stock manifolds.

The tune I do want to do here at some point. That intake swap is definitely intriguing though.

Long tubes... Sure. But, if you're keeping cats then that's even more $$$. Shorties, alone, no. You can do a larger Y-pipe (will have to have one made) to complement the shorties. Either long tubes or shorties really need to be coated as the extra heat they radiate will rot harness loom and, if your intake filter box isn't well-sealed, negate any gains they may yield.

Still, with the cost to do it right, a tune would be cheaper and have a better return on investment. Also, headers would be best optimized by a tune.

For now, enjoy the lower engine bay temps, not hearing exhaust pinging sounds and having cats so your exhaust doesn't stink up your clothes.

 

[Mudsport96]

Header dyno results on a 4.8

On an engine dyno with no accessories so numbers will seem high.
Shorties are not worth the time or effort spent..
And even long tunes aren't worth it in my opinion ( for a stock cammed engine).

Follow this guy's channel he has just about every test you can imagine for a 5.3.

 

[mountie]

Interesting read........ ( long ago, I spoke with my friend, Doug Thorley ( Thorley Headers)..... He said, unless you are highly modifying your engine, after market headers are a waste of money).

Anyway..... You people suggest a "tune". My '05 Yukon 5.3 runs... fine...... But is there a 'Black Bear tune" that just improves my performance a little better? I don't drive it like a hot rod. But a little better 'launch' would be nice. ( worth the cost?)

 

[Marky Dissod]

Any thorough GMT800 pcm tune (including but not limited to BlackBear) should quicken engine AND transmission throttle responses.
Unless your tune specifies 91 or 93 octane 'only', the transmission improvements will likely be more obvious than the engine improvements. That doesn't make the engine improvements less important though.
Tunes tend to work better with electrical fans.

 

[iamdub]

Interesting read........ ( long ago, I spoke with my friend, Doug Thorley ( Thorley Headers)..... He said, unless you are highly modifying your engine, after market headers are a waste of money).

I have his Tri-Ys on my Tahoe. I don't know if the mild-moderate cam is enough modification to justify the headers. But, I like the way it runs so they'll stay until I'm ready to turbo it.

Anyway..... You people suggest a "tune". My '05 Yukon 5.3 runs... fine...... But is there a 'Black Bear tune" that just improves my performance a little better? I don't drive it like a hot rod. But a little better 'launch' would be nice. ( worth the cost?)

There's a decent amount GM left on the table just with getting the power the engine already makes to the wheels. The throttle response is lacking, too. This, coupled with relatively soft and squishy transmission operation (read: "slip"), leads to a lazy feel and reduced usable power. The engine is making/can make X power, but an unnecessary amount of it is lost in trans slip or reduced timing. This is to favor operating comfort but it's at the expense of clutch life and driving response. Black Bear pretty much has it down to a science on cleaning all of this up. The extra power at the wheels is more of a side benefit, but desirable nonetheless. The engine is still operating well within its means. They can tune for more power on all octane levels if you do want more power from the engine itself.

 

[adriver]

First, don't bother with a CAI. It's a waste of money. While saying that, so do TB spacers.

It's really going to depend on your budget and goals.

Tuning needs to be a part of whatever you do: ~$500 to do it yourself, ~$500 to have someone do it for you once, ~+$1K to get something that will keep doing it for you.

An exhaust is going to be needed. I will argue with everyone on here about this one, and I can at least tell you from personal experience, that the single biggest problem with our exhaust system is the collector at the cats. Your cats go from dual 2 1/2 to single 3" (might even be smaller). That's a 3/4" reduction in size. Have you ever floored it, and after 4500 it starts to accelerate slower. That reduced acceleration is because of the restriction your exhaust is experiencing because of that collector.
Long tubes move or remove the cats. You can run an x-pipe or straight back exhaust, requiring an entirely new exhaust.
Short tube headers DO IMPROVE FLOW, but they won't do it alone, and they won't do it unless you remove that collector restriction. If you just want sound you can change the muffler, and I wouldn't bother with anything else. If you want improved performance, you need to remove that collector and not have a choke point in your exhaust. If you can weld, you can do a dual 2 1/2 to 3 1/2" collector with a custom made 3 1/2 exhaust back, or dual 2 1/2 back. Short tubes will let you do it in sections too, unlike long tubes where you need to build it all at once to have a complete exhaust. Shorties are legal, some even in CA. No long tubes are street legal on an NBS.

(THE REASON PEOPLE ON HERE THINK SHORTIES DON'T DO ANYTHING - Is because when you do long tubes, you ALSO remove that collector. Shorties alone don't change anything about the only choke point you have).

To keep it semi mild - (NOT FI)
Cam, and can do intake. If you want a little more after that, then heads. Beyond that, You need to research through other sections of the forum, and spend 1-2 times what the SUV is worth if you want it to be able to control that power.

 

[Mudsport96]

Have you ever floored it, and after 4500 it starts to accelerate slower. That reduced acceleration is because of the CAM BEING DESIGNED FOR A TRUCK therefore not making as much power up top.

There fixed it for you

(THE REASON PEOPLE ON HERE THINK SHORTIES DON'T DO ANYTHING - Is because when you do long tubes, you ALSO remove that collector. Shorties alone don't change anything about the only choke point you have).

Partially correct. Watch the Engine dyno video I posted previously. Shorties are worth at max 5 to 7 hp.... on a setup WITHOUT cats. The 3rd generation manifolds are so good they don't become a real restriction till close to 450hp.

To keep it semi mild - (NOT FI)
Cam, and can do intake. If you want a little more after that, then heads. Beyond that, You need to research through other sections of the forum, and spend 1-2 times what the SUV is worth if you want it to be able to control that power.

Truck intake manifold is good to almost 500 hp in a TRUCK application where you need low-end tq. It is literally better than the LS1 intake and almost as good as the LS6 intake manifold.
As for controlling it, do you mean computer? The stock computer is completely tunable for anything a tahoe needs.

 

[Marky Dissod]

THE REASON PEOPLE ON HERE THINK SHORTIES DON'T DO ANYTHING
is because when you do long tubes, you ALSO remove that collector.
Shorties alone don't change anything about the only choke point you have.

Is it possible to remove or upgrade the collector, independent of manifold / header choice?
Is it possible to remove or upgrade the collector while still using OE manifolds?

 

[Mudsport96]

Is it possible to remove or upgrade the collector, independent of manifold / header choice?
Is it possible to remove or upgrade the collector while still using OE manifolds?

He is talking about the y pipe. Yes you can. Get a factory 2500 suburban or pickup exhaust. It is larger than the 5.3 exhaust and possibly what the LQ9 Yukons have ( i haven't been under that fancy of a rig since i left the dealership). It is dual pipes all the way to the muffler.

 

[Mudsport96]

Factory intake test 549 hp


Factory 706 heads good for 513 hp.

 

[Marky Dissod]

He is talking about the y pipe. Yes you can. Get a factory 2500 suburban or pickup exhaust.
It is larger than the 5.3L exhaust and possibly what the LQ9 Yukons have.
( i haven't been under that fancy of a rig since i left the dealership).
It is dual pipes all the way to the muffler.

So, I should look for a 2500 6.0L LQ4 / LQ9 GMT800 Y-pipe?

 

[Mudsport96]

So, I should look for a 2500 6.0L LQ4 / LQ9 GMT800 Y-pipe?

Yes. They even use the same ypipe as the 8.1 liter trucks. The only difference is that the first foot or so is different because the LS is obviously narrower than the 8.1.

Edit: the pipe size is the same just bent differently I should have specified better.

 

[adriver]

I really don't want to get into stupid arguments like this.

Header dyno results on a 4.8

On an engine dyno with no accessories so numbers will seem high.
Shorties are not worth the time or effort spent..
And even long tunes aren't worth it in my opinion ( for a stock cammed engine).

Follow this guy's channel he has just about every test you can imagine for a 5.3.

There fixed it for you

Partially correct. Watch the Engine dyno video I posted previously. Shorties are worth at max 5 to 7 hp.... on a setup WITHOUT cats. The 3rd generation manifolds are so good they don't become a real restriction till close to 450hp.

Truck intake manifold is good to almost 500 hp in a TRUCK application where you need low-end tq. It is literally better than the LS1 intake and almost as good as the LS6 intake manifold.
As for controlling it, do you mean computer? The stock computer is completely tunable for anything a tahoe needs.

You didn't need to fix anything. A stock 5.3 isn't revving high enough to drop off because of the stock cam.

and since you're basing this off of the video you posted, shorties on a stock engine picked up 4hp and 6lb ft, and illegal long tubes without cats, picked up SIX HP, AND 15 LB FT. So someone need to ask themself do they want to compromise, or do they want every little bit. This isn't about what you would do, this was the OP asking about a "drop in replacement, and a daily driver they want to squeeze a little more power out of".

truck intake helps, but capable does not mean ideal. Also, all the videos you're basing your knowledge and specs off of, are on a 6.0. LS1 intake has no reason to even ben mentioned in this thread, not sure why you would bring that up. "can do intake", it will help. OP needs to figure out a lot of things.

You're responding to me as if what I said was exactly what needs to be done, and not a quick answer to how to plan for their mods.


"Controlling it do you mean computer?"- What part of this wasn't clear?
Tuning needs to be a part of whatever you do: ~$500 to do it yourself, ~$500 to have someone do it for you once, ~+$1K to get something that will keep doing it for you.

This isn't a guide, this is BASIC IDEA of what they need to go learn, and can get a quick idea of what options they have.

Factory intake test 549 hp


Factory 706 heads good for 513 hp.

6.0.