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Hello, new guy here currently building my first vehicle lm7 5.3 block and heads are at the machine shop just about everything is otherwise ready to go, I have read around a lot a lot for months but i’d like somebody who’s done this to give me some insight on what i’m about to build:
it’s an lm7 block probably not bored anything over stockish I think 3.78,
btr stage 2 turbo cam with .660 springs 7.4 rods
probably (once I know specific size from shop) weisco pistons, found a good crank cheap, btr rods
bosch 60lb injectors walbro 450 pump stock rails
stock truck intake
heads are 243
T70 T4 62mm turbo (chinese whirly bird cheap)
donor truck is a hydro locked v6 5 speed 2wd will prob get a t56 as cheap as I can and maybe a F body clutch to start.
on a real note, is this thing gonna be sweet or a bust ? longevity if done right, power, smiles per gallon ?
First thought: Your turbo is too small. If your goal is instant torque and a 4500 RPM redline, then sure, run it. But it's going to run out of breath quick. I'm building an LH6 5.3 turbo combo, and I'm going to be running a T4 .96 A/R VS Racing 78/75 billet, and I'd consider it a middle of the road turbo. Depending on power goals/fuel, 60 lb./hr injectors are on the small side as well. I'm planning on being able to run E85, so I'm going to run 120 lb./hr injectors. Your needs may be different, of course. 60 lb./hr injectors will support about 735 crank horsepower on gasoline at 80% duty cycle. A cammed 5.3 is going to hit that power number REAL quick with a turbo. And when you want more ( and let's be real, we'll always want more ), you'll have to upgrade them. That truck looks like a clean ride and should be awesome with a turbo 5.3 and a T-56. You should start a build thread!
First thought: Your turbo is too small. If your goal is instant torque and a 4500 RPM redline, then sure, run it. But it's going to run out of breath quick. I'm building an LH6 5.3 turbo combo, and I'm going to be running a T4 .96 A/R VS Racing 78/75 billet, and I'd consider it a middle of the road turbo. Depending on power goals/fuel, 60 lb./hr injectors are on the small side as well. I'm planning on being able to run E85, so I'm going to run 120 lb./hr injectors. Your needs may be different, of course. 60 lb./hr injectors will support about 735 crank horsepower on gasoline at 80% duty cycle. A cammed 5.3 is going to hit that power number REAL quick with a turbo. And when you want more ( and let's be real, we'll always want more ), you'll have to upgrade them. That truck looks like a clean ride and should be awesome with a turbo 5.3 and a T-56. You should start a build thread!
I have thought about making a build post but everybody and their brother has built one, I figured i’d be beating a dead horse ! i’ve contemplated if/when I decide to go bigger, but honestly i’m too concerned with it not being reliable to want to push it any higher. i’m hoping the build is as clean as it can be, and as reliable as it can be. lots of people say you can’t really daily something like this but if i can make it a daily that is reliable i’ll go smaller to maintain the drivability.
if and when I decide for a bigger turbo does anything else need to be changed ? turbo is a t4 so something a little bigger should just bolt up right ? thanks for the insight !
If you're sticking with a T4 turbo, you just have to make sure it has the same configuration as your present turbo. In other words, does it have a standard or V-band exhaust inlet/outlet? Same goes for the inlet/outlet on the compressor side. Most of the cheaper turbos are going to have a standard T4 inlet and a V-band outlet on the turbine side, and slip fit connections on the compressor side. The other thing to watch out for is divided turbine housings. When you step up to higher A/R ratios, a lot of times they'll have a divided inlet and a larger exhaust outlet. For example, my VS Racing turbo can be configured with either a .96 or a 1.25 A/R, but the latter has a divided inlet and a 4" V-band outlet, vs. the 3" outlet on the .96. This can cause fitment headaches if you are running a full exhaust, but not so much if you're just going to run a dump tube. In addition, larger turbos physically take up more space, so if your packaging is already tight, you may not be able to fit a larger turbo. I doubt you'll have that issue on your Silverado, however.
If you're sticking with a T4 turbo, you just have to make sure it has the same configuration as your present turbo. In other words, does it have a standard or V-band exhaust inlet/outlet? Same goes for the inlet/outlet on the compressor side. Most of the cheaper turbos are going to have a standard T4 inlet and a V-band outlet on the turbine side, and slip fit connections on the compressor side. The other thing to watch out for is divided turbine housings. When you step up to higher A/R ratios, a lot of times they'll have a divided inlet and a larger exhaust outlet. For example, my VS Racing turbo can be configured with either a .96 or a 1.25 A/R, but the latter has a divided inlet and a 4" V-band outlet, vs. the 3" outlet on the .96. This can cause fitment headaches if you are running a full exhaust, but not so much if you're just going to run a dump tube. In addition, larger turbos physically take up more space, so if your packaging is already tight, you may not be able to fit a larger turbo. I doubt you'll have that issue on your Silverado, however.
i’m building it in North Carolina but i’ll be heading home to New York after the end of the next crop season (fall time). from what i’ve read, truck will have to have hi flow cats to be able to be registered up there. zero issue running a turbo dump and no cats down here, New York is one of the worst places to live and register a vehicle
12-21-2022, 09:18 PM
lm7 turbo potential ? 
