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450HP 5.3l for a 1999 Silverado

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Old 05-15-2018, 07:20 AM
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Default 450HP 5.3l for a 1999 Silverado

First time poster and first time LS build. Wanting to keep cost down like everyone else because I'm a cheap @#$. Bought an LM7 from a newer Silverado to build and swap into my 1999 Silverado. Want to keep it NA. Need some brands and suggestions. Don't want to judge performance by price. Want between 400 to 500 HP. Was thinking LS6 heads but besides that I'm open for suggestions

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Old 05-15-2018, 07:30 AM
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LS6 heads will lower compression and you'll lose power.

500 HP N/A isn't going to be cheap. 400 HP N/A is much easier. Large cam, gen 4 truck intake, milled heads, long tubes, good tune will get you 400 HP no problem.
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Old 05-15-2018, 07:44 AM
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What vehicles did the Gen 4 intake come on. I wanted to go with that rather than a welded intake for cost efficiency. Also what would be a good cam to go with. Nothing to aggressive because it will still be a daily. Just need more power to haul my tractors with
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Old 05-15-2018, 08:08 AM
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Any 08+ truck with a 4.8/5.3.

Mild cam. 215-225 intake duration, and around 218-228 exhaust duration. Lower will make more torque, higher will make more power. Keep the LSA around 112.
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Old 05-15-2018, 08:16 AM
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Originally Posted by Kooper21 View Post
First time poster and first time LS build. Wanting to keep cost down like everyone else because I'm a cheap @#$. Bought an LM7 from a newer Silverado to build and swap into my 1999 Silverado. Want to keep it NA. Need some brands and suggestions. Don't want to judge performance by price. Want between 400 to 500 HP. Was thinking LS6 heads but besides that I'm open for suggestions
To be fair its going to extremely hard to hit those numbers NA on a budget. First thing is always to figure out what you want the truck to do daily driver? All out race car? Weekend warrior? then plan your build around that. A 6.0 would be a little easier to get closer to the numbers you are asking with aftermarket heads fast intake and cam. Also are you planning to put a stall in this truck that's going to eat up allot of you power on the rollers.

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Old 05-15-2018, 08:22 AM
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To be fair, he never said the power rating was at the wheels.
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Old 05-15-2018, 08:28 AM
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Originally Posted by JoeNova View Post
To be fair, he never said the power rating was at the wheels.
That's true I guess I was just assuming since I rarely ever see anyone reference crank HP.
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Old 05-15-2018, 10:26 AM
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You can build a ls3 making roughly 600hp at the crank NA with just heads cam, intake and exhaust
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Old 05-15-2018, 10:45 AM
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Originally Posted by Pvfdpinky View Post
You can build a ls3 making roughly 600hp at the crank NA with just heads cam, intake and exhaust
Doesn't really fit the 'budget build'. Someone could've wondered in here and said you can do 700 HP with the same on an LS7. It doesn't matter.
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Old 05-15-2018, 10:51 AM
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Originally Posted by JoeNova View Post
Doesn't really fit the 'budget build'. Someone could've wondered in here and said you can do 700 HP with the same on an LS7. It doesn't matter.
To be fair he never really stated what the "Budget was".............................
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Old 05-15-2018, 11:05 AM
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Everyone's "budget build" is different, a low mileage(under 100,000 miles) with transmission can be had for $7,000. But for the 5.3 make it a 383 stroker with tfs genx 215 heads, fast lsxr intake with 102mm TB and a decent cam and tune would be low 500 at the crank
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Old 05-15-2018, 11:13 AM
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Originally Posted by Pvfdpinky View Post
Everyone's "budget build" is different, a low mileage(under 100,000 miles) with transmission can be had for $7,000. But for the 5.3 make it a 383 stroker with tfs genx 215 heads, fast lsxr intake with 102mm TB and a decent cam and tune would be low 500 at the crank
Stock 5.3 long block with LS6 springs and a home built $800 turbo setup will make more than either the N/A LS3 or 383 stroker for 20% of the budget.

Irrelevance is irrelevance. Something tells me that when he says he's a cheap ***, that doesn't mean he's ready to drop 7k on an engine.
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Old 05-15-2018, 12:16 PM
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Thank you all for the great information. I think what I am going to do is lower my goal for HP for 400-450. I'll go with the intake manifold from a gen 4 found one on eBay for 100$. Looking at Wiseco Forged Pistons. Most likely a mild Comp Cam. Thinking maybe rather than the LS6 heads just porting stock heads to increase air flow. And obviously larger exhaust. Stock just seems too restrictive
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Old 05-15-2018, 12:19 PM
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Forged pistons for 400 HP? Save your money.
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Old 05-15-2018, 12:23 PM
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I've heard of issues with ring gap at higher rpm. Is that something I should be concerned with. The rings need replaced anyway because they have some oil leak down
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Old 05-15-2018, 12:39 PM
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Re-ringing is your choice, but forged pistons is a poor one.
Get some 4.8 pistons. You can probably score them for $50. They'll offer almost a whole point compression bump on a 5.3. Couple with some .040" thick head gaskets and you'll have 10.8:1 compression.
Grab some new OEM rings.

You can keep it simple and get LS6 springs and the Howard's version of the GM Hot Cam ($400 for cam and springs). $250 for Speed Engineering long tubes to fit your 99.

You're looking at $1000 in parts for a solid 425 HP combo that makes excellent torque. It'll have to run on 93 with that much compression.


One thing I noticed that confuses me. What do you mean you got an LM7 out of a newer Silverado? The LM7 stopped production in 07. The 99 you have came equipped with an LM7.
What year/engine did you actually get?
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Old 05-15-2018, 12:48 PM
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The 5.3l that we are swapping into it is from a 2008. Wasn't 100% on the engine code if you could enlighten me
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Old 05-15-2018, 12:50 PM
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Originally Posted by Kooper21 View Post
The 5.3l that we are swapping into it is from a 2008. Wasn't 100% on the engine code if you could enlighten me
Are you sure it doesn't already have 243 heads on it?
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Old 05-15-2018, 12:57 PM
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Then its a Gen 4. That changes things significantly. It'll likely have either VVT or DoD. Both should be deleted.
You'll have to get a separate trans controller if you're using an auto trans from the 99, the gen 4 ECU didn't do trans control like the earlier ones did.
The Gen 4 also only did electronic drive-by-wire throttle, and weren't compatible with traditional cable throttle.
It should already have a Gen 4 intake, LS6 style heads, and flat top pistons ~ 9.9:1 compression (slightly less with VVT), so its not a bad start.

If you want to bypass the electronics issues, you can get a Lingenfelter 24x conversion box to run a gen 3 PCM that will do trans control.
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Old 05-15-2018, 01:13 PM
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That was a typo. It's a 2005. Is that still a gen 4? And we have a set of LS6 heads. Would I be better off getting the components from the ls6 heads and installing them to the stock heads? Or would I be better off porting the stock heads and going from there
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