I will be swapping in a 5.3L and I have a question

[Ben_Olddermin]

Any 5.3L people around here? I will soon have to replace my tired old 350. The piston rings have died. I came across a very good deal on a 2005 donor truck for the 5.3L conversion so I jumped on it.

My question is this. What can be done to squeeze a little more power from the 5.3L without tanking the fuel mileage? Before anyone says it's impossible think about a full exhaust system. Long tubes and everything else. That would of course give you more power, (though not much) and it wouldn't harm the MPG. Converting to an electric fan has also been known to help.

So now you see what I am saying. What else is there?

Thank you

[peewee0413]

Any 5.3L people around here? I will soon have to replace my tired old 350. The piston rings have died. I came across a very good deal on a 2005 donor truck for the 5.3L conversion so I jumped on it.

My question is this. What can be done to squeeze a little more power from the 5.3L without tanking the fuel mileage? Before anyone says it's impossible think about a full exhaust system. Long tubes and everything else. That would of course give you more power, (though not much) and it wouldn't harm the MPG. Converting to an electric fan has also been known to help.

So now you see what I am saying. What else is there?

Thank you

More power good fuel mileage... can be hard to achieve...remove the cat, put free flowing exhaust add headers. Most don't like  going to a 5.3.. do some vortec style heads threaded rocker studs little better cam roller rockers are said to gain up to 20 hp. maybe depending on what your budget is. The head and intake can be bought used modified or new kit. Compression is good but too high and you'll need premium fuel. Hard question to answer... You could retro roller cam and increase injector size, get a chip. There's TBI mods that help a little, but ultimately the stock TBI is like 500cfm. I almost opted to do a stock TBI and chip for my 93 1500 to work with.  Wouldve been way more effort than the bolt on stuff I did. Decided to go full build Aftermarket EFI, chose the cam and compression I wanted, gutted the computer put a Performabuilt transmission in(after two smoked from the HP increase) and a US Shift quick 4 tranny controller. Best 10k I ever spent. Lol I can't go 75% throttle without roasting the tires....gotta put a Yukon posi in soon. Wanna go from 3.42 to 4.10. Of course everything I did was the opposite of fuel economy. I get 9 mpg all day long. 12 if I run the crap tune on my tranny and EFI. The truth is GM choked the crap out of those engines, and it takes a lot to get em to breath and run good...

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[peewee0413]

https://youtu.be/73M6_cMi79U

This is after the cam break in
 Idle was still at 950 before adjusting it to 850. I think I'm going to go to 800 or 750, but it makes my tranny controller throw a TPS fault..Will take some tweaking.

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[peewee0413]

I didn't originally gut the ECU, but this is when I added an MSD adjustable rotor and started gutting the computer and all its wiring. Anyone putting a fitech in needs to put an adjustable rotor when using timing control ...majorcl improvements when done Removed the cruise control,  no AC. Put two tranny coolers in the condensers place. My $3500 transmission is more important than AC.

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[ehjorten]

Not sure what peewee is going on about. Your 2005 LS 5.3l is rated at about 295 HP at 5,200 RPM and 335 lb·ft @ 4,000 RPM. It definitely doesn't have a TBI. Your biggest bang for the buck I think is a cam swap to waken up these engines. It is pretty easy to get 400 HP out of them with even a mild cam swap. Your best bet for fuel economy is to keep the fuel injection.

[Ben_Olddermin]

Not sure what peewee is going on about. Your 2005 LS 5.3l is rated at about 295 HP at 5,200 RPM and 335 lb·ft @ 4,000 RPM. It definitely doesn't have a TBI. Your biggest bang for the buck I think is a cam swap to waken up these engines. It is pretty easy to get 400 HP out of them with even a mild cam swap. Your best bet for fuel economy is to keep the fuel injection.

I will definitely be keeping the fuel injection. Do you think that the mild cam will affect MPG much? Or road manners?

[peewee0413]

Not sure what peewee is going on about. Your 2005 LS 5.3l is rated at about 295 HP at 5,200 RPM and 335 lb·ft @ 4,000 RPM. It definitely doesn't have a TBI. Your biggest bang for the buck I think is a cam swap to waken up these engines. It is pretty easy to get 400 HP out of them with even a mild cam swap. Your best bet for fuel economy is to keep the fuel injection.

I'm thinking gen1 TBI....don't mind me, I'll sit back down.. You know the forum doesn't say LS, so I got a little confused...

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[JohnnyPopper]

Ditch the gunther fan and go electric, instant increase in power.

[ehjorten]

What are you putting it into? I can't imagine that a tired, old 350 would get you very good fuel mileage. The 5.3 l engine in a 2005 1500 Silverado got like 16 MPG. There is a lot of information on cam swaps on the interwebs on the 5.3 l. For a truck, I would avoid the LS7 or LS9 cam swap. Those add good HP, but at the sacrifice of low and mid-range torque. You might just be happy with the 5.3 l and some mild add-ons, like headers and electric fans. You can also get a tune (I am assuming you aren't tuning yourself).

[Mr Diesel]

I'm curious what kind of mpg you think you will get and what size truck it's going into. I have a 1989 V3500 4wd that needs a new engine and I've been toying with the idea of 5.3.

[Ben_Olddermin]

What are you putting it into? I can't imagine that a tired, old 350 would get you very good fuel mileage. The 5.3 l engine in a 2005 1500 Silverado got like 16 MPG. There is a lot of information on cam swaps on the interwebs on the 5.3 l. For a truck, I would avoid the LS7 or LS9 cam swap. Those add good HP, but at the sacrifice of low and mid-range torque. You might just be happy with the 5.3 l and some mild add-ons, like headers and electric fans. You can also get a tune (I am assuming you aren't tuning yourself).

It will go into a 1987 long bed. Sticker says it weighs 4500 lbs so maybe there will be a small increase. But I'm under no illusions it that MPG will actually increase. Who knows maybe it will decrease. I just wanted to give it a little help if I can. Because why not. . while I have it all apart. I'm gonna be in there anyway so now is the time. Yes mild is what I am looking for. So I will also add an aluminum driveshaft.

I was just hoping to find every little trick like that. Maybe there is something to be gained by a lighter flywheel.

I'm curious what kind of mpg you think you will get and what size truck it's going into. I have a 1989 V3500 4wd that needs a new engine and I've been toying with the idea of 5.3.

Normally I kind of doubt there will be much of an increase in MPG when going from the 350 to the 5.3L. IF my 350 was new. Since it's from 1987 and is worn out, maybe I'll get a 1 or 2 MPG increase since the 5.3L has only 90k on the clock. I also got the service records from before the wreck, and they did good maintenance on the donor truck. I'm hoping the 5.3L it will make it to 350k miles, so I don't want to add a lot of power. Just a little. Sounds like the factory cam may be the way to go. I don't want to lose low and midrange torque.

For your purposes it sounds like you might want a 6.0 or even the 6.2L. The difference between a 5.3 and a 6.0 seems to be about 41 cubic inches. Not much else. I think even the block is the same. But it looks like those 41 ci gives 30 more hp. You probably want that for the big heavy dually. Unless you are planning some power mods. Then it may not matter because the 5.3L has a strong bottom end and can take a ton of mods and doesn't care.

[JohnnyPopper]

Why not use an RV cam grind?

As for the flywheel, not a good idea. That's where your kinetic energy is stored. 

[Ben_Olddermin]

Why not use an RV cam grind?

As for the flywheel, not a good idea. That's where your kinetic energy is stored.

That reminds me of the transmission debate. Some say 4l60e is no good and will die sooner. Others say to build one of those up instead of using 4l80e. Because the 4l80e is tougher but that comes at the cost of needing more power. I'll go with 4l80e and skip all the problems.