Ls swap

[Tommyups]

I’m going to be doing an LS swap in the very near future, my mechanic at work is going to do all the work, I’m more of a bolt on mechanic. Most likely will go with a 4.8 or a 5.3 depending on what we can find. The truck will not be an every day driver but probably close to it through the nice months. I’d like to have a nice cruiser with plenty of power and a subtle cool sounding exhaust. Our tentative plans are to go with… Automatic transmission, power steering, mild cam,vintage air and Total re-wiring of truck. I do have a four-speed right now so I will be getting a new steering column. Also I do have power brakes already. Any other ideas or input on my existing plans would be appreciated.

[BigBird05]

Go with the 5.3 or a 6.0. The 4.8 is a different platform.

[indymachinist]

There is an LS swap section for this kind of stuff.

Some will hate on the 4.8/5.3 and say why not go 6.0 blah blah blah. I don't get that. The 6.0 is not worth the price premium in my opinion.

You're going to have to make decisions on what exactly you want to do with the ls engine. There are a million cam options for LS engines and they take VERY well to cam swaps. There are lumpy sounding cams available that give you the sound you want but are still friendly to stock low rpm torque converters if that is what you are interested in.

As for wiring... I bought a universal Painless wiring harness. If I had it to do over again I would buy an American Autowire truck specific harness. It would be worth the extra money for the ease IMO.

With thr steering column only buy the good ones. Rebuilt OEM, modifiedvan tilt, Ididit, Flaming River. The rest are cheap chinese junk that no one should be using.

[indymachinist]

Originally Posted by BigBird05

Go with the 5.3 or a 6.0. The 4.8 is a different platform.

No it isn't. The 4.8 is nearly the exact same engine as the 5.3 with a shorter stroke crankshaft.

[Davidf]

I just finished an LS swap into my 71 Cheyenne. Yes, visit the LS Swap forums as there is a wealth of information there. I chose to go with the ubiquitous 5.3L as they are plentiful (I think mine is a 2003). At nearly 300 HP, it has plenty of get up and go...my truck is FAST with right now acceleration. Remember, our trucks are much lighter than the trucks the Vortec was intended for. And, I agree, the 4.8 is essentially the same block/architecture/platform. The only difference is stroke and pistons (flat tops on the 4.8, dished on the 5.3. Pistons are really the only way you tell the two engine apart as the block is stamped 4.8/5.3). Unless you want to really smoke the tires, why bother with a hotter cam...stock configuration is plenty quick.

A "bolt on" mechanic can do the work especially if you stay away from custom work...like building a mount to reuse the LS air filter box, etc.

Also, I used Hooker Blackheart engine stands and trans crossmember. This setup uses F body engine mounts, but buy the urethan mounts as the rubber mounts will settle over time and cause the truck oil pan to rub on the steering link. The Hooker parts positions the engine low and allows the use of the LS a/c compressor without any modifications. But, to maintain driveline angles (long bed), you need to rotate the pinion shaft down with 4 degree shims (assuming you go one piece driveshaft).

Don't buy a Painless yet. If you mechanic is any good, he will reuse the donor wiring harness and most of the C10 under hood wiring will go away anyway. I used the C10 starter circuit and lighting circuits...MOST everything else was removed.

And, I put the HP fuel pump in the stock, in cab, fuel tank (look for my thread). If you do this, it is a must to wrap the tank in sound deadening or the noise will drive you crazy.

[LS short box]

My .02 on LS swaps no matter what they go in.
I buy the aftermarket LS harness and computer from one supplier so if there is an issue I have one company to talk to. I've used Speartech and Howell with good success.
A 24 tooth reluctor LS engines needs one ecm to run the engine and auto trans. 58 tooth engines need two ecm's, one for the engine and one for the auto trans.
I would do a 5.3 and run a small cam. New push rods and springs.
Not many low mileage 2003 5.3's around. If you buy a higher mileage 5.3 I would do a new oil pump, timing chain and new rear main seal. Make sure you compression test it before buying and pull a valve cover to see if it's clean or full of burnt oil. On my C10 swap I used a fbody oil pan so it didn't hang below the frame cross member.
I used a Ididit column and it worked well.
I used a Painless chassis harness. Worked well. I hate 50 plus year old wiring. LS swaps like and need nice 12 volt signals to work well. Also don't skimp on good grounds.
I like to run the biggest radiator I can fit. I used a Afco LS swap radiator and Spal 16" fan.
If you are running a stock 5.3 I would do a mail order tune. If the 5.3 has some mods I have it tuned on a chassis dyno.
Again just my .02. Good luck with your swap.

[Tommyups]

Thanks for all the great information. I definitely like the idea of keeping my same tank, I love the unique gas filler location of these old trucks. My mechanic that is doing the work is pretty sharp, he did say he could use the existing harness and make it work. That’s good information on just using the stock cam. That was one of my bigger questions I’ve been thinking about, what kind of engine mods if any I need to think about.

[Joemomma1]

Get whatever engine is available to you at the price you like. I do not see any value in the 6.0 with the premium on them. They are romanticized like crazy. Take the savings and put it elsewhere. New engine harness and ecm is cool but unnecessary. I used a BP engine harness; its a quality replacement. I used AAW for the truck harness, also a quality product. Aftermarket column is much simpler than trying to modify old parts to fit. Beware of the fools constantly crapping on china parts from their chinese phones and driving trucks with chinese reproduction parts, they're deluded.

[Accelo]

When doing a LS conversion you can save a ton of $ by using the stock location on the fuel tank. The saving can be $1 to 2K. Tank, wiring, fuel pump, filler tube and lines are all expensive. IMHO, Stay with the stock fuel tank and add a pump and call it good.
If you do go with the rear tank purchase a domestic tank by a reputable manufacture. You will save in the long run. Don't ask how I know.

[indymachinist]

Originally Posted by Joemomma1

Get whatever engine is available to you at the price you like. I do not see any value in the 6.0 with the premium on them. They are romanticized like crazy. Take the savings and put it elsewhere. New engine harness and ecm is cool but unnecessary. I used a BP engine harness; its a quality replacement. I used AAW for the truck harness, also a quality product. Aftermarket column is much simpler than trying to modify old parts to fit. Beware of the fools constantly crapping on china parts from their chinese phones and driving trucks with chinese reproduction parts, they're deluded.

I begrudgingly use China parts here and there where it makes sense (hello VS Racing turbos.)

China steering columns have been proven time and time again to be junk. I do hope you are not being a fool, suggesting using a potentially dangerous steering column.

[diggerbob]

Originally Posted by Accelo

When doing a LS conversion you can save a ton of $ by using the stock location on the fuel tank. The saving can be $1 to 2K. Tank, wiring, fuel pump, filler tube and lines are all expensive. IMHO, Stay with the stock fuel tank and add a pump and call it good.
If you do go with the rear tank purchase a domestic tank by a reputable manufacture. You will save in the long run. Don't ask how I know.

What electric pump should you use in a cab mounted tank so that you don't hear the noise of the pump running?

[Accelo]

I would use a remote pump mounted under the cab. Many come with rubber mounts to assist in noise control. I know they make a pump for the inside of the tank. Just seems their would be no getting away from the noise. Covering the tank with foam and carpet would help if you had to put it there. Others that have used a "in tank pump" should chime in here as I have no experience with them on tanks in the cab.

[nsb29]

No replacement for displacement I have a 6.0 with a 6L80 E from a Pontiac G8 360 horse 380 foot pounds of torque stock in my 65 I will put it up against a stock 5.3 or a 4.7 any day I also run an intake fuel pump and the only time I hear it is when I first turn the ignition on they run cooler and last longer