Other reasons. Valve train noise. Reliability as higher lift cams will put more wear on other parts too.

 

I've got a fresh 6.0 but I don't tow that often and would like to stay somewhat close to 5.3 mpgs since it's my only way of going right now.

My exhaust is starting to fall apart is another reason why I was thinking about going ahead and doing headers and full exhaust.

I'm really trying to stay away from regearing right now.

It's also possible it might see some juice on rare occasion

Thanks for all the info so far!

 

I don't see why you wouldn't get just as good if not better mpg with the 6.0 seeing as it will make more torque

 

If you're in there to swap cams, go ahead and port your oil pump for a little more flow. The castings look like crap, and you can make a world of difference with a dremel. I had concerns with my junkyard 5.3 with 160k, so I ported the pump and shimmed the spring, which I do don't recommend. I had at least 60-80 psi at all times.... It was a bit much, so I'd just port the pump for more volume.

 

For towing you want tq a 5.3L is only going to get you so much tq due to the little amount of cubes.

Do NOT get ported heads are bigger valves. the stock ones will produce the most lowend tq possible for a 5.3L. However I would mill the S*** out of them to raise compression up. 0.03 milled with stock gaskets will get you around 10.1-2: compression. If you mill the heads you will need to get a push rod length checker to obtain the proper push rod length.

As for a cam I would go with the vinci 210/218 .551/.551 on a 116Lsa. This cam will increase your fuel millage 1-2 with and provide major low end tq with the 8* split duration.

Defiantly need new lifters and trays, timing chain, new oil pump since you have to pull it off to swap the chain anyways, all new gaskets and pro comp head studs $70, not a fan of expensive ARP for na motor

For the exhaust I would do wither a y pipe with 3" or a true dual 2.5" with H or X pipe to equal out the exhaust pressure.

With the cam I mentioned, headers/exhaust and a premium tune, you should see a solid 3-4 mpg increase with a stock stall.

Your 3.73 gears are perfect for towing/fuel millage, the 3.42s would be best for mpgs but not for towing, and a Z71 would mean changing out front and rear gears, not worth the money.

 

Excellent advice to build more low end in a 5.3 for improved towing keep the velocity up with small ports / valves plus compression makes torque ....keep the stock stall for serious towing ......I tow 7000lb enclosed with my 5.3 with similar mods

 

the higher lift cams will make power higher in the power range... not exactly optimal for towing also...

 

They make better power everywhere, biggest thing on where it occurs is the duration. You could put the 2.00/1.57 valves in and pick up torque and power as long as you don't port out the runners to 225cc like most of the places do, to keep the velocity up. The faster the valve gets into the biggest flow lifts, the better it will run, now I can accept the durability argument to a point, but even a high lift 212 cam is only what .550 lift? I have a 218/224 with .564/.581 lift in my 190k mile 5.3 and it's been in there the last 40k miles. It's made several trips back and forth across the state of Texas from one corner to the other averaging 80mph with my 18' trailer and several different cars in it. 3700rpm in drive for several hours at a time and the little 5.3 will still push the 5400lb truck to 90mph in the 1/4 at 5800'DA. It would really wake up with another point in compression, but until it quits, I'm just gonna run the crap out of it.

 

^yes on the valve part, and keeping the runners small, but I would just leave the stock heads alone except milling them, not worth the money to change valve size.

Same goes for the intake manifold and throttle body, just leave them stock. They will make the most low end tq over any intake manifold on the market. You could diy port the throttle body for a little more throttle response and a few hp up top

 

Sorry I haven't been able to check up on here. Thanks for all the awesome info 69camaro427.

So would running an tbss intake not be worth it vs the original one on the truck?