I'm getting ready to build a 5.3 to replace the stock 4.8 that's in my daily driver 2000 GMC Sierra Ex-cab 2wd. It currently has 237,000 miles on it but gets real noisy in the valvetrain when I do any towing so I'm staying away from towing now till I get my new 5.3 in it.

I've been given a 4.8 short block for free and will be swapping out the crank/rods and pistons for a 5.3 crank/rods and new 4.8 flat top pistons. I'm going to put a freshened set of 799 or 243 heads with the OEM truck intake and TB. I want this to be a simple swap of my existing motor. Plug and play you could say. I do plan on putting some long tube headers on it right away also.

I plan on towing with this truck still which is usually at the heaviest a 3500lb car on an 18ft open steel trailer.

I'm looking for a cam that will give me plenty of low end torque but have a slight chop to the idle. You know, that slightly modified street car sound. 300rwhp would be great.

I would like to stick with beehive springs and have a motor that sounds good, pulls good but I wouldn't be afraid to take on a 500 mile trip.

My truck runs the stock sized tires but I changed the gears from a 3.42 to a 3.73 a few years ago with a limited slip unit. The trans is the stock 4L60E but was rebuilt with a new planentary and has a corvette servo so it shifts very solid from 1st to 2nd. What are your thoughts on this? With your recommendations what changes besides the obvious computer reprogramming would you recommend? TIA

 

Check it out!!
Awesome thread here.

https://ls1tech.com/forums/dynamometer-results-comparisons/1741621-cam-motion-5-3-drop-cam-results-41rwhp-22rwtq.html

 

You do understand reprogramming is mandatory, right?

 

That was the last comment in my thread.

 

Tusky beat me to it. Drop in cam by cam motion. Will work with stock valve train, wake up your torque curve. Good choice on the heads. You might gain even more with a slight mill of the heads. 5.3 heads are usually 62cc. 243 are 64cc. Compression is always good

 

That is what I get for posting from a small screen.....

 

Cam Motion stage 2; 4.8 would be a great little tow stick...no lump though

 

Ya, I would like a little chop to the idle.

 

well the truth is most cams don't tow well that have a chop to them....
you can somewhat adjust a choppy idle by the lobe separation angle and the tune but only so much.

 

You CAN have a little lope at idle and still have it smooth out you might need to give it a little more stall though.
Keep the idle low, duration reasonable and some stall would help avoid loading the engine much at low rpm.

For something like this I would consider an aftermarket 12", normally I would say 9.5" only and some guys do tow with those, but if daily and towing is strictly your thing I think the larger clutch a good thing..
I know Edge has 12" units and I think either Yank or Vigilante does, just go with something good, not B&M level.

 

I mean I don't tow often. I plan on getting a boat eventually so I would do that often but I'm talking a maybe 18' bass boat at the largest. I tow a car here and there but that's maybe two to three times a year. I'm sure just about anything would be better than what I have now as far as towing power. My truck currently has a 4.8 so the stall is slightly higher than what a 5.3 would have in this truck from the factory I assume?

 

I drove a 15' box van from FL to WI with a 4.8l and the Allison tranny, man was that bad in TN and KY in the hills.
If you were ok with how it towed sofar I am sure this will all be an upgrade even without additional stall.
3.73 was a good upgrade, I have a crew cab Z71 5.3l with 3.42s it is ok but nothing more than that. I bet your slightly lighter 2wd with the 3.73s and smaller tires??? feels better even before this round of mods.
How something performs is largely perception, and perspective, I think you are going to love the outcome, someone accustomed to a larger engine with 4.10s would be disappointed.

 

Towing and high torque is correlates with high vacuum. A choppy cam will have lower vacuum. If you want a choppy idle, retard your idle timing and slightly reduce your idle speed. Don't compromise an optimal engine set up just to make it sound cool at idle

 

I originally bought this truck to tow my old 18' bass boat because my previous truck (1994 GMC Sonoma with a 4cyl) wasn't doing so good. This truck towed that boat OK (sold the boat years ago when I started my business) but when towing a car it's like the 4cyl was towing the boat. I guess in the end I just want more power with a nice sound. I think 300rwhp would be great.

 

When towing something it's not rear wheel horsepower want it's rear wheel torque.

Take diesels for a example. They always seem to have twice the torque over the horsepower number.

 

Diesels have very low rev limits, a quick googling says the 2001-2004 duramax redlines at 3250. An engine can't make a big HP number without turning rpm, simple math, HP is torque x rpm/5250. a given torque number is more hp the higher the rpm it occurs at.

 

True but with an increase in one you generally gain the other. I want plenty of passing power too which is where the HP comes in.

 

^^ BOTH TRUE POSTS!! It's HARD for a gas motor to make that low end grunt which is needed for towing that's why most guys that tow with gas motors go with a steeper gear to put the motor in the "sweet spot" faster.

Only way to really add that Grunt down low like that is a blower or add cubes!!
A good base line motor to compare to will be the 383 HT from Chevrolet performance. At 2500 rpm the small block Chevy all ready is making 400 ft lbs.

 

Anybody ever messed with swapping in a late model 6 speed to one of these older trucks or is it even possible?

 

As I was driving it today I realized I'm not as concerned with idle lope as much as having killer power so whatever cam gives me the most low end power is really what I'd like out of this 5.3 build. Sure a little idle lope sounds cool but I want grunt. Lol