5.3 engine Swap???
Thread Starter
Teching In
Joined: Sep 2006
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From: Dallas Texas
5.3 engine Swap??? So I was pulling my toys on a trailer with my 2002 Z71 Avalanche in some hilly HWY areas and was so frustrated with the down shifting and lack of power, I have decided its time for the 5.3 to go!!! question is which engine should I replace it with 6.0? 6.2? or what? I think I will be happy around 400 HP maybe 425, so maybe a cam and a tune on a LQ4? your thoughts?
A positive displacement supercharger(Magnusson or similar?) would give you the enhanced low end torque you need for towing and something you can do in a day or weekend. At least consider it. Engine swap is a way to go but a lot of work!
Also agree with above post; tuning can surprise you. Also gears help a lot.
6.0 LQ9 would be a good candidate and the most direct bolt-in if that is the route you go.
Also agree with above post; tuning can surprise you. Also gears help a lot.
6.0 LQ9 would be a good candidate and the most direct bolt-in if that is the route you go.
Thread Starter
Teching In
Joined: Sep 2006
Posts: 20
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From: Dallas Texas
The 5.3 has become weaker and weaker, I have 37" tires which doesn't help, already did a nelson PCM tune, the engine is just tired, my last 5.3 seemed to be the same way. I always felt like the Avalanche was underpowered, I could probably do the swap over 2 weekends, tranny is brand new so just the motor is what I feel it needs, we have been using the truck for pulling a 16' trailer with my Can Am Maverick on the trailer (not a heavy pull) we are going to the Ozark mountains in November, traveling 75 mph right now bearly going up a incline the truck is dropping into third and staying at 3000 rpm, I think its just weak.
The above suggestions are all good ones...but...it sounds like you are ready for more displacement.
I think the LQ4/LQ9 will be the most bang for your buck "starting point".
There are some killer 6.0 truck builds floating around...you've been here awhile...you've probably read some of them.
I think your "425 HP" is very doable without breaking the bank.
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I think Mercier and 93M6Formula hit the nail on the head. If you still have the stock gear ratio with taller tires you changed your effective gear ratio in the wrong direction for pulling power. Also keep in mind that going from 5.3 to 6.0 is not that much of a displacement increase. I don't know what your budget is but at the very least get a fresh 6.0 and change gear ratio to match the tires. If you have more in the budget then a turbo or blower would certainly make it pull like a freight train even at 8-10lbs of boost.
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Thread Starter
Teching In
Joined: Sep 2006
Posts: 20
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From: Dallas Texas
I know the 37's are a tall tire but I have 4.10 gears in the rear, issue is loss of power in the engine not gearing, I'm leaning towards building a 6.0 with cam kit H/V oil pump LS7 lifters around 450 hp easy, bump the torque up a bit refresh the tune and see how that does.
Thread Starter
Teching In
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From: Dallas Texas
Hold on Fast Brick....the 5.3 is coming out so the thought here is I'm increasing the HP to 450 with a new build since my earlier post, do you think 4.10s are still to high with that in mind?
I think the stock tire size is 31 and you say 4:10 ratio rear. According to the calculator I use going to a 37" tire you need a 4.89 gear to keep the same final drive ratio.
If this is correct your gearing is way off.
If this is correct your gearing is way off.
I look at it like this..you will increase power output by a decent percentage. Let's say liberally 50%. Likely with no power adder most of that power will be in the higher RPM range. At peak power, 300HP*150%=450HP you are shooting for. That's 150 more HP. Awesome if you can get there. At 1800RPM, you might only go from 100HP to 150HP(again being VERY generous with the increase here) and with either of those numbers in a relatively heavy vehicle with 37" tires and 4.1 gears it is probably going to accelerate like a school bus with a potato in the tailpipe. Yeah, torque makes the most difference down low and I used round numbers but just trying to illustrate it for you. Basically in lower RPMs the difference wont be that much IMO and the gears get you into the power band quicker and more often. You will be happy with a fresh-ish 6.0 but the gears are critical I think.
Thread Starter
Teching In
Joined: Sep 2006
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From: Dallas Texas
Ok, going through my old school train of thought (which IS rusty) you guys are right, gears are going to be changed, which is not a problem I want to go through the axle any way, main question now is which block? I have all the Dallas Texas builders coming up with their thoughts on what we should put in the AVY, all the way up to a LS7 which I'm kinda putting the Kabash on because I want to do a build that is reasonable in price for others that may want to do a similar build, doesn't seem like this has been done with many Avalanche trucks, anyway I will continue to update this with a complete play by play of the build just like I wish someone would have done for me.
Despite common belief to lower the RPM for gas milage, These motors don't like to lug In Low RPM.
You want to be around 2200 RPM while towing. At least 2000 RPM to prevent gear drop unless you hit a steep hill.
The 4.10's with a 37 tall tire is similar to 3.42 with a 31 tall tire.
The 3.73 in my 2006 with 32 tall tires are night and day difference between my 2000 with 3.42 and a 31 tall tire.
The 3.42 set up is always dropping gear to maint speed on hills. not so much with the 3.73. And this is unloaded as well...
For down low and towing I would still go with a 4.10 with a 31-32 tall tire.
For 37's I would go with a 4.88 to get the same ratio for towing.
With 37's
At 2000 RPM you would be going just over 65 MPH
At 2500 RPM You would be going around 81 MPH
The Power will help but You're going to kill another motor if its lugging or hunting to maintain speed while towing.
The gears will definitely help and are alot cheaper than the motor.
Then I would at least freshen the motor and slap a mild cam in there. You don't need much else especially for a towing application. If you want to do a motor swap then a 6.0 LQ4 would be a direct drop in.
A 6.2 will require alot of extra money to retrofit since it is a different series of engine's.
Is weight a concern? If you don't mind the extra weight(somewhere right under 100lbs) of an iron block, LQ4/LQ9 is an affordable place to start. LS2 is 6.0L with aluminum block and a few other differences but can be used as LS1 with LS1 harness for about $100 worth of wiring adapters. If you want to go with better internals, boring and stroking your LM7 block is an option to get to about 6.0. Long stroke builds torque.
I'd find a nice low-mile LS2 personally. It's exactly what I am replacing my LM7 with now. 50K miles and came with 243 heads already for $2500. 400HP factory rating so cam and a tune and you are at 450.
I'd find a nice low-mile LS2 personally. It's exactly what I am replacing my LM7 with now. 50K miles and came with 243 heads already for $2500. 400HP factory rating so cam and a tune and you are at 450.
Deals are around if you look and are patient. You could get your 4.88s and then look around for a motor for a while. 
Save by using your LS1 PCM and wiring and such. I got hooked up with a guy in New Orleans that watches for wrecked LS vehicles and makes good deals parting out. If that is driving distance, I can put you in touch. This was a long block and I transferred all of my LS1 stuff over so complete motor is a bit more. I didn't want the car intake and accessories anyway so it worked out OK. I passed up a 70K-mile LS2 from a Trailblazer SS COMPLETE with all truck accessories and intake for $2600 the week before(kicked myself for that). I am adding AC to the CJ7 at the same time and wanted to keep the weight balance roughly what it was before with the LM7 and no A/C. Really not a big deal but that's how I convinced myself.
Good luck with your build.
Save by using your LS1 PCM and wiring and such. I got hooked up with a guy in New Orleans that watches for wrecked LS vehicles and makes good deals parting out. If that is driving distance, I can put you in touch. This was a long block and I transferred all of my LS1 stuff over so complete motor is a bit more. I didn't want the car intake and accessories anyway so it worked out OK. I passed up a 70K-mile LS2 from a Trailblazer SS COMPLETE with all truck accessories and intake for $2600 the week before(kicked myself for that). I am adding AC to the CJ7 at the same time and wanted to keep the weight balance roughly what it was before with the LM7 and no A/C. Really not a big deal but that's how I convinced myself.Good luck with your build.