Guys with 5.3 or 6.0 swaps, I have a question

[85 Jimmy]

What kind of mileage are y'all getting out of these swaps? I know everything will be different depending on trans, gears, and tire size, I'm just trying to get a ballpark number.

I have a 5.3 in my 2005 crewcab Z71 and I average about 16 mpg. When I worked at a hummer dealership I'd look at the average mileage on the H2's with 6.0's and they'd show 12 mpg. But these are completely different vehicles.

I'm getting fed up with my TPI 350 always needing something if I let it sit for longer then a month, so I'm looking into swapping in a 5.3 or 6.0. I'd really like a 6.0, but people think they're made of gold around here, if you can find one.

My plan is 5.3 or 6.0 with a 4l80e (already have one, just needs a rebuild), and a 205 (already have with a fresh rebuild). I'd like to go doubler, but at this point I don't think I'll ever use it. Plus, with the 4l80 and doubler, I don't know what my rear driveshaft angle will look like with the short wheelbase of a blazer with 6" of lift.

 

[blazinzuk]

No clue on milage as I have heard as high as 20 and as low as 12. I think mid teens seems reasonable.


Why the 4l80, 4l60 with a 241 gives you very nearly as good a crawl ratio as three 4l80 with a doubler. I know they are stronger but the 4l60 is a pretty reliable trans especially in later forms

 

[85 Jimmy]

The only reason I'd go with the 4l80 is because I already have one. If I buy an engine/trans combo I'll just put in whatever trans is attached to the engine, as long as it's not a 2wd trans. Also if I can find a 6.0, the 4l80 is what comes behind them stock.

I'd probably be happy with a 5.3, but for some reason I want a 6.0

 

[ashman]

I can't give you concrete numbers because I haven't bothered to check but I can say the mileage is better enough to notice. I went from a crappy running carb'd 383 to a 6.0 (nothing else changed) so it should be expected that my mileage change would be dramatic. I don't know how much worse my 383 was than your TPI engine though.

 

[fubar_k5]

Im getting 15mpg with my mildly built 6.0 in a 94 k1500 on 265-75-16. This is just the base tune I logged a run with efi live this last weekend and sent it to the tuner hopefully receive a new tune by this weekend to try it out. As it is right now if i kept my foot out of it could probably get over 16 easily but its just to much fun.

 

[K30Blazer]

If you are considering mileage (which I was) look for a 4L65e. I know the 80's rob power more. And the 4L60 did come stock behind the 6.0

I personally would be pretty stoked to see 15 MPG That is my hope...

 

[85 Jimmy]

I'm just curious on mileage, I'm sure either engine will get better mileage then I get now. The big factor on which engine I go with will probably be price and availability.

I could use my current 700r4, it has fairly low miles on it. I'd just have to figure out the TV cable. If I happened to get an engine that was drive by wire I guess I could figure out how to tie the TV cable into the pedal it's self.

 

[bigblock72]

I have gotten as high as 16 mpg with mine, I usually get around 12 when 70-75.

I don't recommend running a 4l80 with a 6.0l as it will be a bit of a dog, between the highish first gear ratio and the amount of power they soak up you'll be less than impressed. The 4l60/65/70 is a much better fit unless you plan on making big power.

I've looked at doing a 700r4 with a DBW system and after looking at the throttle control maps I decided it was more work than it's worth. The throttle opening is not a 1:1 with the pedal, it's more of a progressive curve. Making the shift points work with such a screwy setup will be problematic at best. Yes you can adjust the throttle opening map in the PCM but you can ruin the PCM if you go farther than the TAC module likes.

 

[NorCalKid]

I get about 15 with mixed driving and having fun. 71 c20 with utility bed 5.3/nv4500 and 3.73's

 

[sreidmx]

FYI stock 6.0 4l80s come with a 2600-2800 stall to make that gearing difference up.. Crazy..