2004 Silverado 4.3 V6 Vortec

[mechman600]

It would definitely help. I would also find a rear end with a much higher ratio, or change the gearset in your existing diff. If you can make it chug at 1500 rpm @ 60 mph (Lockup T/C, OD and 2.75:1 ratio will nearly equate to this), the mileage will likely surprise you. In a good way. Maybe with some aeromods (especially a box/bed cover), skinny tires pumped up to ridiculous pressures and a very well tuned engine (as well tuned as you can get with an old V8, that is), you might achieve 25 mpg.

My first car in high school was a '79 Volare, 318 2-barrel, 3-spd torqueflite with lockup and 2.76:1 gearing. It was a Chrysler "Lean Burn" system, an epic fail that I swapped out for the distributor from a van. Even with no overdrive (2200 rpm @ 60 mpg) I averaged 21 mpg, about 50% highway, with 200K miles on it. I sold it for a Toyota Tercel 4-speed manual that got about 38 mpg.

[fujioko]

I think 20+ MPG in an El-Camino is possible.

289 V8 with a smallish four barrel and a modern auto or manual transmission.

Tighten up the suspension ...El-Camino has sort of a marshmallow suspension.

I think you would see some decent numbers in the low to mid twenties. Of course you would also need to drive the car efficiently.

….But really…. an El-Camino should have a 396 big block with a Muncie M21 and a 4.11 12 bolt posi.

That 70’s sound of big block Chevy barking that insane V8 roar! ….I wish gas was 25 cents again!

[mja1]

Lethedethius - how goes the 4.3 silverado? Any new things you've tried yet? I'm new here have an '06.

about the ignition system - no one makes any cool aftermarket coils for these year model 4.3's so we're out of luck with the capacitive discharge ignition boxes. But that's okay because we're going for mpg's. The stock inductive system, although it doesn't give multiple spark at lower rpms, does allow for a longer duration. Longer duration means more complete burn +accuracy. The stock coil is more than hot enough, and the GM ECU is more than you'd ever need for tuning to the last drop of fuel esp N/A. GM LS and truck ECU's are some of the best written programs out there IMO. Allowing you to tune for much more precision over any aftermarket MSD or Crane (or even high dollar ignition systems for N/A engines) ever could. The reason you'd want to switch over to an aftermarket ignition on a newer vehicle is if it's not pumping out enough volts to keep up with hp... on our little 4.3's we'll run out of fuel looong before the full spark potential of the stock ignition system is reached.

A lot of people love the rarer metal spark plugs, but our 4.3 ignitions aren't putting out that much voltage to warrant an 8$ plug. ngk, champion, (or stock) in the stock heat range and gap them correctly. I prefer copper because they're cheap and I need to change them about 15,000 miles, so it forces me to read the plugs more often which I see as a good thing. Copper plugs on our 4.3 will not change the performance/mileage vs fancier metals, they will only wear sooner/increase gap sooner over time being a softer metal

No need to upgrade injectors, even if we could. In fact, for gas mileage you'd ideally want to "downgrade" injector size somewhat for greater accuracy. But tuning for new injectors is not at all for the beginner. The other problem is there are only 2 aftermarket options available to change 4.3 injectors.. 'wynjammer' modified spider assembly (only for higher hp applications) - or a mercury marine manifold (a good option, can fit whatever size injectors we want, but the heavy iron will negate the effects strictly for gas mileage).

Best option is buy an aftermarket ECU (ebay 80-100$), put it in the truck and make sure it works. Keep the original around. Then send the ebay ECU in to wait4meperformance for a 'gas mileage' tune. Will net a few more mpgs on high octane fuel, give them a call before you buy an ECU they may have them cheaper. If you want to use 89 octane, may have to tune yourself with EFI live or HP tuners and a wideband. The potential is there IMO to gain around 2-3 mpg with mail order tune, and as much as 5mpg tuning yourself.

[Lethedethius]

Hi guys I had to take a break on both the truck and the el camino to make time for a career move-I am back in Active Army now so I can get back on this stuff. I'm going to focus primarily on the El Camino at this point-it needs the upgrades anyways so I will actually be getting a new Intake manifold with a 4barrel carb probably 500-600cfm, swapping to a single exhaust (already got the y pipe), I may(unsure as of yet) redo the air filtration system and make it more of a modern setup. I will definitely be stiffening the suspension but there is a weight factor to consider, I think I will be able to cover the bottom of the Elky seeminglessly without much effort. I will keep everyone apprised-I have to go pick up my El Camino next week.