4.3 V6 too small for good mpg?

[cochino12]

Just picked up a really clean '86 c10 w/4.3 for super cheap. Any idea what kind of mpg to expect? Seems like a pretty small motor with really poor HP/Torque numbers for a truck that heavy.

Thanks

Adam

[manimal]

Not sure about the '86, but my 92 TBI 4.3/5spd gets 25mpg.

[old Rusty C10]

I had one years back.. truck has no real guts and mileage wasn't any better than an 8 they used to say the power of a 6 with the mileage of an 8 I much prefer my 350

[cochino12]

Originally Posted by manimal

Not sure about the '86, but my 92 TBI 4.3/5spd gets 25mpg.

Damn that would be great!

Originally Posted by old Rusty C10

I had one years back.. truck has no real guts and mileage wasn't any better than an 8 they used to say the power of a 6 with the mileage of an 8 I much prefer my 350

That doesnt inspire much confidence

[Matt Man]

I had one in my 06 single cab, got about 17mpg. Wasn't much better than the 8 cylinder really.

[rich weyand]

I had a 4.3 with overdrive and AWD and about 3.95:1 (3.73:1 on short tires) in a '95 Safari, and got 17-18 mpg. It was also really quick with that axle ratio and short tires. It was also about 800 pounds lighter than a K10. Anyway, got 160,000 miles on it and gave it away to a friend who was still running it last I knew.

[Keith Seymore]

My '87 TBI got about 20mpg - 22mpg with an overdrive manual trans and 3.73 gears.

I always thought it was plenty peppy for general use; I drove it yesterday after I hadn't been in it for a while and was still impressed.

I'd be willing to take on any generic untuned 305/350 V8's in a little drag race...

K

[KrazyRay]

Tbi 4.3 good, carb 4.3 bad IMO.

[71swb4x4]

I like my 4.3's. Today I have 2 4.3's, a 4.8 and a 6.0 in 2005-2006 work vehicles. The 4.3's have been MUCH more reliable than the 4.8 and the 6.0. Granted I am just one experience, but it's the only experience I have to go on. Gas mileage is decent, reliability is phenomenal.

[Burbnasty]

The 4.3 mid 90s work truck, was always the same mileage as the 350. Probably cuz it has to work harder to get up to speed i guess.

[Matt Man]

On a positive note, these engines are very reliable.

[Tom]

A correctly running 350 usually gets the same mileage as a 4.3. My 98 5.7 gets 22mpg freeway. They are so reliable because they are a genI 350 minus a couple cylinders. Good motors as far as v6's go and the new all aluminum 290ish HP version is what everyone always wanted the 4.3 to be power wise, really impressive.

[slotard]

Originally Posted by Tom

A correctly running 350 usually gets the same mileage as a 4.3. My 98 5.7 gets 22mpg freeway. They are so reliable because they are a genI 350 minus a couple cylinders. Good motors as far as v6's go and the new all aluminum 290ish HP version is what everyone always wanted the 4.3 to be power wise, really impressive.

I sure wish I got 22mpg freeway in my 350/350 C20... then again, 4.10 rear end makes that far more difficult.

[tucsonjwt]

1/2 ton weighs a lot less than a 3/4 ton truck, so gas mileage will never be very good with a heavier truck. Add a 4:10 rear axle and you can forget good mpg, regardless of the engine. On the other hand, a 3/4 ton truck will haul/tow a lot more. As a daily driver a 3/4 ton is usually a bad choice.

[slotard]

Originally Posted by tucsonjwt

1/2 ton weighs a lot less than a 3/4 ton truck, so gas mileage will never be very good with a heavier truck. Add a 4:10 rear axle and you can forget good mpg, regardless of the engine. On the other hand, a 3/4 ton truck will haul/tow a lot more. As a daily driver a 3/4 ton is usually a bad choice.

I don't think there's as big of a weight difference as you're suggesting. I'd be surprised if it was 10% (for the same cab/bed/engine/tranny, and my single cab long bed 350/350 matches most 1/2 tons, other than the utility bed). The bed and the gearing are what kill mileage on mine.

[cochino12]

I think I've decided to yank this 4.3 in favor of a 350. The quadrajet on this 4.3 is a 4 bbl ? does anyone know what cfm it should be?

[MikeB]

I had a neighbor back in the 80s whose company changed from 5.0 engines to 4.3 in their company Impalas. I still remember him saying the 4.3 had a lot less power and got no better gas mileage.

But if you have a very nice truck with a 4.3, and you find yourself wanting more power, there are aftermarket performance parts available for it (from Edelbrock, for example). Many times an engine with mild aftermarket cam, intake manifold and carb, and more aggressive ignition timing will actually get better mileage than a stock engine. Of course that's assuming your truck doesn't have to pass a state emissions test.

And don't forget to go with dual exhaust, or at least a less restrictive single exhaust system (larger pipes).

[joedoh]

Originally Posted by MikeB

I had a neighbor back in the 80s whose company changed from 5.0 engines to 4.3 in their company Impalas. I still remember him saying the 4.3 had a lot less power and got no better gas mileage.

the 4.3 impala was a V8 engine, a "baby LT1".

My vortec 4.3 v6 trucks get 20-23mpg combined. I had a 5.7 vortec suburban that got 19 highway and I loved that truck, but not for the power.

[csdineley]

cochino12: yes a "Quadrajet" is a 4bbl. And Quadrajet's only came in two sizes 750 and 800 cfm.

I don't know how much a half ton squarebody weighs. But my '87 3/4 ton reg cab long bed 350/sm465 weighs 4900-5000 lbs depending on how much gas I have.

[tucsonjwt]

My 83 C20 regular cab long bed weighs 5600 lbs. empty. What does a similar 1/2 ton weigh? Looks like about at least 1000 lbs. less for a 1/2 ton:

http://67-72chevytrucks.com/vboard/s...d.php?t=430180

[Firebirdjones]

My 79 1 ton SRW single cab long bed 2 wheel drive with a 454/400 turbo scales exactly 5300 lbs. with one 20 gallon tank full. It's loaded with options as well.
With 3.73's I get just a shade over 14 mpg highway cruising, and a steady 12 mpg in town. It's actually very respectable for what it is, my wife drives it daily.

[slotard]

Originally Posted by tucsonjwt

My 83 C20 regular cab long bed weighs 5600 lbs. empty. What does a similar 1/2 ton weigh? Looks like about at least 1000 lbs. less for a 1/2 ton:

http://67-72chevytrucks.com/vboard/s...d.php?t=430180

Odd, mine was around 5200 with a utility bed with a bunch of tools in it. Also a C20 regular cab long bed.

[cochino12]

Originally Posted by csdineley

cochino12: yes a "Quadrajet" is a 4bbl. And Quadrajet's only came in two sizes 750 and 800 cfm.

I don't know how much a half ton squarebody weighs. But my '87 3/4 ton reg cab long bed 350/sm465 weighs 4900-5000 lbs depending on how much gas I have.

I thought it was something like that but 750 sounds huge for that little motor. Thanks

Adam

[83 Silverado]

Its not running a Rochester Dualjet, it the two barrel built in the Quadrajet body with only the primary's and no holes for the secondary's?

[barry1982]

My Son has a 90 1/2 ton with a 4.3 , TH400 auto and a 308 Diff. Fantastic combo.... peppy around town, and still makes great mileage on the highway.
Of coarse the young fella wanted to swap in a 350.... But for a young guy with a limited budget, you just can't beat this thing. Reliable as the day is long