4.3 V6 too small for good mpg?

[Firebirdjones]

Originally Posted by slotard

, never would've expected a TH400 in a 1/2 ton,

My 77 long bed was a 1/2 ton with a 400 turbo, and a factory 454 in front of it. In those years you could order the big blocks in the half tons, and that triggered a 400 turbo if you wanted an automatic.

[slotard]

I guess that makes some sense. My C20 Camper Special is 350/350 and while they aren't the factory items I believe that's what it had factory, so I would've expected the 1/2 tons to be TH350.

[Firebirdjones]

Originally Posted by slotard

I guess that makes some sense. My C20 Camper Special is 350/350 and while they aren't the factory items I believe that's what it had factory, so I would've expected the 1/2 tons to be TH350.

Yup, with a 350 up front I would expect the 350 turbo behind it. If the 350 turbo trans is original you can bet it was a factory small block truck.

[slotard]

I'd kinda been expecting TH400 because it's a 3/4, if it was a 1/2 ton TH350 would make more sense to me.

[barry1982]

Yes, it is an odd combo. I guess in the late eighties... early nineties if you selected the three speed auto rather than the overdrive, you automatically got the TH400. We got lucky with this truck, I worked for Shell at the time and it was a "surplus" company vehicle. It lost reverse, and the company sold it rather than repair. I picked up the truck for $350 and it only had 40000 miles!
My son and I rebuilt the trans over a weekend, gave it a quick paint job in my shop and he's been driving it for four years now. Was a "plain jane". We threw on a cowl hood, some euro tail lights and installed an after market cruise control.

[Firebirdjones]

Transmission was related more to engine selection that it was to truck ratings.
If you ordered a small block chevy with an automatic, you got a 350 turbo whether the truck was a 1/2 ton or 3/4 ton.

If you ordered a 454 with an automatic you got the 400 turbo, and that could be done in the 1/2 ton trucks as well, I had a 77 1/2 ton ordered like that.

However with that said, most of the small block 3/4 ton and even 1 ton trucks I see most of the time are manual transmission with a very low 1st gear to help get the torque suffering 350 moving when towing something. A friend of mine had a 1 ton, factory 350, with manual trans and granny gear. I couldn't imagine that setup with an automatic, any 3 speed automatic really, if you planned to tow anything, because that 350 needs a little help if you know what I mean.

[slotard]

Mine makes plenty down low for a truck, but the 4.10s help with that.

[Firebirdjones]

When I say down low power and towing, I'm talking about pulling a 10,000 lbs. enclosed trailer or something similar I didn't buy a 1 ton to pull a ski doo, lol.

Yeah you can tow with the 350, I've done it, but when you put much more than 4-5,000 lbs. behind it, it's not much fun, especially on the hills

[barry1982]

I agree about the 454 TH400 statement..... never saw a 454 come with a TH350. However, for some reason I have come across quite a few 2 wheel drive 350 equipped 1/2 ton pickups with Turbo 400's. I'm not positive, but maybe if you ordered the the heavier GVW.... it came with the 400.?? My uncle had a 76 3/4 ton 350 engine 400 trans. ( I had to change it for him once)
Also did a camshaft for a buddy in a 1980 1/2 ton Silverado. It had a 350 /TH400

[barry1982]

I'm not sure if it's true.... but heard GM had a "surplus" of TH400's in the late 80's. With the 700R4 taking over for the TH350's at the time, you got a 400 when you ordered the 3 speed in everything. Makes sense in my Son's truck case. Why would a little 4.3 have a 400 auto?? Does anyone else out there have one of these?

[Firebirdjones]

Always exceptions I'm sure, I never say never. Just stating the norm.

[barry1982]

I bought a brand new 1987 Silverado 1/2 ton short box/fleet side. Was the first year for fuel injection. I had the 305 / 700R4 . Was a great little truck. I wanted the 350, but the dealer told me in 87,you couldn't get the overdrive with the 350, only the 305. If I ordered the 350 , it came with a TH400 or a standard. My buddy bought a used 86 a few months later. His had the 350/ TH400. I recall my truck was much better on gas.

[slotard]

Originally Posted by barry1982

I agree about the 454 TH400 statement..... never saw a 454 come with a TH350. However, for some reason I have come across quite a few 2 wheel drive 350 equipped 1/2 ton pickups with Turbo 400's. I'm not positive, but maybe if you ordered the the heavier GVW.... it came with the 400.?? My uncle had a 76 3/4 ton 350 engine 400 trans. ( I had to change it for him once)
Also did a camshaft for a buddy in a 1980 1/2 ton Silverado. It had a 350 /TH400

Mine's the heaviest 3/4 ton single cab you could buy in '73, 8200 GVWR.

And correct, it doesn't pull like a similarly built bigblock, but a decent 350 with 4.10s will do better than a smog dog 454 (not that they were yet in '73), especially if the 454 is geared tall.

[NONHOG]

I very rarely got above 20MPG in my 08 Silverado 4.3. Heck I think I hit 20 maybe twice?, had nothing against the 4.3. Plenty of power for a half ton trucks needs. 17 around town, 19 freeway.
Only reason I went V6 was the low price tag.

[Firebirdjones]

Originally Posted by slotard

Mine's the heaviest 3/4 ton single cab you could buy in '73, 8200 GVWR.

And correct, it doesn't pull like a similarly built bigblock, but a decent 350 with 4.10s will do better than a smog dog 454 (not that they were yet in '73), especially if the 454 is geared tall.

Ooo, I wouldn't bank on that. I've had both and still have the smog dog 454 (for a reason) It's the torque curve that's important and the 350 doesn't make near what the 454 makes. They still under rated these engines a bit, both 350's and 454's, and even though the 454's in the mid to late 70's were only rated around 230-ish HP the torque rating was closer to 400, and a very flat curve to boot, You can bank they were actually quite a bit better than that, especially in the torque department. A 350 won't pull like it, especially off idle and up through 3,000 rpm where the engine spends most of it's time. You can put 4.88's in that 350 if you want, a big block with a flat torque curve doesn't need gears.
I'll give you a perfect example. Back when I first bought the 79 454 it was still a bone stocker 20 years ago with 70k miles on it. Smog pump and all. It would yank my enclosed trailer around easily. I still had my 350 pickup and at that point I could tell right away I wasn't towing with that anymore.
In 2001 my father bought a brand new 6.0 LQ4 3/4 ton pickup with 4.10's and the 4L80E trans. We both pulled 18' open trailers with our 3800 lbs A-bodies on them, and my old smog 454 would literally just run away from him on the hills. He had to mash the pedal and force the trans to downshift to keep up, otherwise once on the flats I had to slow down and wait for him.
Around here in Arizona with mountain grades, it's no contest. If you want pulling power in a gas engine, these old big block trucks from the 70's-80's and early 90's are as good as it gets. If you want better you have to look at diesels (did that too) Bought a duramax and now don't tow with the big block much.
Anyway, later on several years back I decided to do headers on this old truck, performer intake, tweak on the carb and distributor, bigger dual exhaust, removed the smog pump, and the truck ran 14.70's in the low 90's Not bad for a smog motor that at this point had 95,000 miles on it, didn't even crack a valve cover.
Now today it's recently rebuilt, still stock compression, still stock peanut port heads but with bowl work, 218 @ .050 cam, back to the stock intake with mods under the carb and a modified spacer, same Q-jet, same headers and exhaust, and it actually feels pretty good for an old truck, more off idle grunt than before. Now with about 5,000 miles on the new engine it's starting to really come around. It makes nice flat power to 5,500 and is a ball to drive.

[tucsonjwt]

I got 20-21 mpg city and 26 highway on my 2002 Silverado 4.3 V6 with a 3.73 rear gear but I drive like grandma on her way to church on Sunday. If driven normally, I am sure the mpg would not be much better than a 4.8 or 5.3 - I have had several pickups with those engines also. Rear axle ratio does make a huge mpg difference on any vehicle. I had a 2004 Sierra extended cab with 4.8 and 3.23 rear axle and it was close in mpg to my 4.3 2002 Silverado.

[Flying Hamster]

I've got a 4.3, 5 speed with 3.23 axle in my '06 RCSB. Around town, 15-16 mpg, highway about 21-23 depending on speed. This is with a Leer cap and a bed full of junk. As far as power goes... it goes. It won't win at Daytona, but 110k trouble-free miles and counting.

[Blessed66]

I never really paid much mind to the mileage I was getting (ex-04 ECSB Silverado 1500), but I will say this - the transmission went out on it at about 94k, my wife was driving, pregnant at the time. I noticed a really bad trend uphill for it to really downshift - I mean like, second gear screaming downshift - because it didn't have the guts to maintain speed at cruising RPMs. And ti would do this regularly.

Maybe it was the ECSB, maybe the 4L60E, maybe it was the only time I towed something behind it (from Alabama to Texas, my '66). I don't know. It just always left a bad taste in my mouth (nothing to do with the wife being hormonal at the time, I'm sure ) anytime the 4.3 engine came into a conversation.

That being said, as far as guts - there's a company making V6s with turbos in their vehicles with good results, maybe a 4.3L Turbo would have some guts and still be decent on mileage. I'd love to see real world figures on a 4.3 Turbo. Expected horsepower, torque, fuel mileage, etc.

If I were to guess off of Typhoon power ratings (280hp, 360 lb.ft & 13city/17 hwy), what you would lose in fuel economy, you'd gain in power. But that's also a flawed assumption - engineering has come a long way since the Typhoons and Syclones.

[rayfinseats]

Well, my 383 gets WAY better milage than my 327 did. 30-50% increase.

[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.

[slotard]

Originally Posted by rayfinseats

Well, my 383 gets WAY better milage than my 327 did. 30-50% increase.

Interesting. Is the 383 a lot milder or something? Given similar engine setup and driving style I'd expect the short stroke to get better mileage, and that's even more true if your gearing is the same (as the 327 is happier at higher rpm than the 383).