The Stovebolt Site Forums The Shop Area The HiPo Shop 4.3 V6 vs. 350

I'm looking at possible engines for a daily driver project (is that an oxymoron or what?) The truck in question will be a late '30s chevy 1/2 ton. Upgrades will be IFS with disc brakes, maybe IRS, high gear ratio rear end (3.23s or ?) and an overdrive trans for gas mileage. I already have everything except the late '30s Chevy, motor and trans. Driving conditions will be mostly highway with some mountain driving and carrying a moderate load infrequently. My main goal here is fuel efficiency (25 to 30+ mpg if possible) and being able to keep up with modern freeway traffic safely. I've looked at the Chevy crate motors and am considering a 4.3L L35 Vortec or the 350 Vortec. I know either one of these would provide plenty of power for this truck. But they both cost around $1800 so I'm wondering if the 4.3 will really get better mileage than the 350 or if I should just get the 350. I plan to run TBI on it either way. Also, does anyone know of a overdrive manual transmission for a decent deal, new or remanufactured? The Richmond's in the Summit catalog look really nice but at $3k are a little pricey. Does GM have a crate OD trans?

More questions to come. Thanks!

Dave

As you know, they're the same engine, but GM took a hacksaw to one. If you're hauling loads in the mountains, you'll want the 350. for economy you'll want the 6. This six will do the job, but it will slow you down in the mountains. Have you considered the 307? Good torque and better economy than the 350. Of course, I'd vote for a 292, they are available as a crate for about the same price. But I love the six.

Thanks for the suggestion, Fred. Actually, a 292 would be my first choice if I had my preferences. I ruled it out as I didn't know it was still available as a crate motor and I was concerned it wouldn't get good gas mileage. Can I get comparable gas mileage to a v6 with a 292? I would LOVE to run a 292 if it's economical. I love the inline 6 motors and that 292 has some really impressive torque.

Dave

DaveR-good, thought-provoking question there. Certainly an issue which will require careful planning and consideration on your part. I'll add my $.02, just for some more thought.

Several engine choices have been suggested here, I've personally owned two of 'em-my 1972 Malibu ragtop had a 307 V-8 (175,000 mile original, never rebuilt)-that car puffed oilsmoke all day long, but the 40 ft. of rubber it would lay from a standstill is testament to the available torque. Good engine, reasonable gas mileage for a V-8. 4.3 V-6, I've had two, first in my 1991 S-10, second in my 1989 Astro van (Dad's hand-me-down). Both were TBI engines, totally stock, both had high mileage and both were more than up to the task of moving the vehicles they were designed for. About 190 ft-lb torque in stock tune, more if you want to modify a bit. I've yet to own a 350, but in the realm of "stock configuration" small-blocks, they ARE the king of the hill. Unfortunately the mileage won't be as good as the other suggestions offered. I don't have any experience with the big inliner, but this IS the place to get advice on 'em. I think in a tiny truck like yours, I'd give the 4.3 a try, but that might just be me...Best of luck whatever your choice.

Regards,
Wannabe

Dave, the 4.3 would be fine for your application, but I don't think 25+ mpg is a realistic expectation, overdrive and efi notwithstanding. My '97 GMC Sonoma has the OD automatic and sequential fuel injection with a 2.2 four (Cavalier base engine), and the best I've ever seen is 27 mpg. You are talking about a heavier truck with poorer aerodynamics. Twenty might be achievable, though.

Another choice that might be a bit easier in a narrow engine compartment is the 3.4 60-degree V-6 from a Camaro. These are smooth and have great torque for their size and excellent fuel economy. You have to use the matching transmission, though as the fours and 2.8/3.1/3.4 V-6 family use a different bolt pattern than the 4.3, which uses the standard chevy V-8 pattern.

Good luck!

I'm confident that I can get at least 20 mpg with either the v6 or the 350. My 3.4 L Tacoma 4x4 gets 20. My buddies '01 4x4 Chevy v8 gets around 20. Heck, my '50 gets 17 highway with a worn out 350 with a RV cam and worn 4 bbl. But if all I can expect out of a v6 is 20, or maybe 1 or 2 mpg better than a 350, then I'll have to rule that out as an option as v6 motors are just not interesting to me. I thought I might be able to achieve some good mileage with one is all.

So what I'm really considering now is the 292. What kind of mileage do you guys think a relatively stock, TBI 292 can manage with highway gearing and an OD transmission? I'm only interested in highway mileage here, as nothing will get very good around town.

As a side note, I had considered a 4 for this project, either a toyota 22r or an Olds because it can be dressed up to look like an old Offy 4. Is either of these a good option? I know the 22R trucks with fuel injection can do 27 mpg highway.

Dave
'50 1/2 ton, heavily modded, languishing.
'39 1/2 ton wannabe

Agree that 20 mpg is a realistic goal, I just don't think 25-30 is achievable.

292 would be great choice, or even a garden-variety 250. Not sure about fuel injection. Seems to me G.L. mentioned recently that GM trucks for export to Mexico (until recently) had 292s with throttle body injection. Aftermarket EFI is available, but not cheap at all.

Of course, with TBI you have the same problem that plagues carburetors on inline sixes - you can't get the fuel mixture exactly matched between the middle and end cylinders.

Another interesting possibility, if you can find one, would be the 3.0 L GM industrial/marine four. I'd say these would not be performance engines, but should pull well and get good fuel economy.

I have been (slowly) working on a TBI system for my 250. There has been quite a bit of discussion over at Inliners.org on this topic, several people there are doing it. DIY-EFI web page has a lot of info on customizing GM fuel injection systems. Once I have my TBI setup done (hopefully this summer), I plan to put together a tech page.

The TBI will still have the carburetor fuel mix quirks, but it should be far more efficent, and at least a bit more powerful than a carb. The most difficult part is going to be tinkering with the engine computer programming. The injectors for a 4.3L V6 should be just about right for a 250 (4.1L) and 305 injectors should be good for a 292.

Port injection should also be possible, but I couldn't think of a way to work with the siamesed intake ports.

GMCpanel, thanks for the links. I've perused Inliners before, but later, when I get a little time, I'm going to search the site (and this one) on fuel injection. I need to do my homework and I think that DIY efi page is going to come in really handy. You're doing a TBI on your 250? I like the idea of multi-port but I think the machining costs could be prohibitive. Plus the siamesed ports issues. I like the idea of hiding some injectors in a 3 1-bbl manifold for that classic look. I think that might be pricey too, but if I build my own it might be possible. Thanks again!

Dave

What about the smaller TBI injectors for the little GM 4 bangers? Would a couple of those on a multi-carb manifold work? Of course, you'd have to have some special computer hacking done to make everything work smoothly together...

Just a thought.

Regards,
Wannabe

What I've been dreaming about since the Grand Nat's came out is swapping in a 3.8l intercooled turbo. I wonder if anyone has done a swap like this? If anyone would, I throw my vote to the resto-rod'er wannabe Wannabe (no I didn't stutter). And if anyone has any info on a swap like this, please post it, 'cause like I said I've been dreaming about a swap like this for a long time and that '53 is just sitting there in the field waiting for a plan.

Lorne

My original plan was a pair of single-barrel injector pods on a 2 carb manifold. After a lot of thought, I decided that there was going to be a lot more work for a minimal gain with that plan, so I'm just going to be using a 2-barrel TBI on a manifold for a 4-barrel carb. The injectors I am using are for a 4.3L V6 (the 250 is 4.1L), if they prove to be too small I'll go up to the 305 injectors. It will be a while before I have any results, the whole truck is progressing rather slowly. I'm also converting my HEI distributor to computer control to complete the system, but that is another story entirely.