Inline 6 Fuel Mileage

[Tom]

Why use a 292 I6 when you can have a 283 v8? The 283 will sound so much better if nothing else. Lots of head choices to tailor your combo too.

[Oregoon]

Originally Posted by Tom

Why use a 292 I6 when you can have a 283 v8? The 283 will sound so much better if nothing else. Lots of head choices to tailor your combo too.

Great question Tom! First off, sound is subjective. Personally, I love inline gear-whine and the sweet smooth exhaust note of a well-tuned 120-degree six. I think a 90-degree V8 sounds like it's fighting itself.

You may have other opinions. Just as valid!

As to why use a 292 vs a 283? Depends on what you want to use your truck for...

283: 275 ft/lbs @ 2400 RPM

292: 275 ft/lbs @ 1600 RPM.

Those are excellent motors to compare. One is known for horsepower, the other for torque, yet they're very similar in displacement and make almost the same peak HP--175 @ 4000 rpm. Of course, a 292 sounds horrific at that rpm, whereas the shorter-stroke 283 sounds a lot happier...

Totally different engines for totally different applications. Different strokes for different folks.

Personally, I like low-end grunt. Torque moves vehicles. The power of an I-6 is down in the bottom end, where I think it it needs to be for a truck. A V8 is reliant on crank-counterweights to overcome it's secondary balance problems, whereas a 6 is in perfect balance by design. An eight will make more torque through the entire powerband, but it fights itself down low, and that's where the bulk of the power is needed in a full-size truck--provided you are hauling things, looking for economy, or wanting to get off the line in a hurry.

Furthermore, a simple rear-end (or OD tranny) swap makes an I-6 more than fast enough on the highway (if that's your bag), and some head and intake/exhaust mods can turn a six into a bracket-monster.

You can do the same things with a small-block... In all honesty, what can't you do with a small block?

Well, you can't make it a stump-pulling low-end brute without spending some money, whereas you can turn the key on a stock 292 and provided you have traction, you can more or less pull a barn down. But good luck getting her over 70!

In other words, simplicity, longetivity, and low-end. And for some reason, some of us just plain love 'em!

Now if we could just get an affordable cross-flow head...

Until then, see you at the gas station. You'll get there first, especially if we're both on the freeway!

[greg64]

I liked your summary, Oregoon. Not only is the 292 vs 283 a valid comparison, but I just happen to have both engines. The 292 is in my 77, and the 283 is in my 64.

The 283 is faster on the highway, and can easily cruise at 70. The 292 is cranky over about 60, but I've had it up to 90, just once.

But when trying to get a load moving, the 292 is the clear winner. I've had both rigs pulling a trailer with a combined weight of nearly 9000# (took both on to a scale). The 283 needs throttle to get moving or it will stall. The 292, you can just let the clutch out, no throttle and off you go.

I can't compare mileage, because the 283 has overdrive and the 292 doesn't.

The 283 likes revving a lot more too, with it's short stroke. 4000 is no problem for it, but it really feels like I'm pushing the 292 too hard at that speed.

[enaberif]

Its so easy to say a 350 has no torque but then you forget how easy it so to change the powerband of a 350 so easily.

Toss a new cam and lifters into a 350 and you'll have more low end grunt than a I6 can provide anyday. For example in my 350 I've put a comp cams 12-300-4 and based off what I have read can make gobs of torque around 2500rpm.

[greg64]

I don't disagree that the 350 can make a lot of torque. But have you got a cam that puts the torque peak at 1500? That's where the 292 peaks, and also why it has limited HP at more revs.

[enaberif]

Originally Posted by greg64

I don't disagree that the 350 can make a lot of torque. But have you got a cam that puts the torque peak at 1500? That's where the 292 peaks, and also why it has limited HP at more revs.

The 12-300-4 powerband lies between 600-4500 rpm.

[greg64]

Impressive. I'm thinking that this might be the comp cam I have in my 283. I'd have to check my notes.

[Oregoon]

You can cam an I-6 to perform in a variety of ways too, if that's what you're into...

For me, aside from the useful stock torque, I like the fact there are seven main bearings, I like the fact it's internally balanced, I like how simplistic it is (not that a small block is much more complicated), and I like how absurdly roomy things are in there. I like how rugged and all-but indestructible they are. Form follows function, and to my eye, they're a very pleasing engine, especially when dressed up a bit. I like that if I maintain my six properly, I can run it to some extremely high miles, and during that time, get to know it like a family member.

Years ago, I hauled engines for a living, and we had a Ford Van with a stock 300-6 with 400K on the clock. It ran pretty good, though fouled plugs from time to time.

We'd regularly pick up Chevy sixes with 300K-plus miles, most running pretty well, just getting tired, and some in industrial applications that really put the abuse on a motor. That sold me on the six, and the machinists I worked with all sang their praises.

Of course, they were quick to say that V8s are excellent too, and great at what they're intended for.

Personally, I see no real reason for comparison when we can take Greg64's approach and have them both! I love my six, but I'd like a second truck with an eight, too. And a third truck with a diesel, and a fourth truck with a two-stroke Jimmy, and a fifth, sixth, etc...

[greg64]

Seeing the longevity of the 6 and looking at the internal construction sold me. Try working on the distributor on the 6 vs the SBC too.

Just need that darn aluminum crossflow head to really wake the engine up. The 4.2L inline 6 (Atlas engine) is a modern version of the I-6. But no parts interchange with the old 196/230/250/292.

I'd love to have seen a BBC derived I-6. The 250 is quite similar, architecturally, to the SBC design. It would have been neat if GMC had built an I-6 with 454 sized pistons and rods for their trucks, but instead, they built the V-6 family (weirdo engines if you're never seen one).

And if could turn down the noise, I'd have a Detroit Diesel too!

[Oregoon]

Those 305/351/478 sixes were neat, as was that 702 V12.

Just weren't that popular, I guess.

Speaking of weird stuff, I got a '70 IH Travelall earlier today, with a 304 V8, Chrysler 727, and a divorced 205 -t-case. Runs great, and it cost me a 12-pack of beer. A buddy gave up on it after having the engine and tranny rebuilt, and wanted to see the truck go to good home.

It surely did! Been messing around with it today. God, it runs perfectly. Haven't owned a V8 in years!

[Oregoon]

Greg, there are the GMC 503 and the 707... Both inliners, and probably use about a gallon a second!

I've seen the 503. Never a 707. Supposed to be torque monsters, go figure.

[greg64]

Hey Oregoon. Ya, I'm aware of those big gmc sixes from early years, but have not seen any in person. Of course, they'd have to be a gas hog, but think of the torque!

That IH 304 is supposed to be a tank internally. And I think there's a 4 banger derivative of it (like the half a Pontiac 389).

My suburban was originally built with a 305E, but that engine was long gone before I ever bought it. If I was building a show truck and not a driver, I would have found a 305 or 351 to use. It's a sure way to confuse guys at a show and shine.

[Oregoon]

Yeah, everything on the IHC trucks is overbuilt! Not the most fuel friendly rigs, but about as tough as they come.

I'm thinking I might try my hand at putting a Chevy TBI on the 304. It's a fairly common swap, and is said to improve economy and power. The current Holley 2BBL is in good shape, but I am not a fan of those carbs.

Of course, I still have a lot to do to my '74 GMC--clutch, and front brakes--so the IHC/TBI shenanigans will have to wait. If it works out, I might consider converting my 250-6 as well.

[greg64]

The Chevy TBI is a great unit. I ran one for a few years on my 6, and it worked great. Until the Holley ECU I was using crapped out. I'm trying to scrounge the parts necessary to do Megasquirt with the TBI, but it's a very low priority, so you know...

One thing I can tell you for sure is the multi-port EFI on the chevy 6 doesn't work because of the siamesed intake ports. I ran this for a while, but it was never right, and I later learned why it would never be right.

[Oregoon]

Those ports are the weak point in a head that already doesn't breathe well.

How does a TBI work with lump-ports? I have an extra head and was thinking of doing a bit to it... Totally bench-building at this point, but if I do convert my 250 to FI, I'd like to get the most out of the head.

I went to the local wrecking-yard today, and while I didn't find a factory white rear-bumper or any decent shoulder-belts, there is no shortage of TBI stuff. I'm thinking the IH 304 experiment may get pushed forward. It's a cool truck, bit not anywhere as nice as my GMC, so I'll use it for the dry run. As you said, the 304 bottom-end is simply massive and near-impossible to kill, so it's about as good a guinea-pig as one could want.

[greg64]

I don't see why the TBI wouldn't work with the lump ports.

As for throttle bodies to grab at the yard; there are three "Model 220s". These are the two barrel jobs, and the most common. The difference between them is throttle bore. The small v6 used 1-3/8" throttle plates (good size for the I6). But the injectors on the small TBI are pretty small. It barely keeps up with a 250. The 4.3L v6 and 305/350 used larger throttle bore and larger injectors. There's a number of different sizes on the injectors. Watch out for the 4.3 specifically, because some (not all) deliberately have different sized injectors. The last model is for the 454 and it had 2" throttle bores. I'd avoid that one too, because it has the most value as an upgrade for guys with a hot 350. It's also too big for the IH or I6.

[Oregoon]

Many thanks! I was wondering which would be the best bet.

[D13]

So, my nickle.
My 250 went 400, 000 miles without removing the head or pan.

Driving my dad's 3/4 ton, 250, 3OTT, 3.42, 8,50-16.5's, he got 15mpg, I got 17 short shifting and keeping it under 50mph.

Aero is poor on these trucks. Speed kills your mileage.

[Oregoon]

Originally Posted by D13

So, my nickle.
My 250 went 400, 000 miles without removing the head or pan.

Driving my dad's 3/4 ton, 250, 3OTT, 3.42, 8,50-16.5's, he got 15mpg, I got 17 short shifting and keeping it under 50mph.

Aero is poor on these trucks. Speed kills your mileage.

I can't tell you how many times I've heard of sixes going way over 300K with no real hassles. And I've seen plenty, too. Such tough and simple motors!

[greg64]

My old 250 must have gone at least 100K before I replaced it with a 292. But the 250 was already old, and of unknown background before I put the 100K on. And the only reason I retired it (still have the motor) was because it was leaking oil everywhere (the usual places).

[Bigstevex4]

I worked with an old mechanic from NY what he said they had Dozens of the 250 sixes in Cecker cabs with over 500,000 mi.

[greg64]

Wow, that's a lot of miles! Pretty much diesel mileage, but it makes sense. The internals are much stronger then the HP levels that these engines crank out. Guys in Brazil are able to run the stock block up to 1000HP using turbos, and the block doesn't give out. Plus those 7 main bearings. Plus a good and simple oiling system.

I'd love to figure out a turbo some day; not for racing, but to overcome the crappy head flow. Bring the engine up to 1HP per CI. A 300 horse 292 would be plenty.

[Oregoon]

Here's a little inspiration for you, Greg!

(I know, I know, it's a Ford, but according to Leo Santucci, our heads breathe better, and with some lump-ports and a turbo, a 292 in a short-wide would be a hot ticket!)

Great read, BTW: http://www.hotrod.com/cars/featured/...ford-maverick/

[greg64]

Thanks Oregoon! My parents had a 70 Maverick, with a six, when I was a kid. I liked that car, but there's no way it would run 10s!

Have you seen the Brazillian turbo exhaust manifold for our engines?

[Oregoon]

This one?

http://www.spaturbousa.com/chevy-ii-...rbo-manifold/p

Oh yes! $673.63 before shipping... Spendy, but man would it be fun!