Difference in gas mileage between BBC and SBC?

[team39763]

I'm in the market for a new tow vehicle.  I was going to build one, but my idea of a tow/travel vehicle isn't up to my wife's standards.  So, we're trying to sell the Ford(4.6L too weak to pull), and looking at a few Blazers, Z71's, and 3/4 ton trucks(some duallies). Here's what I found so far.

1. 1997 Z71 with vortec 350 and 5speed trans.  I figured I could swap in a 400 shortblock  and maybe some headers.  It has about the same amount of cab space as the Ford.  Mileage?

2. 1987 K5 Blazer with a 454 and TH400.  The truck won't be driven a lot, only on trips to the track and to see family across Texas.  With the right gears, could this get decent gas mileage(assuming I drive easy).  What mods would make this get better mileage?

3. 1993 3/4ton Dually with 454 and unknown auto trans.  My wife doesn't really like the looks of these older dually trucks, but we figured we could hold heavier stuff with it.  On the other hand, it's no bigger than the Ford[cab] and I'm sure it's an expensive hassle to replace the dual wheels/tires.

4. 1994 Dually with 350 and unknown auto trans.  Same as above, but maybe better gas mileage?

5. 1995 3/4ton Suburban with 454 and auto trans.  Plenty of seating and doesn't look bad.  I'm sure this is a heavy truck, so I don't know about the gas mileage.

6. 1997 Tahoe with vortec 350 and auto trans.  Plenty of seating.  Would the 350 be enough to get this truck moving and tow my truck and trailer?

I'd really like to have a big block truck, but how bad is the gas mileage really?  The truck's only major job would be to tow.  How will it compare to a 350 trying to pull the same load? Which would ya'll choose?

[joesgarage71]

 I'd go for number 5 the Sub or 3, duallys really pull good, I always like to tow with a heavy truck and theres lots of room for your stuff. The mileage will be better with the BB pulling the same load. Make sure you have a good trany cooler, The lone star is hard on tranys.
 Steve

[dunedigger]

My buddy has a 1999 chevy one ton with a 454.  He gets around 11 on the highway.  We pulled up a really heave trailer once with my truck on it about a 4 hour trip and he got 10 flat there and back.  70 mph the whole way.

[Stewart G Griffin]

i don't have time to get into it real deep right now, but i am actually looking for a 1ton crewcab myself for similar reasons as yourself.


#1) can't comment right now.
#2) Disaster;  If you are going to drive from alaska to texas, you will pay more in fuel than what you paid for the truck.  10-12mpg   15 tops.
the right gears (2.56 or higher if possible)
Lower it as much as possible
get rid of the 4x4 and switch to 4x2
You get the picture---drastic mods.

#3-#6 can't comment on right now,although 4 will get better mpg than 3 but not much--1-3mpg better and 6  is probably the best out of the bunch and the one i would probably pick, although i don't know exactly how much weight you need to tow?

The big-block has never made sense in these trucks unless you have a business(you're using it to transport drugs) or you have some other business, i.e., construction co or delivery co where you're not driving that many miles with it---local, no more than 30 mile radius.

i was contemplating switching to a smaller cubic inch engine---i.e., 283, 262 vortec v-6, or even smaller, but then i realized this would compromise the towing/hauling capacity of the truck which is the reason why i would buy one in the first place.

So, i've decided that i'm only going to look at diesel equipped trucks.  25mpg when empty, yet still has 10,000lb GVWR.  (the one's i'm specifically looking at have the 6.2 engine).

So, i feel that unless you have a special situation, as described above, only diesels make sense in anything at or above 3/4ton truck level.  i think big-blocks only makes sense in corvettes---where you can still get decent mileage.  i don't think gas has ever been cheap;  The cheapest i've seen gas was .86 cents and that was in 1981.

[red4wd]

I would have to say of the options you have laid out #1 or #6 would be my choices.  The 350 five speed would make an excellent towing setup for your truck plus you would have close to the same amount of room you have with your current truck. 

[team39763]

My race truck is a good 3600lbs by itself and the trailer we use is pretty heavy duty compared to other trailers we pulled.  My wife and I are also starting a [mobile] Nitrous business, so we'll be transporting mother-bottles and maybe even a 60gal compressor along with the nitrous pump.  I like the torque of the big block, but on the other hand, I'm pretty familiar with 350's and I can replace it for almost nothing if it goes out.  I just need to be better off than what I have now.  This little 4.6L could barely break past 55mph on the 20mile trip to the local track. 
I forgot to mention, I found a few 80's Blazers with the 6.2 diesel, but I'm not familiar with that engine at all.  I remember hearing about great gas mileage though.

[Captkaos]

I would say 3,4,5 based on the vehicle description.
454's are generally going to get the same mileage pulling or not, generally around 12mpg.

The longer/heavier the vehicle the better it will pull/stop.  You don't want to tow with a Blazer..

[Blazin]

I say stay away from Blazers, short beds. Wheel base is to short. A loaded two place snowmobile trailer will push a short wheel base truck around in a panic stop or less than ideal road conditions. I would also stay away from 1/2 tons. Just don't have the breaking ability, or tow load.
Stick with a 3/4 ton or bigger. I would stay with the 1 ton dual wheels. The extra width is handy when towing at higher speeds. Very stable, not unpredictable. I know small blocks much better than big blocks. But i will tell you once you have towed with a big block you won't ever want a small block for towing a heavy trailer again.

[team39763]

Well can you guys tell me this: Will a similar sized smallblock get the same mileage as a bigblock.  Lets say 400SB against 396BB or 402BB.  Could I get the same pulling power by swapping in a 400smallblock with the vortec setup?

[Blazin]

My opinion here, but a big block is always going to loose in the mileage dept. Might only be by a few MPG or it could be as much as ten or more MPG. Depends on the work load of the truck, driving traits, etc. As

[Stewart G Griffin]

OK; Apparently i have you confused with someone else---you don't live in Alaska, you live in Texas?  This may be significant.

How heavy, to your best guestimate, is the truck, trailer and all equipment?  Is the trailer enclosed or open deck?

As a more logical alternative, you may want to consider the trucks with the diesel 6.5 N/A or turbo.  For instance #3,4,5 with this engine would make excellent haulers.

Another avenue is to look into the trucks with the duramax/allison combo.  I'm not sure when they first started equipping them this way.  i may end up getting one of these trucks.

Also, since you're in Texas, you have a few Carmax'es and they have a pretty good selection which you can check out online.  i may end up going this route myself.  i'm not saying carmax is better than buying from an individual owner.  Actually, if you can find a good truck from an individual it is better.   But i think carmax is ok.

Gasoline in anything above 1/2 tons really makes no sense.  Only diesels make sense.

P.S.  As far as similar sized small blocks vs. big-blocks, i feel that the mpg will be about the same.  But one thing to consider is bearing size;  Smaller bearings=less friction=slightly better mpg.  Also, the small block is lighter than BB.

[zieg85]

 But i will tell you once you have towed with a big block you won't ever want a small block for towing a heavy trailer again.
[/quote]

I agree.  My 85 C20 in my avitar/signature gets me 15 on the open road at 65-70.  It is as close to a 1 ton as a 3/4 ton could be with the 8600GVW rating.  I have towed several heavy loads and mileage goes down to 11-12.  When it was my uncles he used to pull a heavy 5th wheel 35 foot camper and get 13.  I also have friends with the same 454 in a similar truck with a 3.73 or 4.11 and they can't pass a gas station topping out at 6-7.

[Dragon]

From your ballpark description, I would say #3 or #5 would be better suited for your needs(Truck,Trailer, and anything else). Would agree with Blazin, a 1ton 454 with a 4L80E is a better option...

Realistically a Z71 with Vortec'd 400 5spd wouldn't be able to handle the load, dog pretty bad, suck gas like a mugger(Bout the same, if not worse than a BBC), and burn up the trans quickly....

[VileZambonie]

A big block vs small block with the same displacement will not get the same mileage. Think of it like this...it's a baby with it's baba (sbc) or fat slob with a 7-11 big gulp (bbc). The ports on a big block are ginormous compared to small blocks. They breathe better and can be very inefficient as far as fuel economy is concerned, however they are more volumetrically efficient. If mileage is your primary concern though and you are pulling/towing the bbc may be more favorable as it won't have to work as hard. If you have your rig set up correctly and geared properly you can get fairly comparable mileage but better pulling power with the BB. If you've never owned or driven a bb truck you should try driving both and see how you like it. It really is a totally different feeling driving a BB (good feeling)

Gasoline in anything above 1/2 tons really makes no sense.  Only diesels make sense.

[Fordeatinz71]

i'd probably recommend #5...seems like it would work out well for you/your family.  i mean, out of that list that's what i'd pick.  STAY AWAY FROM THE BLAZER!  i love K5s and that would be bad to wheel but HORRIBLE to tow with.  have you ever towed with a short wheelbase vehicle?  there is a reason all your tow rigs are long wheelbase.

if you can afford it, i'd strongly recommend a newer DMax/Allison combo rig...