Considering an engine swap (has to do with towing)

[hblair]

Hi guys, new here.
I have a 1992 c2500 with a 454 and 3.73 gears. I bought this truck with towing my boat to the Gulf and back in mind. About 350 miles each way. I also usually drive it daily. The boats a cabin cruiser. Not sure about the weight, but I'm getting 7.8 mpg towing it. Needless to say it doesn't take long to add up. I spent about 350.00 on the last trip (just gas for truck). I like the power of the 454 but am considering swapping for a 350 throttle body engine. The truck has a 4L80E transmission. I'm wondering what kinda mileage gain I'd be be looking at. Or possibly a vortec engine. I've done a lot of searching here and haven't found the info I'm looking for.

I'm hoping I'm posting in the right forum. Thanks for any info.

[19trax95]

Towing, both motors would get around the same. Just driving the 350 will get a little better MPG. The 454's usually get the same MPG regardless if towing or not. If you do go 350 definitely look for a vortec

[hblair]

Towing, both motors would get around the same. Just driving the 350 will get a little better MPG. The 454's usually get the same MPG regardless if towing or not. If you do go 350 definitely look for a vortec

Really?? My brother had a 93 k1500 and says he got 16-18 mpg on the hwy (without tow). I would have thought a vortec engine would do much better without a load and at least a few mpg better with a load. That doesn't make sense...

[Chriscon7]

By vortec do you mean LS series motors? Cause a 6.0 swap would net some gain I suppose

[hblair]

By vortec do you mean LS series motors? Cause a 6.0 swap would net some gain I suppose

I'd kicked around the idea of a 5.3 actually. Local yard has an 05 for about 750, with about 80,000 miles. My dad has an 07 silverado extended cab with a 5.3 vortec and it pulls the boat fairly well.

[kcb37]

DDing a 454 sucks for gas, towing still sucks gas, but hears a question for you.
You said you got around 7.5 mpg pulling the boat, what do you get unloaded?
That 454 will not have to work as hard as a small block be that a 5.7, 5.3 so your mileage towing will go down less with a 454 then with a small block. Thus your towing mileage would be about the same eitherway.

[hblair]

DDing a 454 sucks for gas, towing still sucks gas, but hears a question for you.
You said you got around 7.5 mpg pulling the boat, what do you get unloaded?
That 454 will not have to work as hard as a small block be that a 5.7, 5.3 so your mileage towing will go down less with a 454 then with a small block. Thus your towing mileage would be about the same eitherway.

I'm not sure on the unloaded mileage. I haven't checked it, but I think around 10 is normal with my setup.

[phoebeisis]

My 1/2 ton 2wd 1998 Suburban-fancier fuel injection system and Vortec motor-5.7 gets 20 mpg at 60 mph-maybe 19mpg at 67mph
The same year 454-figure maybe 13mpg at 60 12 mpg at 67mph.
I rarely tow- but spark ignition motors in 1/2 ton 3/4 ton all seem to get about 7-9 mpg when they tow heavy-6000-7000-8000 lbs.
Bottom line-don't make this engine switch to get better towing mpg.You'll be lucky to get 1mpg better with the 5.7 while towing
Figure -best case 8 mpg 700 miles=87.5 gal x $4/gal =$350
5.7 best case 9mpg 700 miles= 77gal x$4/gal =$311
So you save $39 per trip AT BEST
12 trips per year =$450/yr
Figure all up it will cost you close to $1500 plus LOTS of work
4 years to break even
AND you might not actually get better mpg towing-you probably would if you kept your speed down- but that 1 mpg better-pure guess and nothing I would count on.
The whole time you would have a somewhat "less good" tow motor

I'm a MPG nut-but I think your best bet is to drop 5-7 mph off your tow speed-you'll get the same improvement in mpg-add maybe 50 minutes to trip time on each leg?? But less stressful trip since slower tow is easier tow(unless folks are running up your tailpipe-which maybe they will on interstate??
Luck
Charlie
PS No good way to get good mpg towing a heavy boat with a spark motor-other than slowing down-or a really modern-expensive turbo diesel($50,000) or maybe that Ford 1/2 ton 3.5 twin turbo spark motor($30,000+)
Drop your speed if it is safe on your hy and you have the time.
If you go to a SBC- get the most modern one you figure you can get to work in your truck-the 5.3 of some vintage-might add a bit more mpg towing-geared right-

[hblair]

My 1/2 ton 2wd 1998 Suburban-fancier fuel injection system and Vortec motor-5.7 gets 20 mpg at 60 mph-maybe 19mpg at 67mph
The same year 454-figure maybe 13mpg at 60 12 mpg at 67mph.
I rarely tow- but spark ignition motors in 1/2 ton 3/4 ton all seem to get about 7-9 mpg when they tow heavy-6000-7000-8000 lbs.
Bottom line-don't make this engine switch to get better towing mpg.You'll be lucky to get 1mpg better with the 5.7 while towing
Figure -best case 8 mpg 700 miles=87.5 gal x $4/gal =$350
5.7 best case 9mpg 700 miles= 77gal x$4/gal =$311
So you save $39 per trip AT BEST
12 trips per year =$450/yr
Figure all up it will cost you close to $1500 plus LOTS of work
4 years to break even
AND you might not actually get better mpg towing-you probably would if you kept your speed down- but that 1 mpg better-pure guess and nothing I would count on.
The whole time you would have a somewhat "less good" tow motor

I'm a MPG nut-but I think your best bet is to drop 5-7 mph off your tow speed-you'll get the same improvement in mpg-add maybe 50 minutes to trip time on each leg?? But less stressful trip since slower tow is easier tow(unless folks are running up your tailpipe-which maybe they will on interstate??
Luck
Charlie
PS No good way to get good mpg towing a heavy boat with a spark motor-other than slowing down-or a really modern-expensive turbo diesel($50,000) or maybe that Ford 1/2 ton 3.5 twin turbo spark motor($30,000+)
Drop your speed if it is safe on your hy and you have the time.
If you go to a SBC- get the most modern one you figure you can get to work in your truck-the 5.3 of some vintage-might add a bit more mpg towing-geared right-

Thanks for the information. I've milked all the mpg out of the 454 I could. I maxed the air pressure on the trailer and truck tires and do run pretty slow on the interstate, 58 to 65 mph unless going down a hill. I'm thinking I could save a lot of money when not towing, and like you said, prolly save a fair amount towing with a 5.3 vortec. I love the 454 power but it sure is expensive...

[phoebeisis]

I'm a mpg nut-I mildly hypermile(Pulse and glide in city-max sidewall tire pressure-and shut it off at redlights and stopping at bank lines- if I think the light is over 40 seconds-that is since I replaced my older starter-you gotta consider your starting/charging system on old vehicles when you do the arithmetic on saving the .6 .7 gph my 5.7 uses-your 454-wow-it might use 1gph at idle)
I have a scangauge-plug it into OBDII port-gives instant mpg or Liters per KM- rpms water temp-advance-load-throttle position(I think) lotta other stuff-also is a code reader. They won't work on the OBD1 you have-but would work on a 5.7 if you did a complete switch to a 96-99 5.7 or a 5.3 if you did an entire switch-ECM wiring harness-fuses-everything

I think it would be much easier to put a Vortec 96-99 5.7 in-even easier to put a TB 5.7(but they are waaay down in power vs 96-99)-than the 5.3-
But the 5.3-especially 2002 ( 2wd rated 13/17 EPA 2wd) or 2004( 2wd EPA 14/18) are inherently more efficient than the 96-99 2wd 5.7-12/17 EPA which my 1998 Suburban is-
But pretty sure the 5.7 will be easier to install-and thru 2003-the 5.3 and 5.7 have ALMOST the SAME EPA.2000 5.3 is the same12/17 2001 is 13/16 I think 2002 is 13/17-
The 2wd 2004 5.3 (EPA 14/18) is when the 5.3 clearly has a big edge-2 city 1 hy-MPG edge over the 96-99 5.7.
Now SOME of that might be aerodynamics-tires-some sort of tuning-never got clear answer on why the 2000 5.3 had same EPA as the 5.7??

My point-the 5.7's will give MOST of the mpg improvement of the 5.3-so something to consider(the earlier 5.3 had that funny piston slap like noise-didn't hurt the motors but hurt resale)
The 96-99 5.7's don't seem to have any quirks-teething problems-just the intake manifold gasket stuff-supposed to be cured with the latest FelPro fancy SS and silicone gaskets.

Yeah-you could certainly get better "not towing mpg" with the SBCs-maybe 3-4 mpg hy-2mpg city
You will probably miss that UMPH-of the 454-all accounts 454 nice tow motor
And gasoline is probably going to stay in the "nearly $4" range for a long time-our economy MIGHT be able to tolerate $4.50-so we can expect the speculators to drive up the price-especially if the chinese economy recovers from the little downturn they are apparently having.

Yes-GASOLINE-fuel- is going to be a real problem for most folks for a long freakin time-
On the bright side-in 10 months-62 ss- I'll have a little more $$-so I'll save my pennies and see if I can get a 2004 Suburban when someone foolishly sells or trades it for a crossover to get better mpg
Trying to look on the bright side of paying $4/gal- not much bright side other than lower prices on used 9 year old Suburbans!
Luck
Charlie