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tbi 454 mpg

B

black dawg

1/2 ton status
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montana
My 91 burb (v2500 465/3.73s/stock hieght and tires) has been getting 12 highway 10 hills/city. When I first did the 350 to 454 swap I was happy with this mpg, but I have been driving this thing alot more than expected. This mpg is driving pretty slow (60-65).

any Ideas to get a little more out of it? I have a set of headers that I have been too lazy to put on, would they help much?
 
I dont know what else can be done my 79k10 longbed with a 350 Carb, 32x11.5 tires 3.73 gears averages 12mpg( I do have headers) but honestly we drive big heavy trucks with an older American V8s
I dont know how much more can be done
 
You're not going to make any huge gains. Best things you can are to make sure the rig is tuned up, has sufficient tire pressure, and isn't carrying around any excess weight.
 
and it is not that I think that mpg is poor (for the vehicle combo) it is just that I find myself using my diesel pickup that only costs slightly less to drive, when I would rather be driving the burb.
 
Pfft I wish I could get 12 ever!

My V3500 gets 7-8 everywhere. Ive driven it slow and nice and loaded on the freeway at 65-70 it still gets the same.
 
Your probably getting the best MPG it'll deliver ,really..but it would not hurt to make sure its tuned well and see that the thermostat is working,letting it warm up quickly and stay at 195 degrees..

A friend with a 90's 454 dually he bought new noticed a drop in mpg after about 20k on it and he found it needed a thermostat,it was sticking open so it warmed up slow and barely reached 165 degrees in city driving..it also had a O2 sensor that was "lazy",but did not set off the CEL or set a code..replacing both brought his mpg back "up" to 13 mpg,better than the 5-8 mpg he was getting..when it was new he got up to 15 on long trips with it,empty..He thinks putting smaller load range C tires on it VS the stock "E" rated ones may have reduced the mileage too,they probably have higher rolling resistance and brought the rpms up a tad..(he compensated for the speeometer being thrown off by the different sized tires too)..
 
should have mentioned, engine has around 30k now, stock 76 short block with vortec cam and 781 heads.

I never had the heads off, but I assume this is 8:1 or less. I wonder how much getting the comp up to 9.5 or so would help?
I think maybe Im just bored with the thing and want to do some cool stuff to it.
Also, I hear about all these ls swaps, and how much better mpg wise they are, but I have yet to see any numbers.:dunno:
 
My Dad's TBI 454 with headers, mild cam, Edelbrock intake, 465/GV OD unit/4.10's/~33's will get about 12-13MPG on the freeway. I don't think you'll see much better than that.

No matter how much money people spend on whatever parts for these trucks, aerodynamics seems to be the #1 killer of MPG. It's not weight, it's not height (to a degree), it's aerodynamics. 6.2L diesels will get up to around 25MPG, best gas figure I've ever heard that I think is accurate is 19MPG, and even that is upwards of "normal" for a 350.

As to the LS series, I'd have to revisit numbers (and I'm about to get flamed for saying this) but it didn't seem to me they were a whole ton better in the HP department than what a well-thought out 5.7L will do, although you can't directly compare, since the displacements (stock) aren't the same. Obviously the design overall and induction is different, but even ignoring those differences, I didn't think the 5.3L was "all that" compared to the marginally larger 5.7L.
 
Laughed at the subject line.

Really, thats pretty good. I barely get that with a new 350 in my 91 v2500 burb.
Blown away you are getting that with the 465.
 
Always check the little things, they can make a big difference. Mine's carb'd, but when I first got it, the choke wasn't working properly, the timing was off, and the fuel mixture switch was unplugged. Fixed all that and the truck went from about 5-6 to 12-13 in mixed driving. I have no illusions that I'll see much more than that, unless I start limiting my driving to downhill highway grades.
 
dyeager535 said:
My Dad's TBI 454 with headers, mild cam, Edelbrock intake, 465/GV OD unit/4.10's/~33's will get about 12-13MPG on the freeway. I don't think you'll see much better than that.

No matter how much money people spend on whatever parts for these trucks, aerodynamics seems to be the #1 killer of MPG. It's not weight, it's not height (to a degree), it's aerodynamics. 6.2L diesels will get up to around 25MPG, best gas figure I've ever heard that I think is accurate is 19MPG, and even that is upwards of "normal" for a 350.

As to the LS series, I'd have to revisit numbers (and I'm about to get flamed for saying this) but it didn't seem to me they were a whole ton better in the HP department than what a well-thought out 5.7L will do, although you can't directly compare, since the displacements (stock) aren't the same. Obviously the design overall and induction is different, but even ignoring those differences, I didn't think the 5.3L was "all that" compared to the marginally larger 5.7L.
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Honestly the LS advantage comes from being able to tune the MPFI better than older systems and head design. Throw an aftermarket MPEFI system with a good set of heads on a 350 and you can get the same MPG's. Squeezing MPGs is all about that computer tune for part throttle lean driving. Using as little fuel as you can when your just on the gas not asking much from the motor than to drive down the road.
 
If you are getting a real 12 mpg congratulations. You aren't going to see a ton more with a big block. Most people that I've seen only get 8-10 at best. My built 350 gets about 10-12. And that's babying it and trying not to go more than 1/2 throttle. It's hard to get better with the 465 trans and 205 transfer. Lots of extra weight and all gears. Losing weight will help if you have stuff in the back like I do as well. It's hard to make a big square box get any real huge gains in mpg. The 5.3 has been a great swap for a lot of people. It seems to get a few mpg better than most stock engines. But I couldn't see going from a big block to that. A good tuned injection unit will run better than a carb and net a few mpg in most applications that I've seen.
 
chulisohombre said:
If you are getting a real 12 mpg congratulations. You aren't going to see a ton more with a big block. Most people that I've seen only get 8-10 at best. My built 350 gets about 10-12. And that's babying it and trying not to go more than 1/2 throttle. It's hard to get better with the 465 trans and 205 transfer. Lots of extra weight and all gears. Losing weight will help if you have stuff in the back like I do as well. It's hard to make a big square box get any real huge gains in mpg. The 5.3 has been a great swap for a lot of people. It seems to get a few mpg better than most stock engines. But I couldn't see going from a big block to that. A good tuned injection unit will run better than a carb and net a few mpg in most applications that I've seen.
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I read of a guy running a 555" BBC in a stingray that went from a VERY dialed in 1050 dominator getting 10-12mpgs over to a holley dominator TBI system and is now getting just shy of 17. I know vetted and a suburban are apples and oranges but damn that's more than a 25% improvement.
 
chulisohombre said:
If you are getting a real 12 mpg congratulations. You aren't going to see a ton more with a big block. Most people that I've seen only get 8-10 at best.
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If I drive mostly highway, I see from 11.8-12.2

it doesnt take much driving in the hills to bring it down to 10.

driving to where I hunt is 150 miles round trip with 50 on mountain roads. last year making this trip 10 times, overall mpg was 10.5

running around the state this summer with lots of highway and some gravel mpg was right at 12
 
Just going to echo what everyone else has already said. a TBI 454 isnt going to do much if any better than 12ish mpg.
 
black dawg said:
If I drive mostly highway, I see from 11.8-12.2

it doesnt take much driving in the hills to bring it down to 10.

driving to where I hunt is 150 miles round trip with 50 on mountain roads. last year making this trip 10 times, overall mpg was 10.5

running around the state this summer with lots of highway and some gravel mpg was right at 12
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Same 454 was getting 5-8MPG cruising around logging roads hunting. At 10 MPG the small block drinks a lot of gas when you are off the pavement, the solution for me/us is to bring a trailer with a full ~100 gallon (more like 85 gallons all said and done) semi truck tank mounted to it. Saves more than a little time/hassle driving back out to get gas every few days.
 
Stomis said:
I read of a guy running a 555" BBC in a stingray that went from a VERY dialed in 1050 dominator getting 10-12mpgs over to a holley dominator TBI system and is now getting just shy of 17. I know vetted and a suburban are apples and oranges but damn that's more than a 25% improvement.
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That would be awesome to have that much power and cubes and still get 17 mpg. My 94 5.7 tbi gets 15-17 mpg stock 265/75r16 tires. Pretty sure that's average for a one of those. I'd love to have big block power and get the same mileage.aerodynamics would still drop that a couple mpg in a blazer or more in a burban but still would be nice to see.
 
I have been putting off either getting this thing tuned or getting set up to tune myself. Anybody have any experience with lean cruise with a big block?

I suppose I am losing some mpg to not having an egr intake?
 
I doubt you are losing much without EGR. Theory is all over the place on EGR/economy, but on my rig, carbed before, now FI, there seems to be no change in economy with or without EGR. At least not enough to notice.
 
The 88 Burb I recently sold had a 454TBI with "touched up" peanut port heads, Comp roller cam conversion including roller rockers, Thorley Tri-Y headers, 2.5 inch true dual exhaust, Edelbrock TBI intake, Enlarged Throttle body bores, matched injectors, salad bowl and 9-1 compression. With 4.56 gears, 4 inch lift and 35's and a 700R4 trans, she got 8-9 mpg around town and 10-11 on the highway. By comparison, my 2013 Tahoe Z-71 with 5.3, 3.42 gears and 31 inch tires gets 13 around town and 16 on the highway. The 2011 3/4 ton Burb I had with the 6.0 and 3.73's got 9-10 around town and 12-13 on the highway. Same driver, same routes traveled, real numbers for comparison.:thumb:
 
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