411 swap

[L31MaxExpress]

So basically OP needs to get rid of the big, heavy and non-aerodynamic box truck with an archaic pushrod engine and get a civic or similar? Or did I miss something?

OP: What is your MPG anyway? I'm trying to think of a modern vehicle for your needs that may give good fuel economy...I can't think of any.

I think a Ford Transit with the latest-tech. V6 gives mid teens MPG per the manufacturer. Around 14 city? I bet the real world is lower. Highway is a bit better it seems. I think that has to do with the fact they are unibody, and therefore, lighter than a frame-on-body equivalent. We know several families that have the Transits. One Dad told me they suck gas like crazy, but I didn't ask what the actual MPG was, or if he even knew.

My experience with the 8 lug Express vans is somewhere around 12 MPG, even the later ones. I drove a 2500 with a SBC 5.7 out of high school making window blind deliveries and drove it like I stole it (dumb me!) I recall 10-12 numbers. My neighbor is a paint contractor and his van has the 4.3/6 lug. I don't know what he gets, but probably the similar. We rented a 15 passenger once and drove to Georgia and I recall around the same MPG per the cluster reading, and loaded with people to the max.

Maybe the smaller turbo diesel engine equivalent full sized vans get much better MPG?

BTW, I don't think them Ford engineers got the Memo about NOT using pushrod engines on the latest 7.3 Godzilla engine for their newest F-250 thru F-650 medium duty line-up...

My 97 post 8-lug with the old 350 would get 18-19 highway with 3.73s and dropped to 17-18 with the Lunati hotcam and 5.13s. Pure city driving it went from 11-12 to 12-13 with the gears and bigger cam. Just don't have to use as much throttle to get rolling with the gears. Towing my travel trailer with the bigger cam and gears was night and day difference though. Bigger cam added lots of power in the 3,000-5,200 rpm range where you need it to accelerate or maintain speed on long grades.

When my 97 was practically new with the 4L60E and 3.42s we took a trip to Tennessee for a family reunion and went up to see the Corvette plant in Bowling Green and on to Cincinati. Back before the heavy ethanol dosing, the Express averaged 17.9 mpg for that trip and had a best tank of close to 20 mpg. I found the small notebook in the van recently where we hand calculated fuel economy for about the first 50K miles and kept track of the maintainence. Oddly enough the old 83 with the carb 305/700r4 and 3.08s always bettered it in fuel mileage probably due to the fact it was nearly 1,000 lbs lighter.

 

[stutaeng]

My 97 post 8-lug with the old 350 would get 18-19 highway with 3.73s and dropped to 17-18 with the Lunati hotcam and 5.13s. Pure city driving it went from 11-12 to 12-13 with the gears and bigger cam. Just don't have to use as much throttle to get rolling with the gears. Towing my travel trailer with the bigger cam and gears was night and day difference though. Bigger cam added lots of power in the 3,000-5,200 rpm range where you need it to accelerate or maintain speed on long grades.

When my 97 was practically new with the 4L60E and 3.42s we took a trip to Tennessee for a family reunion and went up to see the Corvette plant in Bowling Green and on to Cincinati. Back before the heavy ethanol dosing, the Express averaged 17.9 mpg for that trip and had a best tank of close to 20 mpg. I found the small notebook in the van recently where we hand calculated fuel economy for about the first 50K miles and kept track of the maintainence. Oddly enough the old 83 with the carb 305/700r4 and 3.08s always bettered it in fuel mileage probably due to the fact it was nearly 1,000 lbs lighter.

Well damn, I feel like I've been cheated all this time now!

A 2500 anything getting that high MPG is un-believable, unless it's a diesel...How did you manage to get HIGHER (18-19?) mpg than what the EPA rated them for? I think they were only rated like 17 mpg for highway, and everyone knows the EPA ratings from the 90s were overly optimistic. They still are, LOL. I think they rated them with AC not running and I can't remember what else? ...am I making that up?

Back in 2010 I was driving my ECSB 1500 2wd 4.3/3.42 Silverado to Houston for hurricane Ike assessments monthly and averaging about 3k miles almost every month (also did RGV for Dolly). I did check mpg a few times and if I stayed speed limit I got as high as 20.4 mpg. That's the highest I've gotten on the GM trucks I have owned (within rounding error of 20 mpg that was the EPA rating IIRC.) That was empty, no accessories on in the Spring time, pretty flat terrain. Only a small ladder, a small luggage case and me. From what I recall, that was about 1-2 mpg higher over the V8 option of the same truck. City driving is about the same for V6 vs V8...

Your TBI got better mileage than your Vortec? My brother and Pop's have a 88 & 90 RCSB 5.7 TBI. Brother's has a 3.73 now, but it originally had 3.08, not sure on Pop's ratio. I'll have to ask them, but I don't think either of them get anywhere near 20 (maybe 14?), and those trucks are as light as they came. My Pop's had an aftermarket Crane (or Comp?) cam when he bought it back in 2000. It sounded nice with some aftermarket muffler and had good acceleration, that thing was a gas hog! The engine eventually developed a knock and it got a junkyard replacement from a Suburban. Dad said it's still a gas hog...it doesn't get driven much. His tires get replaced after age and yet still have like 95% of tread life.

Back to question: As I've mentioned before, MPG is more of function of vehicle weight than anything else. OP has a box van, so I'm thinking he's got the heavier version of the vans and the aerodynamics of a semi. I seriously doubt he's going to get anything over 15 mpg combined driving.

 

[L31MaxExpress]

Well damn, I feel like I've been cheated all this time now!

A 2500 anything getting that high MPG is un-believable, unless it's a diesel...How did you manage to get HIGHER (18-19?) mpg than what the EPA rated them for? I think they were only rated like 17 mpg for highway, and everyone knows the EPA ratings from the 90s were overly optimistic. They still are, LOL. I think they rated them with AC not running and I can't remember what else? ...am I making that up?

Back in 2010 I was driving my ECSB 1500 2wd 4.3/3.42 Silverado to Houston for hurricane Ike assessments monthly and averaging about 3k miles almost every month (also did RGV for Dolly). I did check mpg a few times and if I stayed speed limit I got as high as 20.4 mpg. That's the highest I've gotten on the GM trucks I have owned (within rounding error of 20 mpg that was the EPA rating IIRC.) That was empty, no accessories on in the Spring time, pretty flat terrain. Only a small ladder, a small luggage case and me. From what I recall, that was about 1-2 mpg higher over the V8 option of the same truck. City driving is about the same for V6 vs V8...

Your TBI got better mileage than your Vortec? My brother and Pop's have a 88 & 90 RCSB 5.7 TBI. Brother's has a 3.73 now, but it originally had 3.08, not sure on Pop's ratio. I'll have to ask them, but I don't think either of them get anywhere near 20 (maybe 14?), and those trucks are as light as they came. My Pop's had an aftermarket Crane (or Comp?) cam when he bought it back in 2000. It sounded nice with some aftermarket muffler and had good acceleration, that thing was a gas hog! The engine eventually developed a knock and it got a junkyard replacement from a Suburban. Dad said it's still a gas hog...it doesn't get driven much. His tires get replaced after age and yet still have like 95% of tread life.

Back to question: As I've mentioned before, MPG is more of function of vehicle weight than anything else. OP has a box van, so I'm thinking he's got the heavier version of the vans and the aerodynamics of a semi. I seriously doubt he's going to get anything over 15 mpg combined driving.

My cruising afr is around 16.5:1 and I have driven through entire states without using the brake pedal.

 

[stutaeng]

My cruising afr is around 16.5:1 and I have driven through entire states without using the brake pedal.

I was thinking completely stock vehicles...

Will adjusting the tune work for OP in California with all the SMOG regulation stuff? They seem pretty stringent with tunes and aftermarket stuff, as was mentioned earlier.

...and OP never bothered to check back on the thread, so maybe it wasn't his top priority, LOL.

 

[L31MaxExpress]

I was thinking completely stock vehicles...

Will adjusting the tune work for OP in California with all the SMOG regulation stuff? They seem pretty stringent with tunes and aftermarket stuff, as was mentioned earlier.

...and OP never bothered to check back on the thread, so maybe it wasn't his top priority, LOL.

Easy fix there. Tuned PCM and a Stock one. A few weeks before smog, swap the stock one back in.

 

[Erik the Awful]

A 2500 anything getting that high MPG is un-believable, unless it's a diesel...How did you manage to get HIGHER (18-19?) mpg than what the EPA rated them for? I think they were only rated like 17 mpg for highway, and everyone knows the EPA ratings from the 90s were overly optimistic.

I think we have unrealistic expectations of how much time and energy actually goes into optimizing fuel mileage. The manufacturers would like us to believe there's a team of a hundred engineers poring over data and running tests, every day. In reality there's one lead engineer trying to wrangle half a dozen other engineers - who would usually rather be doing something else. If the accountants aren't demanding fuel mileage increases, the engineers are trying to find out if they can use a smaller cheaper bolt to hold the crank pulley on, because if they can save the corporation $100,000 on half a million bolts they might get a $100 bonus. Always remember, the world is run by C students, because "Cs get degrees".

 

[stutaeng]

"...in architecture: B-students teach, and A-students work for C-students."

That was one of the few things I remembered from that introduction college course professor...

Turns out it's true.

 

[0xDEADBEEF]

I agree that OEMs are in some ways limited in what they can do, but they have much more resources than 7 engineers working on it. We're in the modern age of modeling and CFD.

 

[L31MaxExpress]

Also as I mentioned the OEMs need to be able to pull any vehicle at random and have it pass emissions requirements, sound decibel requirements. Means the tunes have to be tailored to emissions, not mileage or power and have to work across the board with varying degrees of production tolerances.

 

[L31MaxExpress]

"...in architecture: B-students teach, and A-students work for C-students."

That was one of the few things I remembered from that introduction college course professor...

Turns out it's true.

That is true! When I was younger I was an A+ student. When I got into middle school I was an A- and B+ student for the most part and maybe a C in english. In high school a B or C student and failed a trimester of spanish that I had to re-take. I had decided I wanted to work around vehicles. I went to trade school and started in the automotive world. I have been a dealership parts manager, managed a big chain retail parts store, ran a dealerships parts counter as a lead over a group of counter guys, and have been a senior service advisor aka service drive manager over a group of other advisors. So I guess it holds true.