1991 Chevrolet C1500, the gas saver

[TravisR]

My 1993 SCSB Stock had 5.7L NV3500 MG5 10bolt 8.5 ring with 3.08 gears and 235/75R15. Got 18 MPG empty truck.

Currently, it has the stock 5.7L swapped NV4500MW3 with Gearvendors under/overdrive 14bolt SF 9.5 ring 3.73 gears and 245/70R17 aluminum Yukon rims from a 2007. My best now is 19.5 empty truck.

That gearing is going to make a big difference. 3.08 is tall gearing and was probably the main reason you got 18 mpg. My 5.7 has 3.73 with a stock 700R4, so it only gets 14 mpg.

On top of good mpg, a really long range is interesting to me. I remember my old 4.3/5spd got something around 400 miles per tank. It was a short bed, so it had the smaller gas tank. I've always wondered what a 4.3L, 5 speed, long bed with the big tank and 3.08 gearing would get. It would be cool to go 500 miles between fill ups!

 

[evilunclegrimace]

The intake is much more improved as well. It also has hypertonic aluminum pistons and aluminum heads.
17 city and 20.5 highway (from the DIC(Driver Information Center)


What are hypertonic pistons?

 

[Blackwater]

That gearing is going to make a big difference. 3.08 is tall gearing and was probably the main reason you got 18 mpg. My 5.7 has 3.73 with a stock 700R4, so it only gets 14 mpg.

On top of good mpg, a really long range is interesting to me. I remember my old 4.3/5spd got something around 400 miles per tank. It was a short bed, so it had the smaller gas tank. I've always wondered what a 4.3L, 5 speed, long bed with the big tank and 3.08 gearing would get. It would be cool to go 500 miles between fill ups!

I also have the Gearvendors behind the tranny. when active its like changing the diff gears to 2.91.1, that's about a 600 RPM difference accordin to my tack when switching from 5th to 5th plus GV or Double OD.


Aluminum alloy Pistons which gives it a higher temp rating and weight reduction.

 

[Blackwater]

@TravisR I'm starting my LQ4 402 stroker soon and thought about after the swap I can do a 3.42:1 gear swap since my first gear in my 2004 NV4500 tranny is 5.61:1. Then I can use the regular 5th for the 55mph drives and Double OD for my 65ish to 70mph plus drives. Im at 2000rpm at 70mph in double OD. The gear change is only 10%. I still will be starting in 2nd, I just won't be able to put it in first at idle (750Rpm) and jump out the truck, jog around it and jump back in. Red circle in the picture is 2004 NV4500 MW3 and the blue one is Gearvendors.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[TravisR]

@TravisR I'm starting my LQ4 402 stroker soon and thought about after the swap I can do a 3.42:1 gear swap since my first gear in my 2004 NV4500 tranny is 5.61:1. Then I can use the regular 5th for the 55mph drives and Double OD for my 65ish to 70mph plus drives. Im at 2000rpm at 70mph in double OD.

This sounds like an awesome set up for pulling and top end fuel economy.

 

[evilunclegrimace]

I also have the Gearvendors behind the tranny. when active its like changing the diff gears to 2.91.1, that's about a 600 RPM difference accordin to my tack when switching from 5th to 5th plus GV or Double OD.



Aluminum alloy Pistons which gives it a higher temp rating and weight reduction.

Ah, I see. I believe that you mean Hypereutectic pistons.

 

[Echomirage]

@TravisR I'm starting my LQ4 402 stroker soon and thought about after the swap I can do a 3.42:1 gear swap since my first gear in my 2004 NV4500 tranny is 5.61:1. Then I can use the regular 5th for the 55mph drives and Double OD for my 65ish to 70mph plus drives. Im at 2000rpm at 70mph in double OD. The gear change is only 10%. I still will be starting in 2nd, I just won't be able to put it in first at idle (750Rpm) and jump out the truck, jog around it and jump back in. Red circle in

i get why youre doing all the work, but if you want pure money savings, how much gas could you have bought for the price of the overdrive unit? how long will it take to make that money back in mileage?

if youre doing it as a project, then sure, do whatever you want. but if youre looking purely at a cost savings point, then it sounds like the people who fell for the clunker scam a few years ago. turned in perfectly good old vehicles to buy new cars they couldnt afford, just to get better mileage. yet when you factored in the cost of a new car, or the monthly payment, more insurance, taxes, etc.....you couldve bought a years or more worth of gas for your old vehicle, and still come out ahead.

 

[Blackwater]

This sounds like an awesome set up for pulling and top end fuel economy.

It is. but like I said before, the cost of the parts doesn't make up for the fuel savings. Its the fun factor.

Ah, I see. I believe that you mean Hypereutectic pistons.

I may have misspelled it. I'm not English Major. If I cant spell the word or find it in the dictionary I avoid it all together if possible.

i get why youre doing all the work, but if you want pure money savings, how much gas could you have bought for the price of the overdrive unit? how long will it take to make that money back in mileage?

if youre doing it as a project, then sure, do whatever you want. but if youre looking purely at a cost savings point, then it sounds like the people who fell for the clunker scam a few years ago. turned in perfectly good old vehicles to buy new cars they couldnt afford, just to get better mileage. yet when you factored in the cost of a new car, or the monthly payment, more insurance, taxes, etc.....you couldve bought a years or more worth of gas for your old vehicle, and still come out ahead.

Yes, it is a project. Yes, it has low gears for towing, a second tranny for towing options and it gets better fuel ratings at the same time. I could have kept the original differential and have 3.08:1 and rally save gas. It started by my NV3500 kept going and I wanted more power. So I thought, what can I do to make it better? Then I ran into a problem. The NV4500 4x2 has a solid yoke. The 4X4 has a slip yoke. The truck is 4X2. Also, what is the next weakest link? Rear diff. So then I got to thinking how to link it all together. cant put a solid yoke to a solid yoke.

 

[TravisR]

Here's an update on the C1500:

• Got the salvage yard 4.3 in
• Finally got to the point of starting it up
  • It wouldn't start. It would crank and crank but not fire up. I had spark at the spark plugs. I hooked up a fuel pressure tester but it would only read 0 psi.
  • I didn't like the looks of the ground cable, so I bought a new one. The truck fired right up!*
  • Fuel pressure gauge read 0 psi the whole time. Maybe it was a stuck valve on the gauge? I moved on since it is now running.
• Tonight I'm going to buy a new belt tensioner (the belt is loose, hopefully that's all it needs) and some vacuum line for all the 27 year old plastic I broke while in there.
• I may need a new oil pressure sender since it pegs out the oil pressure to the max when running.
• When I let off the clutch after starting I hear pretty heavy whining from the transmission and the RPMs drop by about 100. Not sure what this is...

*It turns out that a bad ground cable has been the problem multiple times for me on two different trucks. It's crazy the symptoms a truck will show just from not being grounded properly. I've had a no crank, a low oil pressure, and a crank/no start all from bad grounding.​