Better mpg out of my c20 454

[c20454]

I have a 1986 c20 silverado with a 454 v8 and a th400. It is stock except for Dual exhaust and I removed the smog pump. What could I do to get better fuel mileage, I love my truck, but the mileage kills me. I have considered doing a manual swap, how much would this cost? If that is impractical, how much could a overdrive 700r4 tranny help. Is there anything else I could do to at least get a couple more mpg.

[TheBigMortboski]

The 700R4 would be better, since you wouldn't have to get a clutch and fab a bunch of stuff up. They're very common, and you could probably pick one up cheap enough so that the better mileage would negate the initial cost of the tranny swap fairly quickly.

Aside from that, take as much weight out of the truck and drive like there's an egg under the throttle.

[DieselPower]

Tow it with a smaller truck. Only drive downhill. Walk more.

A 454 with a TH400... No overdrive, no lockup converter, probably geared for towing... You have a great recipe going for towing stuff, but probably one of the best drivelines ever put in to a pickup truck to make gasoline go away. You can spend a lot of time and money working to get a little better mileage out of it - all of which will compromise your ability to tow stuff, or you can accept the fact that if you are only going to have 1 vehicle, you are going to spend a fortune in fuel. Decide if you like the truck and need it's capabilities - and if a second, smaller vehicle is a practical route to take.

A 700R4 will help, but it won't tow like a TH400. If you are going to go that route, might as well look at a set of 3.08 gears for the diff. Forget towing, but it'll all help the fuel addiction. A 454 just really likes gas. A lot of gas. Skip the bit about the egg under the throttle, drive like your own testes are under the throttle.

[1988 GMC 355]

A set of longtube headers will help and really getting the carb tuned perfect is a huge thing, aluminum wheels if you have steelies and a OD tranny.

[Quyonmob]

What is your current mpg?

Gains of 10% would be impressive... which bumps mpg from 10 to 11... Which changes very little for you at the pump.

[BHB]

Does it have one of those electronically controlled Q-jet carbs? if so, is it still hooked up?

[TheBigMortboski]

If it has a Q-jet, just rig it up so the secondaries never ever ever ever open up. That'll help.

[c20454]

It has a Quadrajet with vacuum secondaries and averages about 10 or so depending if I can keep my foot out of it or not lol. Has anyone had experience with gear vendors? How much do you think gear vendors could gain me?

[Quyonmob]

Not enough to pay for itself unless you really rack up the miles.

[trickedout420]

i would say be happy with the 10..i have a 496 with the turbo 400 behind it and all i can say is i get 6 mpg on a good day..but i also have 37 inch tires and 4.10 gears...i would just see if your budget will allow you to get a smaller vehicle around $1000 for the better gas mileage

i searched craigslist for about 3 months and found an s10 with about 200k miles on it that didnt run gave the guy 100 bucks for it and all that was really wrong with it was a bad alternator

[dalaigh]

It has a Quadrajet with vacuum secondaries and averages about 10 or so depending if I can keep my foot out of it or not lol. Has anyone had experience with gear vendors? How much do you think gear vendors could gain me?
If you want to buy a gear venders overdrive, I suggest just spending that money on a small ecobox car, and drive the truck only when you need it.

If you don't tow with the truck, look into a 700r4, taller gears (2.73,3.08,3.42 or even 3.73's), tune or rebuild the q-jet, electric fans, lower the truck (lessens the wind resistance from under the truck), make sure the engine is running properly (i.e.; tuned, timed, and properly lubed). You could lean out the carb a bit and retard the timing, but it won't run as good as if it were timed to factory specs.

[454cid]

A NV4500 would get you overdrive, but I think they tend to be expensive. The other option would be a 4L80E with a standalone controller, but that would be even more expensive. If you could find a GMT-400 parts truck cheap, you could swap in the whole Vortec 454 and transmission combo, along with the wiring. I only get about 10mpg with mine, but it has about 225K miles and needs some work....... and it's 4wd with 4:10 gears. You could probably do better with a 2wd.

[1998454]

I wouldn't even consider the 700r4 unless it was built really well (expensive). In a heavy truck the 454 and 700 don't play well together and the 700 always loses.

[dalaigh]

I wouldn't even consider the 700r4 unless it was built really well (expensive). In a heavy truck the 454 and 700 don't play well together and the 700 always loses.
I've had 700's in a few trucks, one truck I would take off road and it had a built 350 (400hp at the wheels), that transmission had a shift kit, thats it. One I drove everyday with a 454, that 700 was rebuilt stock before I put the 454 in and it worked great for years, I put 80,000kms on that truck. The truck I have now, that is going to be my daily has a 700 and I'm planning on keeping it after I rebuild it (has 348,000kms on it). The trick with the 700 is if you are towing with it, keep it out of OD.

And to build one well doesn't cost that much, I plan to build the 700 I have now. I'm using the same guy that a buddy of mine used to rebuild his, and his truck runs great. He DD's, tows and off roads with his, and has put 20,000 trouble free kilometres on it. He supplied the trans and the build cost with parts was $1500. Used trans was $150.

[1998454]

I stopped using them in cars when i got ahold of an 80e. Had a mild 350 in a car and 700's stacked up like firewood. Had one decent 700, but broke a shaft internally behind a mild 454. I just posted that to the OP because the 700 is inferior in every way to an 80e. No doubt, a 700 will pull a truck around, but it will always be the weak link.
I've had 700's in a few trucks, one truck I would take off road and it had a built 350 (400hp at the wheels), that transmission had a shift kit, thats it. One I drove everyday with a 454, that 700 was rebuilt stock before I put the 454 in and it worked great for years, I put 80,000kms on that truck. The truck I have now, that is going to be my daily has a 700 and I'm planning on keeping it after I rebuild it (has 348,000kms on it). The trick with the 700 is if you are towing with it, keep it out of OD.

And to build one well doesn't cost that much, I plan to build the 700 I have now. I'm using the same guy that a buddy of mine used to rebuild his, and his truck runs great. He DD's, tows and off roads with his, and has put 20,000 trouble free kilometres on it. He supplied the trans and the build cost with parts was $1500. Used trans was $150.

[ashworth]

What is your current mpg?

Gains of 10% would be impressive... which bumps mpg from 10 to 11... Which changes very little for you at the pump.

Very true and I don't know anybody that really drives a BB for gas mileage.

[c20454]

Haha I'm not driving it for gas mileage. I guess I was just trying to find a way to justify keeping it, but at this point I think I'm going to sell it and buy an early 2000's chevy or f150 instead.

[ashworth]

buy the newer one and turn your c20 into a blown street rod... :)

[jaredself]

We don't have these pickups because that's all we have (for the most part). We drive these pickups because we like to drive them and, depending on gas prices, we'll probably still be driving them in the future...just not quiet as far.