1976 2wd Blazer with 350- Better Milaage Ideas?

[CircusWagonJim]

I have a bone stock '76 2wd Blazer with the original 350 V-8 and granny low manual 4-speed and 3.73 rear gear. The thing runs perfect, but only gets 9mpg on the highway! I know the factory carb is flushing the gas. Will a carb swap help substantially? Edelbrock? Is there a more user friendly transmission I can put in place of the stump puller? 3speed, 4speed or 5speed? Will I ever see 20mpg with the right changes? I'm open to suggestions. Ignition- Pertronix?

[Ziegelsteinfaust]

I would start with a rebuilt qjet, and have it done by a pro. My c20 got better mileage doing 65 with a dead motor. You should be around 14 cruising 65. The qjet is the best carb for mpg, and yours is probably pouring fuel.

If I were you I would look at a nv4500 for a trans. I think that is the truck 5 speeds name. If you do not have a hei get one with 8.8 wires, and do a full tune while at it.

Depending on the condition of your motor, and how much your willing to fix. 20 mpg is about the limit in these old trucks with out really going overboard. I have gotten 22, but it was a full build with mpg as the goal. An ls swap can be good for 25mpg as part of a whole concept build. I mean keeping rotational weight low, and torque strong. So no big rims and tires. Plus keep tread ware high.

[CircusWagonJim]

The orig carb is better than a new Edelbrock with small secondaries? Any idea how hard a manual 5-speed swap is? It has an OD gear I hope? I am swapping to smaller new tires. Not into the off road look.

[andrewmp6]

I would start with a full tune up and maybe rebuild the carb on it.If you have to swap trans look in a t5 or if you got money to burn a t56.

[geezer#99]

Maximize your timing.
Adjust the apt on your carb to the leanest spot.
Remove all un-needed weight.
Install a vacuum gauge and always drive to the highest vacuum.
Put on taller narrower tires.
Only drive 55 mph.
Accelerate and decelerate slowly.
Drive like you have an egg under the pedal and you don't want to break it.

[rich weyand]

Yes, the Qjet is better than the Edelbrock for mileage. Smaller PRIMARIES is what you want for mileage. Smaller primaries means a higher stack velocity in the barrels at cruise, which gives better atomization.

Oh, and you need a new or properly rebuilt Qjet. They leak gas when they get old. Talk to Sean at SMI Carburetors. Google it. Generic Qjet won't work -- they have a lot of little air bleeds and such that have to be set up right. He will build one for your setup for no more money than generic.

All of the suggestions above are good ones. You might also move your vac advance to unported (manifold) vacuum, and see how far you can advance the timing without getting knocking. 12 BTDC base timing anyway. I'm running 17. Big difference. You probably have to swap the vac advance back whenever you do emissions testing.

[CircusWagonJim]

Excellent! Thanks!

[rich weyand]

Tires will also make a big difference, as noted above. You want tires with less rolling resistance. Most A/T tires have high rolling resistance, so you want highway/touring tires.

This is the only low-rolling-resistance tire I found on tirerack. Dunno if anybody on the forum is running these.
http://www.tirerack.com/tires/tires....d&autoModClar=

[Edahall]

A 2.73 rear end would also help get better fuel economy. With your 4 speed manual, 4th gear would be like overdrive. 1st gear would become functional. You just won't be able to tow anything.

[rich weyand]

Agree on the 2.73:1. Another option is to put shorter tires and/or wheels on it, and then correct the speedometer. Cheaper than a differential change, but for 2WD the differential change isn't that bad.

2.73:1 on stock 29" tires will give you about 2000 rpm at 60 mph. If you regularly cruise at 70 on the highway, you might even be able to go to an even higher ratio, like 2.29:1. That would give you about 2000 rpm at 70.

[killthewabbit]

Wow, I haven't thought about the Circus Wagon truck in ages.

Good luck, man

[CircusWagonJim]

Yep, that was mine.

[motornut]

What choke do you have?
If it's vac pull off I'd tie off the choke.
Chances are if it's that style, and if your finding vacuum leaks,gas mileage will drop.
Easy way to check.

[gchemist]

If I can get 18 MPG with a 355 HP motor carbed, you can hit 20 MPG @<65 MPG with an LS 5.3 conversion.

[D13]

You will NEVER get that box to 20mpg on the highway with a 350. 13-15 would be good. All the stuff about leaning it out and bumping timing, etc, is good, will give a little better mileage, but assuming the truck runs well now, not much is to be had witout decreasing the fun content. A motor on the lean edge with fully advanced timing for daily driving wil not like to tow (whihc is what your truck is set up for).
Swap to 3.08 gears. This is the only major mod that will return its cost in fuel savings.
When you need tires go up 1 size in diameter and 1 size narrower, ie from a 235/75 to a 245/78 or even better, 235 /85.
IF you could find a complete a833 there is some gain to be had, but note that the 2wd version would be marginal behind a 350. You could swap in a 5 speed but $$ and you would have to look at the payback.

Drive very gently is the #1 improvement. I can make 10% change in fuel from normal to economy mode of driving.

5.3 is great but someone would have to give it to you, or you would have to drive a lot of miles, before the economics work out. But man are they fun.