Hypermiling with a carburetor

[SarkOzy]

Rick, did you ever pull that carb and rebuild it? Rebuild kits for q-jets are CHEAP and pretty easy to do with instructions. That would help more than anything else once the weather warms up and you drive it more.

[theholycow]

No, I've been too broke for even the cheap kits (which I don't think include the parts that are rotten on mine anyway, but still worth a try) and too scared to touch it. Every carburetor I touch only ever gets worse.

I may have to risk it, though, because it's getting pretty awful.

[SarkOzy]

Yea that'd definitely be the best thing to do for starters. It'd run so much better.

[VetteOwner]

yea sounds like you just need to rebuild your carb. my chevettes wasnt so hard. just go slow and record every part and screw you take off. take lots of pictures especially with linkages so you can get them back on the right way.

and the comment about ethonal gas, my 1980 chevette's owners manual says its OK to run E-10 fuel but no more. havent had any fuel related issues with it. id imagine if GM spent money making the chevette holley carb E-10 useable them im sure they would do it to the quadrajet in the more expensive cars...

[Jay2TheRescue]

They did that because there were a lot of stations selling "gasohol" in the late 70's during the energy crisis. When gas got cheaper, ethanol blends went away for the most part, but started coming back with oxygenated fuel requirements by the EPA.

[theholycow]

Originally Posted by VetteOwner

and the comment about ethonal gas, my 1980 chevette's owners manual says its OK to run E-10 fuel but no more. havent had any fuel related issues with it. id imagine if GM spent money making the chevette holley carb E-10 useable them im sure they would do it to the quadrajet in the more expensive cars...

Hmm...did it look something like this?


(From my car's manual.)

[VetteOwner]

lol pretty damn close haha.

[8$PG]

I'd suggest no engine breaking at all because the rpm is directly linked to the fuel consumption. Keep the rpm at idle if possible whenever no engine power is needed. Pretend the clutch has a freewheel.

[jcp123]

+1 on rebuilding the carb. Might as well figure out what jetting would be ideal as well - like my Carter AFB (basically what we know today as an Edelbrock Performer), you use metering rods, a nice setup to differentiate your cruise and power settings. I am not familiar with the minutiae of the Q-jets, but selecting the right rods will be critical. In my Carter, it's easy enough to swap out rods that I keep a set for summer and winter, swapping out when needed; I use the factory jets and selected my metering rods around that.

You're limited beyond that except for hooking up a vacuum gauge. If your cooling system works well, try upping your thermostat temperature - I went from the rebuilder's 160* unit to the factory spec 180*, you can probably get a 192* unit as well. Neutral glides and keeping speed down will be your friends. I was able to raise my Mustang's commute mileage from 14mpg to 17 this way - 3mpg doesn't sound like much, but on a percentage basis, that's pretty darn good.

[theholycow]

Yeah, metering rods should be pretty easy.

I bought a junkyard carb (matching numbers) to rebuild but the project kind fizzled out in my basement...I may resume before this "winter" is over. Anyway I've forgotten just how easy the metering rods were but I suspect they were easy enough to swap for winter as you do.

I have a vacuum gauge but the way I'd really like to use it is to avoid low-vacuum enrichment...unfortunately I don't know where it kicks in, nor do I know how to figure it out.

It's been so long since I was studying/working on it that I can't remember any of this stuff.