Gas mileage???

[Blake442]

If nobody local knows how to build a Q-jet properly, there's plenty of other people you can send it to that do.

My 350/TH350 powered '81 El Camino with a q-jet I used to have got 12-16 mpg depending how I drove it.
I'm expecting about the same from my Olds wagon since that is where the drive train is now...

My 267/TH350 powered '79 wagon with a 2-bbl got 19-22 mpg on average.

My 3.8/M200 powered '81 Buick wagon with a 2-bbl gets 18-20 mpg on average.
Yes, the V6 gets slightly worse milage than a V8 since it's working harder just to get up to speed. Depressing, I know.

When my 442 still had the stock 307 and 200-4R, it got 15-19 mpg, same with when it had the Chevy 350 in it.
Now that it has the 455/TH400 with a 850 Holley and 3.73's it gets anywhere from 8-14 mpg depending how I drive it. Usually closer to 8-10...

 

[pontiacgp]

I rebuilt it myself "Quadrajet Rebuild" thread

then don't take it back to the guy who rebuilt it....

one of the guys out of our shop is headed to mooresville today to meet with JR....if you can catch him drop the carb off with him and he'll get it done right..

 

[Oldsmoletick]

When I had 2.41's in the bu it was able to achieve 23-25 mpg on the highway, that was with the olds 350, RV type cam, aluminum intake, msd, 600 carter carb, and th350 non lock-up. Sounds like b.s., but I used to take it on road trips over my jeep just because it was so much more economical. Now that it has 3.73's I haven't dared to check my milage, and it stays close to home :lol: .

 

[dogsht]

12 to 17 mpg with an 800 Q-jet in an 88 Cutlass with a 509ci Cad, 200-4R, working lock up, 3.42 gears, (2.29 final drive ratio) & 28" tires. Send it to http://www.sparkyscarbs.com

Hey Oldsmotick, Get a good 200-4R and you should get the same mileage as you did with the 2.41s as you would have a 2.49 final drive ratio with the 3.73s. Get the lock up working in the converter and save another 2 to 300 rpms and you should turn almost exactly the same rpms on the highway. Plus you would not be spinning the snot out of your engine running down the road.

 

[gto78]

With that kind of mileage I'm guessing the carb is probably screwed up a little bit. Is your choke opening all the way? Does it smoke at all? Plugs clean or black? Do you run any emissions? Is there an exhaust valve on your car in the exhaust system that could be stuck partially closed, restricting your exhaust?

One summer I checked mpg in my Grand Am on the highway, with 400 pontiac, mild cam, headers/exhaust, no emissions, edelbrock intake, and a spread bore new style holley (one piece body/bowls). I was getting 14-15 mpg at 65 mph with 3.73 gears. I tried a standard square bore setup with different style venturis and my mileage dropped considerably, only 11-12 mpg on the highway. Partially to blame is the square bore vs. the spread bore, and also the better annular discharge venturis in the new style Holley carbs.

 

[Oldsmoletick]

Hey Oldsmotick, Get a good 200-4R and you should get the same mileage as you did with the 2.41s as you would have a 2.49 final drive ratio with the 3.73s. Get the lock up working in the converter and save another 2 to 300 rpms and you should turn almost exactly the same rpms on the highway. Plus you would not be spinning the snot out of your engine running down the road.

You know what really sucks? I had a 2004r out of an 86 or 87 MC ss that I shitcanned a couple years back, it supposedly worked too, this was before I knew that they could actually be built to handle abuse . My own stupidity....but I do have a 350C kicking around that I plan on rebuilding, along with knocking my rear down to a 3.42 (car is useless in first gear with 3.73's ), should put me back around where I want to be (cheaply too).

 

[DRIVEN]

My bone stock 305 w/Q-jet in my Cutlass gets 19-20 with a TH200 and 2.29 gears. I have been playing with the trans/rearend and the suspension but will resist the urge to touch the engine, aside from routine maintenance, until it suffers some sort of catastrophic failure.
My El Camino formerly had a 350 with World Products SR heads, Performer cam, stock '68 Quadrajet and iron intake. With the Muncie and 3.08s it got 16ish. Once I swapped in my MY6 (New Process overdrive A833) I got a best of 21MPG on a 550 mile trip hauling 800lbs + 2 passengers one way and no load on the way back. I haven't put enough miles on the new 415 engine yet to have any numbers on it.
Something is definitely wrong with your combo. Have you run this carb/engine before or is it a new build? Definitely check your timing. Be sure you have both mechanical and vacuum advance. Shoot for about 35* total all in by 3000rpm. Also check for vacuum leaks. Keep us posted. Threads with no ending don't teach us much :lol: .

 

[marcar1993]

My stock 307 gets ~15 mpg highway at 50-55. I think I'd do better at 65 though, because at 50-55 it kept shifting into 2nd gear (2.14 gears for ya ) and I was following someone so I couldn't speed up.

You want sad? My wagon has gotten a best of 12mpg highway... I avg 4-6 in town. If I get on it any I can dip into 3 mpg. That's what 5k lbs will do.
All this with a stock 2bbl 318.

 

[RITTER]

Alright, so my buddy brought his good timing light over and messed with my timing to 32* and he tested the vaccum system (I have never done this, so I didn't really know how) The car is still lacking a lot of power. I put the other quadrajet 17085210 carburetor back on it that I was running before the 17058213 rebuild, and a ton more power! The 17085210 Quadrajet has the dual capacity pump selenoid (which is not hooked up) and I have read that these get horrible mileage when not wired up because they constantly feed your engine as though it is cold. So the lack of power is definitely in the 17058213
Now back to the gas mileage topics:
As far as the choke goes, it is a manual choke, and I propped wide open to make sure it was open, and it acts the same.
I have not used this carburetor before I rebuilt it. The guy I bought the engine from said that it started to not run with that carburetoron it so they put the 17085210 on it (they gave me both with the engine)
I don't run any emissions. I run full long tube headers through true dual 2.5" exhaust with an X-pipe and THRUSH mufflers (no cats or nothing) I removed the plugs and they look good. It doesn't smoke at all, not even at start-up.

 

[Bonnewagon]

My wagon gets a solid 20 mpg with a 301 4 speed and 2:78 gears. Did you happen to note what jets and rods were in the carb you rebuilt? A quick check indicates that the 17085210 is from an 85' Chevy automatic. The dual choke wire I have only seen on a Chevy truck so I'm guessing it's a truck carb. All that does is bleed off some of the pump shot when the motor is hot. The last one I worked on like that had #71 jets and #49 rods IIRC and was on a 350 automatic. It should work fine on your motor. The 17058213 should be a 78' Chevy manual trans carb. It should be even leaner than a 73' carb would be unless someone played around inside. Perhaps someone "hotrodded" it and now it's way off.Since you now are a Q-jet mechanic why not open it up and check it out? Here is a link for deciphering Q-jet codes. http://www.cliffshighperformance.com/tech_carb_ID_2.html And here is a link to find out what SHOULD be inside the carb as it left the factory.http://www.newagemetal.com/