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Username Post: Best carburetor for daily driver?        (Topic#156828)
doesGO 
Member
Posts: 42
doesGO
Loc: Los Angeles
Reg: 04-23-04
04-12-07 11:06 AM - Post#1141323    

Hello all, I have a question and please dont mind me asking this.

I drive my Nova daily and the gas prices forcing me to make it more fuel efficient since now instead of getting new parts I'm spending money on gas..:(

Right now I run an Edelbrock Q-Jet Series Carburetor - 4MV - 750cfm (part # 1901) which gives me about 12-13 mpg. Is there an even better one that would give me about the same performance but better gas mileage?

I should mention also that I'm planning to install an electric fan and MSD ignition system in the near future.

Please advice,

Thanks!

Las

 
sgian 
Valued Contributor
Posts: 4551
sgian
Loc: MO
Reg: 12-25-03
04-12-07 07:10 PM - Post#1141709    
    In response to doesGO

Not likely unless the qjet needs to be rebuilt anyway. The Edelbrock Performer is just an updated version of the Carter AFB from the 50's and the common Holley carbs are also older performance oriented designs. The qjet began replacing the Carters and Holleys in the late 60's because it is a better carb for gas mileage and emissions than those older carbs, but it still has the big secondaries for adequate performance. Holley took the qjet design and made the Economaster, which is only around 450 cfm and might get better gas mileage than the qjet because it doesn't give as much WOT flow. Don't worry about the 750 cfm rating of a qjet, when calibrated right it will not flow any more than the engine can handle because of its more advanced design (the secondaries have a better system for reacting to vacuum than the older carbs). Even TBI isn't better at gas mileage than the last qjets it replaced, if you compare 86 Suburbans to 87 Suburbans (when TBI began being used), the 86 Suburbans with an electronic qjet actually got slightly better highway gas mileage than the 87 TBI Suburbans. The trucks got a body style change in 87 so they aren't a good comparison between 86 and 87.

Now if the qjet is worn out or has a problem, then replacing it with another type of carb may help if you are good at tuning them. But then of course fixing or replacing the qjet with a good qjet and tuning it right would also increase gas mileage. An Edelbrock 1901 should not be worn out by now since they aren't very old. Guys who are really good at tuning Performers (they are easier to fine tune) seem to be able to get as good gas mileage as people who throw qjets on their engines without doing anything more than adjusting the idle mixture. Now if someone was good as good at tuning a qjet for a specific engine as some of the Performer guys it would interesting to see the comparison...

Now if you are looking for performance without worrying about gas mileage, than the Performer and Holley are good alternatives.

Other factors may help with gas mileage more. Driving habits, the routes you take, ignition tuning (stock tuning is for primarily emissions and economy is secondary), modifications to the engine or drivetrain, etc can all affect gas mileage. With a 1901 carb on a 350 with a TH350 and 2.56 gearing (bad setup for city driving) I used to average 15-16 mpg around town when I had a 5-10 mile one way commute (I was trying to get up to 17-18 average around town). Now with a 1-2 mile commute mostly at 20 mph with lots of stops I get around 11-12 mpg; all of my vehicles have significantly dropped in gas mileage with this type of driving (even my newer vehicles avg well below their EPA ratings around here). If you can, try to find a route that has a steady flow over around 35 mph.

One way to go is to get a vacuum gauge and adjust the mixture with that. Make sure both screws are the same number of turns out (otherwise one side will be leaner than the other), then lean both screws the same amount in until the vacuum drops. Then adjust them back out until it just reaches the highest stable vacuum reading. Some people also benefit from mounting a vacuum gauge in their dash (JC Whitney sold them last I looked) and adjusting their driving habits to the gauge readings. Also look at your vehicle setup (CR, DCR, cam rpm range, and normal driving rpm), and make sure they all match. Keep in mind that performance upgrades don't always increase gas mileage, and especially when there is a mismatch they can drop gas mileage. I also have a somewhat controversial way of custom setting timing for each specific engine that has caused some arguments over in Performance, if you are interested in hearing it. It has gained me several mpg.

I have an MSD system in my Nova, and can't really say it was worth the money. The best thing I can say about MSD is that they make it really easy to precisely setup a mechanical advance curve. I can't say that the MSD-6A box, blaster II coil, and MSD 8360 distributor in my Nova is any better than the MSD HEI in my truck.

If you get an electric fan and it runs a lot, you might need to also upgrade your alternator to a higher amp 12SI or similar alternator. Outside my MSD system and a cd player, my Nova's electrical system is stock and I had problems generating enough electricity to have my stock A/C running with the stock alternator at idle (the extra load affected the idle even when tuned for the A/C running and wore out the stock alternator when I moved to AZ and got the A/C working again).
90 C1500, 05 Tahoe 4WD


 
doesGO 
Member
Posts: 42
doesGO
Loc: Los Angeles
Reg: 04-23-04
04-13-07 03:02 PM - Post#1142217    
    In response to sgian

Hi, thanks for replying with such detailed description.

Right now I'm fine tuning the carb and at this point I think I got it to a pretty solid state. I don't smell the gas anymore and the engine runs smoothly. I will get a vacuum gauge to be able to make an even better adjustments. I decided to keep my Q-Jet and become an expert tuning it. I keep hearing that its a great carburetor as long as its tuned right.

Thanks again...

-L






 
sgian 
Valued Contributor
Posts: 4551
sgian
Loc: MO
Reg: 12-25-03
04-13-07 06:54 PM - Post#1142380    
    In response to doesGO

The most likely way to beat a qjet in gas mileage without losing performance would probably be to get one of those multi-point efi systems, like from Holley or GM.
GMPP Ram Jet (minus ECM and vortec heads) http://store.summitracing.com/egnsearch.asp?N=700+...
Holley Commander
http://store.summitracing.com/partdetail.asp?autof...

Or you can put a 250 L6 into your car (stay away from the later integral heads because they crack). If you shave the heads to increase the CR and put a slightly bigger cam in it, you should be able to get around 200 hp and decent gas mileage (depending on your gearing). I have one combination I was planning (for a 78 Nova with 2.73 gears and would have included a swap from the stock 3-speed manual to a 4-speed Saginaw with a lower 1rst gear) that was desktop dynoed around 200 hp, if you are interested in the details.
90 C1500, 05 Tahoe 4WD


 
doesGO 
Member
Posts: 42
doesGO
Loc: Los Angeles
Reg: 04-23-04
04-17-07 11:22 AM - Post#1145049    
    In response to sgian

I like the combination so I think I will stick to my 350 and q-jet. After cleaning and using the vacuum gauge I made noticeable improvements in the gas mileage and also performance. I noticed the respond time so much quicker from take off as before it felt like I'm towing a 5 ton trailer. I'm still testing the gas mileage but I already have a new record of 14 mpg.

So I'm very happy with a results and thanks again for the tips I got from you guys.



 
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