Improve mileage 350 with Quadrajet
 

Hi there,

see my sig for my ride.

I am trying to improve the mileage as much as possible.These are things I have done till now:

- replaced a continuously running cooling-fan (made a hell of noise) with a Flex-fan
- replaced bad spark-plug-cables by new ones
- replaced an open air filter under the hood by a cold air intake from behind the grill

All this stuff is supposed to improve the mileage of my car, but it hasn't improved one bit.

We drive about 60% highway 55mph and 40% city 30 mph. highway rides are all about 8-12 miles per event and every now and then a longer ride of 20-30 miles.

Our average mileage is about 6-6.5 mpg and I think we can do a bit better...

SO....what to do? any advise?

Re: Improve mileage 350 with Quadrajet
 

What's your timing set at? Increase it to 12 degrees initial and make sure your vacuum advance is working. Check the air pressure on your tires. Low pressure takes more power to move down the road.
Your cold air intake is good for power when it's hot out but you need warm air into your carb. Cold air and fuel don't mix well when it's cold out. A factory air cleaner with heat supplied from the exhaust manifold works well.
You're driving a heavy truck. Pretend there's an egg under the gas pedal and you don't want to break it. LOL!!!
Plan your trips. Find the route with the least stops and starts.

Re: Improve mileage 350 with Quadrajet
 

You probably have an electric quadrajet on you model, with all of the emissions garbage, unless you have removed it, and I doubt that thing is helping much.

Wires could have helped, but that would have been a very minimal increase if any.

Im curious about your cooling fan, you removed always running electric units? Or the stock clutch fan? The stock clutch fan would probably have been better as far as mileage.

Your ignition timing could have an affect on gas mileage, but I would guess if someone wanted to get real serious, I'd probably go about it as follows myself.

If you have the electric quadrajet trash it, and replace it with an older model, or for easier tunability, I'd go with a vacuum secondary Holley 650. You might get better milage with a well tuned older quadrajet, but there is definitely more work involved.

Trash the smog pump, and all emissions crap, disconnect the factory connection for the lockup converter in your transmission if you have one, and install an aftermarket trigger.

Buy a air/fuel ratio gauge, which works off of one or more O2 sensors, wideband better, and tune your engine to the best air/fuel ratio, so youre not running too rich and wasting gas.

Other than that, it just depends on how you drive also, and once you reach a good air/fuel ratio, there isn't much more you can do besides gearing.

Edit: your HEI distributor would need to be swapped for an older model also, if you have the elec quadrajet, and emissions crap.

Re: Improve mileage 350 with Quadrajet
 

Don't ditch your EGR it increases mileage, make sure it is working properly. Free flowing exhaust will help some too.

Re: Improve mileage 350 with Quadrajet
 

wow guys!

thanks for all the advise so far!

as far as ignition. I need to get me a timing gun! because I dont know if it is set correctly right now! problem is, I dont have any marks on my engine too help me set the ignition. probably taken off by previous owner. so I need to get me a timing gun!

I already got rid of all the eco-junk as much as possible. no more air-pumps running on the belts.

tires are up to pressure and checked weekly.

i dont know if the vacuum advance is working. how do I check it?

I dont think I have an electric quadrajet (see picture below).

the cooling fan was attached straigt to the engine. So there was no clutch. Clutch was more expensive to buy and the shop told me everyone buys Flexfans nowadays...but....no mileage improvement, just nice and quiet!

do you have easy guide for tuning a quadrajet?

heres pictures of my carb.

ow...btw I run bi-fuel., I mostly drive LPG and only have regular gas for backup!

http://lh4.ggpht.com/_i4YwYZutwgk/TG...0/P1140385.JPG
http://lh3.ggpht.com/_i4YwYZutwgk/TG...0/P1140386.JPG
http://lh5.ggpht.com/_i4YwYZutwgk/TG...0/P1140387.JPG
http://lh6.ggpht.com/_i4YwYZutwgk/TG...0/P1140390.JPG
http://lh5.ggpht.com/_i4YwYZutwgk/TG...0/P1140392.JPG
http://lh3.ggpht.com/_i4YwYZutwgk/TG...0/P1140393.JPG

Re: Improve mileage 350 with Quadrajet
 

You can check vacuum advance when you get a timing light. After you set your initial timing plug your vacuum can back into a manifold source and you should see the timing increase. You have to disconnect and plug your vacuum advance when you set timing. You've got a vacuum hose behind your carb that has a small screw in it. That would be a good source of manifold vacuum. A manual way to check your vacuum advance. Hook a small vacuum hose to the vacuum pot and suck on it hard. When you release your suction you should hear the vacuum pot snap. Or while sucking feel under the pot and you should feel the connector rod that goes into the distributor move. Ya' I know it sounds goofy but it works.
Doesn't look like a electronic quadrajet. Here's a link with a bunch of quadrajet stuff.
http://www.florida4x4.com/tech/quadrajet/

Re: Improve mileage 350 with Quadrajet
 

To check your vacuum advance, look for the cone shaped metal piece on the side of your distributor, with the small hose coming off of it, its showing in your bottom picture, couple ways to check it is, while the engine is idling, pull the hose, and listen for any change in rpm, or you can pull your distributor cap, and either use a vacuum pump on the hose, mouth..or whatever you choose, and see if its advancing the timing, there is a ring in the lower part of the distributor that the advance mechanism rotates.

Your carb is good, there would have been a electrical plug going into the top of it. It looks like your distributor is good too.

Im not sure of your transmission type, but one other thing you might check, is if it has the electrical lockup turbo 350 transmission in it, it looks like everything else has been switched over, but if you could crawl under it and check if your transmission has a wired plug going to it, the lockup torque converter might not be working anymore. There should either be a plug, or a socket around top of the sealing edge of the transmission pan.

Sounds like you picked the best fan, since the other had no clutch.

I dont happen to have any info on quadrajet tuning, its something I've never got into myself, the metering rods, and pulling the top of the carb off to change it all, just a pain in the butt, and they were replaced with Holleys.

Unless you install a air/fuel ration gauge, you'll have to install a fresh set of plugs, put a few miles on them, and then pull them for a read on the color.

I honestly don't know much about running LPG either.

Hope you get your mileage up, 6 mpg seems pretty bad to me, I'm hoping for better mileage out of my big block once its all wrapped up.

Edit: I just noticed Geezer gave a few good methods to check the advance too.

Re: Improve mileage 350 with Quadrajet
 

All of the above is great advice and I'm not quite sure if your on a budget or not but the cast iron intake and exhaust manifolds really kill the efficiency of any motor look in craigslist and see if you can find some headers tri y headers would probably be best cause they promote low end torque like no tomorrow and torque is what moves yours for the intake have it replaced with an aluminum intake that helps breath and mix the fuel a little better and if possible replace the rotchester carb with a Holley or edelbrock carb also on the pics it looks like your timing is off or such cause it looks like the vacuum canister is way towered the firewall so it's probly off quite a few degrees also make sure that the mechanical advance isn't sticking and replace one of the springs at least with a lighter spring to bring the timing curve in quicker any body see any faultsnin that plan? I don't usually build for gas mileage bit I know that a more efficient engine makes more power with less gas
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Re: Improve mileage 350 with Quadrajet
 

LPG!! Big factor in KPG!! It's a great alternative fuel. However less efficient in power. Extreme cold air hurts. You can probably run without a fan. An electric fan is a great option. Use only as necessary for cooling.

Re: Improve mileage 350 with Quadrajet
 

thanks for all the advise:

Dru: could you point out the cone shaped thing on the distributor for me on the picture? I have no clus what you are referring to?

Re: Improve mileage 350 with Quadrajet
 

Check this out for some Qjet info ;)
http://www.florida4x4.com/tech/quadrajet/

Re: Improve mileage 350 with Quadrajet
 

oke,

i got a problem
I cant find any timing scale or settings on my car. shouldnt this be on the front of the engine?

Re: Improve mileage 350 with Quadrajet
 

If you have a buddy to help you, then you don't technically need any timing marks. Remove the #1 spark plug and find TDC for the compression stroke. Once it's there, make a mark on your harmonic balancer with some sort of paint marker or something that will work on metal. 12 degrees BTDC will be about an inch or so above that mark (as long as you have your timing chain cover with the timing tab). You absolutely sure you don't have a timing mark in your harmonic balancer? Maybe it's just dirty and you can't see anything? Or are you missing the timing tab?

If you're missing your timing tab, you can always time your engine by listening to it. Just remove your vacuum advance, plug it off, and rotate your distributor until your idle goes down, then do the same by rotating the opposite way, and then find the middle of the two. That's *about* 12 degrees.

Also, just out of curiosity, are you certain you have all your plugs wired up the right way? GM v8's will run on 7 or even 6 cylinders (don't ask me how I know that) when the wires are messed up. I'd check your firing order just to be safe.

Re: Improve mileage 350 with Quadrajet
 

should be marks on the dampener
look for a grove in it(put small amount of white paint in the grove ez r 2 c)
maybe have a tab off the timing chain cover with a point


some throttle return springs can be lighter ,easier to push,does the gas pedal moves freely too(but must be able to return)

Re: Improve mileage 350 with Quadrajet
 

the mark isn't very big

Re: Improve mileage 350 with Quadrajet
 

LPG has about 79% of the energy content of gasoline. If you get 8mpg on gas, 6 would be about right on LPG. There is a huge difference between the fuels, "bi fuel" engines are extremely inefficient on LPG. If your engine was tuned exclusively for LPG, at 100+ octane, you would get way, way better mileage.

Re: Improve mileage 350 with Quadrajet
 

well in my non professional opinion to get good fuel economy with a truck don’t drive it... naw the main thing is to keep the back 2 barrels shut as much as possible and don’t let them open up and don’t give it as much gas when you are pulling a hill. I learned this the hard way, I drive 125 miles back and forth from work m-f at first I drove it really bad kicking in the back 2 barrels all the time and doing jack rabbit starts, I would drive to work on 3/4s of a tank, now that I drive like a sane human being I can drive to work and back the same 125 miles on 1/2 a tank just some food for thought

Re: Improve mileage 350 with Quadrajet
 

okay,
made some pictures of the engine! damn its cold outside over here in the NEtherlands. Temperature drop to freezing at night already!

http://lh6.ggpht.com/_i4YwYZutwgk/TN...0/P1160022.JPG
http://lh6.ggpht.com/_i4YwYZutwgk/TN...2/P1160024.JPG
http://lh4.ggpht.com/_i4YwYZutwgk/TN...0/P1160025.JPG
http://lh4.ggpht.com/_i4YwYZutwgk/TN...2/P1160026.JPG
http://lh6.ggpht.com/_i4YwYZutwgk/TN...2/P1160027.JPG
http://lh4.ggpht.com/_i4YwYZutwgk/TN...2/P1160028.JPG

does this help?

Re: Improve mileage 350 with Quadrajet
 

well i don't see the mark on the dampener like in mine.....
no timing mark on my chain cover gona go check another block,should be straight down the middle

these get better mileage when warm ,do you cover the front?we are below 0C already here,and i can't find mine yet

Re: Improve mileage 350 with Quadrajet
 

actually maybe there is

Re: Improve mileage 350 with Quadrajet
 

look for this area

Re: Improve mileage 350 with Quadrajet
 

nope!

checked it again and it isnt there. I'll check again tomorrow. Now it is dark over here!

I do not cover the front during winter. It is our first winter though with this car. We had european cars all before this one.

@big10ratrod77: I know exactly what you mean. but. during this summer we drove 850km at 90-95 km/h (so about 550miles at about 55mph) and we got a MPG of about 6. Then at our destination we drove in very hilly country side, lost of stops lots of different speeds. we got a MPG of 6. Then back in the Netherlands we drive 60/40 highway/city and still we get 6 mpg.

You'd expect there would be more difference between long highway trips and 60/40 home driving. But nothing seems to influence the mileage.

Even changing the sparkplug-wires, coolingfan and cold-air-intake did not change a thing...and all these manufacturers promise big improvements in mileage and power for these parts.....

we even tried driving a whole tank with airco on and then a tank with airco off....nothing seems to influence it.

we drive very relaxed. no rushing. because we are very happy with our ride and hope to keep it for a long time.

thats when I turned to you guys...

help! hahahaha...

I am gonna pull the vacuum advance tomorrow to see if this changes the rpm when idleing..

I dont think the wires are on wrong and I dont think the timing is wrong, because the engine just sounds like a pirring kitten when idleing...or could this still be the case when this stuff is wrong?

Re: Improve mileage 350 with Quadrajet
 

I have a 78 corvette with a 350 and for the life of me could never figure out why it had no power. I took it to a buddy of mine to get it timed, and he figured it out that it was about 120 degrees out of timing with spark plug wires all mixed up and that made it run on only 6 cylinders. And it ran pretty well even like that (I have no idea how or why). It is really easy to time a GM v-8, so don't feel too bad if it does need it.

Re: Improve mileage 350 with Quadrajet
 

The problem in finding your timing tab might be a simple fix lol I think everybody us thinking of the timing tab on the side were as it may be the type. That has the tube in the middle of the timing chain cover look down the back of the water pump and the timing tab should be there
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Re: Improve mileage 350 with Quadrajet
 

Did you crank it over after taking the pictures? The mark line is there somewhere.