6 MPG?!?! Help Me!!

[Low84]

Ok I just did some math, and I'm averaging 6.6 MPG (Its actually probably less) I think I'm running rich. I can smell gas 5ft away from the truck and it has no leaks (atleast visible leaks). I think the timing is off too but I can't do anything about it.

The thing is I'm in college right now, short on cash, and I don't know any local shops. Is the stock Quadrajet just a turn a screw type of affair like the Edelbrock? And which screw is it?

Here is an exploded view of the Quadrajet, to help you (mostly me) explain what I need to do. Somebody help me, I'm not another 25 dollars for a less than 75 mile trip.

http://www.442.com/tech/rochparts.html (It just went down though )

Somebody please help me. PLEASE!!!

[Russell]

Wow, thats some seriously bad mileage! I used to get like 13 with my 3/4 ton, pulling 3000 rpm down the freeway at 65 mph...

Yes, you do adjust your carb's idle mixture by turning the little screws up front on the baseplate, but if you are running rich above an idle, its time for a carb rebuild.

Before you bother with a carb rebuild though, replace the air filter, and fuel filter, plugs, wires, distributer cap, coil, and rotor, and set the timing properly. My guess is that your carb will suddenly be working far better after you get the rest of the ignition system up to snuff, and stop choking it with a plugged up air filter...

It'll cost up front, but doubling your mileage is probally worth the cost!

[68GMC454]

now i know my carb needs rebuilt,,need a new timeing chain i belive,,i only get 6 to 8 mpg in my 3/4 2wd 454 granny tranny, 4:10's..now when i took it to the mountains this summer,,i got 11mpg with a 3000 pound cab over and a load trailer..go figure..but i have never known anybody until i moved out here to utah who got over 6 to 8 with there 454's...i dont get it..

sorry not tryig to steal the thread...but russell is right,,do a major tune up and oil change first,,oil change alone will help out..if it is over do for one..definatly change the air filter...

[84 400]

check that the ckoke is workign right too and not staying slightly closed when driving. good luck

[Low84]

Yeah, I'm kind of regretting having given away my Edelbrock Carb to my brother. But I still have his stock quadrajet, and I think it was running fine, might have to swap them out.

The thing is before I parked the truck. Was sitting for a while. I did a full tune up. Replaced the air filter, new spark plugs, wires, and rotor cap. And parked it a week after that for about 4 months. They should still be good right

And the worst part is the truck is bone stock with the exception of dual flowmasters. Stock 350/350, with stock gearing. This really blows.

Does the timing being off affect gas mileage too, or just throttle response?

[Low84]

Originally Posted by 84 400

check that the ckoke is workign right too and not staying slightly closed when driving. good luck

How do I check that

[Russell]

Timing out will big time throw off your mileage. Was your truck parked indoors or out? If it sat for a while, there is a chance that you may have had condesation form on the inside of the dizzy cap, corroding things up. Its only 4 screws to pop the cap off and take a look

Also, pull a plug and see what it looks like, plugs can tell you a whole lot about how an engine is running.

As mentioned, the choke is another thing to look into, let the engine warm up to full temp, then pop the air cleaner off and make sure that the plate that sits over the primaries is totally vertical, it should be almost entirely closed when the engine is cold starting.

And as far as the carb goes, I'm still of the opinion that a good ol' Q-jet is hard to beat on a relatively stock engine. They take a tune, and hold it very well, and are about as simple as it gets. Rebuilding a carb sounds scary, but once you get it apart, you'll laugh at how simple it really is. Hardest part is setting the float level, and even that is easy as pie!

Oh, speaking of carbs, one more thing to check -- Pop the air cleaner off, and play with the throttle a bit while the engine is off. You want to make sure that both the primaries and secondaries open and close all the way. The secondaries should open at like 3/4 throttle sort of thing, and should snap right shut.

[mySAVIOReigns]

Are you me???

I'm also a college student, and I'm having the same problems.

And you're from TX. Strange.

[Russell]

haha, just be happy you can still drive your old truck at all =/

I'm a University student, and I just got my truck technically street legal as of today, but it won't hit the road until next summer cause there is no way I can afford to drive it

[j hannah]

Do the tuneup,set the timing first. then if its still getting poor mileage, rebuild the carb. If you do tear into the carb, buy a new float,cause you cant always tell if the float is soaking up gas without a float scale. if its too heavy, you cant adjust it properly.

[Low84]

Originally Posted by Russell

Timing out will big time throw off your mileage. Was your truck parked indoors or out? If it sat for a while, there is a chance that you may have had condesation form on the inside of the dizzy cap, corroding things up. Its only 4 screws to pop the cap off and take a look

Also, pull a plug and see what it looks like, plugs can tell you a whole lot about how an engine is running.

As mentioned, the choke is another thing to look into, let the engine warm up to full temp, then pop the air cleaner off and make sure that the plate that sits over the primaries is totally vertical, it should be almost entirely closed when the engine is cold starting.

And as far as the carb goes, I'm still of the opinion that a good ol' Q-jet is hard to beat on a relatively stock engine. They take a tune, and hold it very well, and are about as simple as it gets. Rebuilding a carb sounds scary, but once you get it apart, you'll laugh at how simple it really is. Hardest part is setting the float level, and even that is easy as pie!

Oh, speaking of carbs, one more thing to check -- Pop the air cleaner off, and play with the throttle a bit while the engine is off. You want to make sure that both the primaries and secondaries open and close all the way. The secondaries should open at like 3/4 throttle sort of thing, and should snap right shut.

Alright thanks for the tips/advice. I'll check these things out tomorrow after I'm done with finals Sad thing is the aptment regulations won't let me work on my car inside the complex So I'm going to have to go to a friends house to do all this.

[lilpup69chevy]

you guys need to get smart and let a GOOD carb guy rebuild the q-jet if they aren't all wore out a q jet will be the best for a stock engine, its just too easy these days to slap on a 600 edelbrock and not have to full with it, but i'd just assume have a q jet if its RIGHT and the problem is finding someone who knows how to rebuild and set one like it should be

[Low84]

Originally Posted by mySAVIOReigns

Are you me???

I'm also a college student, and I'm having the same problems.

And you're from TX. Strange.

Wow, thats strange. Must be the Texas air or something throwing the carb tuning off then

[blink32]

I didn't see anywhere you mentioning replacing your fuel lines. If you can smell gas and its just sitting you've got leaks that you can't see. An 84 in the dry texas heat plus rubber lines equals lots of dry-rot. You can spend like $10 on rubber fuel line and replace all of it. I got both my 84 and 76 from California valley. Same relative climate as Texas and both had horrible fuel leaks there were not visible because just about every line was dry-rotted. Replaced them all and the fuel stink went away and my mpg doubled. One of the worst offenders were the fuel filler necks.

[Low84]

Originally Posted by blink32

I didn't see anywhere you mentioning replacing your fuel lines. If you can smell gas and its just sitting you've got leaks that you can't see. An 84 in the dry texas heat plus rubber lines equals lots of dry-rot. You can spend like $10 on rubber fuel line and replace all of it. I got both my 84 and 76 from California valley. Same relative climate as Texas and both had horrible fuel leaks there were not visible because just about every line was dry-rotted. Replaced them all and the fuel stink went away and my mpg doubled. One of the worst offenders were the fuel filler necks.

Yeah, sorry I forgot to mention that. I did replace the fuel lines and the fuel filter. I turned the truck on and gas literally sprayed EVERYWHERE. The lines were old and cracked. So I replaced the lines and filter.

Here is what I've done. The truck had a tune-up done to it about a week before I parked it for 4 or so months. I parked it because it frustrated the living heck out of me, it was leaving me stranded everywhere, I was honestly scared to go pump gas because I was not sure if it would turn back on again (and 90% of the times it didn't ) Anyways I put on a starter, new fuel filter and lines, and a heavy-duty battery (that had been the problem all along the other battery was no good).

Thanks for the advice though. You are right they do get some nasty cracks in them with the type of climate down here.

[Low84]

Originally Posted by j hannah

Do the tuneup,set the timing first. then if its still getting poor mileage, rebuild the carb. If you do tear into the carb, buy a new float,cause you cant always tell if the float is soaking up gas without a float scale. if its too heavy, you cant adjust it properly.

Will do. What is a normal MPG for a stock 350/350?

[blink32]

If you did all that then i'm on board with everyone else I guess. Carb problem + timing maybe. When it leaves you stranded what are the symptoms?

[jkaylor68gmc]

Do not rebuild a Quadrajunk. You will be much better off purchasing an entry level carb such as a Edelbrock 500 or Holley 650 for around 200 bucks.

[1969K10]

Originally Posted by Low84

Will do. What is a normal MPG for a stock 350/350?

Has more to do with your rear gears than motor/tranny combo. i've got a Q-jet from a 79 camaro in my truck. it's a great carb, and holds tuning well. however, once it starts to go, it goes quickly. i'm in a similar situation. it was running OK until I had it off to work on something else... I know mine needs a rebuild..

Good luck!

[Low84]

Originally Posted by blink32

If you did all that then i'm on board with everyone else I guess. Carb problem + timing maybe. When it leaves you stranded what are the symptoms?

It no longer does. But when it did it was a a weak cranking on the first try, on the second try it would make a loud pop coming from the starter area, that or the good old CLICK and nothing after that, no lights, stereo, NOTHING completley dead. I found out when I took my first battery in for a replacement they gave me the lowest of the low in terms of battery and since I have a little audio system going on in it, the battery was not up to the task.

However, I was driving the truck the whole day and everything was perfect (with the exception of poor gas mileage, and poor throttle response) Right before leaving home I turned the truck on and put it in reverse to pull out of the driveway and the truck started to get real weak and turned off on me. Took me two minutes to turn it back on, but it hasn't done it again???

Originally Posted by 1969K10

Has more to do with your rear gears than motor/tranny combo. i've got a Q-jet from a 79 camaro in my truck. it's a great carb, and holds tuning well. however, once it starts to go, it goes quickly. i'm in a similar situation. it was running OK until I had it off to work on something else... I know mine needs a rebuild..

Good luck!

Thanks. Its stock gearing too. I wanted to get a stall and 3.73 gears later on, but the way things are right now.........I don't think I'm going to have enough money to buy pretty much anything. I spent close to $600 dolllars just to get it somewhat road-worthy in two days, and its still no-where near to where I wanted it to be performing

On the bright side, it looks like my friend just found a free truck for me, so that kind of cheers me up.

[piecesparts]

Going for that Engineering degree? The items on the exploded view of the carb that are marked (Idle adjust) #41, are the idle adjustment screws. Those are only the basics and really do not affect your gas mileage that much. Now for another question----Is the carb a Rochester made quadrajet or is it a Carter brand quad? The reason that I ask, is that the Rochester is the better of the two. The Rochester has brass bushings in the different areas that the carter doesn't. I agree that the carb needs a rebuild and that you are defintily running on the rich side of being poor.

Also, you seriously need to look at your timing on that motor. I would find a timing light or get someone that has one to check it out. If you are timed wrong, then everything that you do to the carb is wasted.

[Low84]

Originally Posted by piecesparts

Going for that Engineering degree? The items on the exploded view of the carb that are marked (Idle adjust) #41, are the idle adjustment screws. Those are only the basics and really do not affect your gas mileage that much. Now for another question----Is the carb a Rochester made quadrajet or is it a Carter brand quad? The reason that I ask, is that the Rochester is the better of the two. The Rochester has brass bushings in the different areas that the carter doesn't. I agree that the carb needs a rebuild and that you are defintily running on the rich side of being poor.

Also, you seriously need to look at your timing on that motor. I would find a timing light or get someone that has one to check it out. If you are timed wrong, then everything that you do to the carb is wasted.

LOL. Nah, ultimately I want to get a Physical Therapy degree. I'm not too sure on the make of the carb but I think it is a Rochester.

And thanks for the info.

[piecesparts]

Even a physical Therapist can fix a broken truck.... I would do the timing first, to get the motor running where it should, then look at the carb. Remember, if you do decide to change the carb to an Edelbrock 1406 design, You will have to either change the intake manifold to bolt somethng like a square bore carb on, or get an adapter to allow for the square bore to bolt to the spread bore intake design. That is what makes that a different deal.

[Low84]

Well, I went to a friends house and his dad knows a bit of cars. We/he tried to tune the carb and that thing is GONE. The screws weren't doing a thing, NOTHING. The truck wouldn't even stumble much less die off. I think its safe to say I need a new carb The timing was also way off, he moved it down a bit and the thing was idling very weird. Sounded too low. Then I noticed he had put it to I believe 4 degrees, because thats what the sticker said. The problem is the sticker is for a 305 Does anybody know what the timing should be at for a 350?


By the way I accompanied my friend to the track and decided to run the truck while I was there. 18.8

I was running 89 octane at the track, and on the way back I switched back to 87 octane and the thing feels a lot stronger. I think maybe a 18.5.

Is it possible that lower octane can have that effect? Or am I trying to make myself feel better?

[Low84]

Oh I forgot to mention. I now have a HUGE exhaust leak