Yep. I calculated it. There's something wrong here, big time. Now, this is city driving. I drive back and forth from my place to my fiancee's. That's all. It's about a fifteen mile trip, each eay. I think. Anyhow, something's got to change.

I rebuilt the carb a while back, and that didnt make a difference. It's got 43 rods and 73 jets, and whatever secondary rods came stock on the l69 cars, I forget. Nothing too rich, anyway. Other than that, just an open element, no cat, 1.6 rockers and better valve springs, and that's it for engine mods. I run it at about 180 degrees farenheight, but I have recently started running it at 220 to see if there's a difference, which there doesnt seem to be.

What the heck can I do? It's costing me 200 bucks a month for gas where I live. I gotta do something. Any ideas?

It also isnt shooting any black smoke out or anything. Doesnt seem like it's idling rich, either. So I dont have the faintest clue what the heck it is.

 

Perhaps you need a locking gas cap.

 

Tell your girlfriend she needs to get a bus pass or it's over.

 

fuel leak?

 

As stated though, check your gas cap seal and see if you're leaking fuel anywhere. Check O2 sensor and all the usual tuneup stuff (ignition, air filter, etc.). Small things add up.

Did this just start happening after something changed, or has it been happening for a long time? What changed/happened right before this gas mileage problem?

 

is it a consistant 60mpg? if it is then you might have a fuel leak,try turning the car on but not starting it and check for leaks. also try parking your car on a hill in diffrent directions,gas may slosh out of a hole when driving.so check that as well.

are you babying the throttle? or peeling tires at every light?


also,check a your tire pressure,and get a locking gas cap just in case.

or swap out that gas hog for a duke ,or v6 .

v8s are fun,but expensive when gas is $3 a gallon.

 

brake drag, bad wheel bearings, put your hand near your wheels after driving check for excessive heat. How is your trans? Does it go into lockup at highway speeds? To check drive about 60MPH and lightly touch the brakes it should go out of lockup and your RPMs will go up about 500.

 

Haha she has a bus pass. And it sure as hll helps, but still. Ok:

-I have a locking gas cap. And I can watch it steadily go down. I have checked arond for a fuel leak, but not as extensively as I should have. I'l go give it another pass.

-I have done all the regular tuneup things lately and it didn't just start happening. It's always been like that. Perhaps something a previous owner did to an emisions component?

-The wiring to the TCC sems a little butchered, I'm not actualy sure if it is locking. When I am cruising and tap the brakes the RPMS do not go up. In fact, they will flash up about 500 RPMs when I hit the GAS...

-I am driving it pretty nicely. A few 4000 RPM shifts, but certainly not peeling at every light

-the fuel mileage is constant, yes

-tire pressure is ok

Maybe I should swap for a duke. lol. Well I will go check for heat around teh wheels next time I drive it (do I recal teh wheel alignment guy telling me I should watch the front bearings?) and I wil have a good lok for leaks again.

Thanks guys!

-I dont know about brake drag. It doesnt pull or anything like that, and last time I checked my pads/shoes they were all fine

 

If you had a bearing or brake dragging, you'd have a noticeable lack of acceleration. Your TCC shouldn't be locking up much anyway in city driving. I suppose another thing to check is that the fuel level shown on the gauge is actually correct.

 

Yeah. When I hit the brakes the needle goes down a fair bit. Likewise when I accelerate. So I basically assume the level is more or less correct while I am in motion on a level surface, or have been stopped for a fairly long time.

Well I do have crappy acceleration, but I think that's due to being an LG4 buttoned to an automatic in a 3400 pound car.

 

and even with a non-locking torque convertor I doubt he is going to get 60miles per tank.
with my old camaro running 4.11 rear end and a TH350 I was still getting better mileage then that.

an o2 sensor might make a difference but by itself I doubt that much of a difference.
I don't know if the carbed cars had a computer to run codes on but if nothing else you can maybe try running a volt meter to it. I ended up trying that on my mazda once when I didn't feel like taking the whole interior apart to get to the ECU. just ran a clip to the o2 wire and ran it under the door into the cab and then up to the multimeter and checked for voltage.
should swing around the .3-.6 range if I remember right, but should avg around the .4-5 range again if I remember right.
if it stays up to like .7-9 or so something isn't right either with the o2 or the way the car is burning the fuel or you just have too much fuel.


even if the exhuast isn't churning out smoke how does the exhuast smell at idle. if it's ok maybe your idle circuit is fine but your primary circuit is running way rich. read the o2 above. it's not as accurate as a wideband but will still give you some idea this way you can check at idle and cruise.

also while on that part any hesitations, bogs, stumbles, jerkyness while moving from very light load like you know in gear not holding the brake to maybe 1/4-1/2 throttle? try pushing the pedal at different speeds when doing this. might indicate a tuning issue with the carb where the primary and the idle circuit might not be very well mated with one another.

how do the plugs look

any miss in the way it runs?

might want to do a resistance reading on your plug wires also.

also check your timing.


if you can also check the parking brake. move fairly slow and easily lift on the parking brake if you feel it grab the moment you start lifting on the parking brake it might be dragging all the time and need adjustment.

whats the fuel pressure at by chance if you have the ability to check it out preferably at the carb itself. if your only running something like 2 psi at the carb when it should be 6 chances are it's not a faulty pump but rather a leak in the lines somewhere bleeding off pressure and precious gas.

maybe you have a wheel bearing that's shot to shiz. try pushing and pulling on the top of the wheel to see if there is a lot of play or maybe even jack the wheels up one by one and try this or maybe rotate the tires as well and see if one just doesn't want to move. generally though I would say you would have an idea on this being that it would prolly make some noise and/or be a little iffy when driving with a uncertain on center feel.

how does the car accelerate at WOT or partial throttle?? fast, slow, unsteady?

sorry about all the questions I'm just trying to give you some ideas to work with. and true each one of these by themself I don't think would cause it to be this bad and I prolly gave you more ideas then you need but hey it's always a good time to check other things out as well right?

 

No computer in his car.

 

Hey, I dont mind the questions at a. Well, as Apeiron said, I have no computer at all. No o2 sensor, either. I cant check the fuel pressure, but I just replaced the pump a couple of months ago. the exhaust smells fine at idle. That's waht really confuses me. The plugs looked perfect last time I checked. I should check the wires, though. Thank *** I brought the multimeter with me to college. The engine also runs fine. Nice and smooth acceleration, too. I had a hard time tuning the ff-idle bog out of it when I rebuilt the carb, but that's all taken care of now. I want to go to the local junkyard and se if I can find some leaner secondary rods (probably CH, as they are stock) and see what happens.

The engine just doesnt seem like it is losing any power, though. I'm so confused, and this is eating my budget.

 

With my 350/th350/4.11 setup im lucky to get 50km in town driving on a full tank which really sux. Even if im easy on the gas and only drive to work (3km) and back with minimal messing around i can barely go a week on a tank.


But i dont see how your setup could hog this much fuel.


Although i did just find out my tranny might be a th350c, so if it is and i rig up the lockup to a toggle switch i should be getting a bit better mileage.

 

You'll have something going on. A fuel system leak perhaps? Maybe a bad pump spewing fuel out? Choke functioning properly? How is your timing? Centrifical and Vacuum advance mechanisms working? Valve adjustment right? What about you cam/crank correlation?

I have a 5,300 lbs brick with a 340 FWHP 305 TBI, 700r4 w/ 2,000 rpm stall, and 3.73 gears, sits at idle with the A/C on at several long lights daily, I occassionally beat on it, and still gets over 15 mpg. Your fuel consumption doesn't make sense!!!

 

Yeah I'll say it doesnt make sense. Well I know the timing is ok. I set it myself a while back. 4 degrees past stock, which put me at 26 total, I think. Also, when I unplug the vacuum line to the dizzy the engine idles a lot worse. so.

Same with the valves, I adjusted them not long ago..


Well I just drove back from my fiancee's place, and I checked the wheels for radiating heat. Nothing. I also got up to 100 kph and tapped the brakes, and the rpms did not flash up, so I dont think the tcc is locking. I dont think it ever did, as a matter of fact. I'm thinking it's a combination of things here.. tcc not locking, perhaps emissions, and maybe my choke..

I have my choke set to be fully off just at about 180 degrees, which is what I normally run the engine at. This makes it a bit hard to cold start, but I dont mind. Otherwise the choke would always be on. I have started letting the engine run up to normal 220* operating temperature (by toggling my manual fan switch off) and I have noticed an improvement.

Strange.

 

60 "miles" to a tank? did i read that right?
that comes out to like what ~4mpg on our cars??

is that even possible on a 305 without blowing out enormous clouds of smoke or leaving a noticable trail of gas behind?!

are you sure someones not stealing your gas?? last locking gas cap that gave me a problem i opened with a screw driver, it didnt break it either, heh

 

isn't there some sort of comptuer controlling the carb?

 

This may well be the dumbest question in the thread so far, but have you checked the gas tank for any large dents etc. which would significantly reduce the volume and hence the amount of gas available, althoug I assume you've checked the amount of gas you're putting in the tank against the miles travelled when you fill up..

 

Rx7: Nope. Many American Carbureted fbods had a computer controlling the carb, but not mine. Any spreadbore qjet I find from a junkyard, even from the early seventies, will bolt right up.

I havent looked for any dents in the tank.. The never occurred to me. But those would have to be HUGE dents, right?

When I fill up, I put $30.00 worth of gas in. That equates to a little more than 25 litres, most of the time. That is usually good for 3 round trips to my fiancee's place, which means it's costing ten bucks in gas to go like 20 km!

 

I'm at work so I didn't read the entire thread, but your not running split fire plugs are you?

The sudden change in temp sounds alot like my car when I swapped over to the $5.00 plug.


anyway just wondering

 

25 litres is about 6.6 US wet gallons, which is less than half a tank. 3 round trips of 15 miles each way is 90 miles. You're getting about 13.6 mpg by those numbers. Not great, but not completely terrible by Vancouver traffic standards.

 

25 litres per fill up = 6.58 us gallons/ 60 miles = 9.13 mpg

Not good. I would take a serious look at your carb.

 

yeah, 9-13ish sounds about right, now that the engine is running hotter... but i cant believe the operating temperature would make that kind of difference. there must be something else related...

and no, i am not using spitfire plugs.

 

no, it's less. I mean I got 60 miles when i filled the tank right up.

I also think I might be wrong on the distance of 1 round trip. have to check on that..

 

From BCIT to where?

 

wow i'm late on this one....

first of all, fiancee??? holy cow, good job buddy! (aren't you like 18??? good ***...)

this happened all the time, or since we monkeyed with it?

you have DR secondary rods (those ones that I gave you?), and K hanger I think.


Just FYI to everyone else:
We adjusted his primary power piston such that he had no bog. Perhaps I was overzealous? Then again, you'd be puffing black as you drove.

13MPG in city sounds normal for a carbed V-8. I could get 200kms on tank on the highway (no OD), and I never checked city, as it was dismal.

I have a tiny tank too, I could only squeeze in $30 of gas maybe.... Is gas still like $.94/l there? if not, haha!

I'll have to show you what i'm doing with my car now, it's a shell in the garage

 

There probably wouldn't be black smoke unless it was way rich. Driving around all the time at 13:1 all the time would tend to eat up gas in a hurry though.

 

The far point of UBC. >.<




Thanks Jay! Yeah, I'm eighteen. I know, it's strange.

Anyhow, it was always pretty bad. I think it actually got better after you had helped me out with it, though I have never really tracked my mileage until now. Too afraid to.

Right, DR rods. Those were the ones. And gas here is $1.06-$1.18 depending on the phases of the moon.

A shell in the garage, eh? Nice! I wanna see!


Again, about the smoke, that's the thing that gets me. It doesnt smell rich at idle, and it doesnt smoke when I rev it.. I still have to check again for fuel leaks. When I changed the pump I replaced one of the rubber hoses because it was questionable, so I will start there, and then work back to the tank, I guess. Maybe play with the choke a bit, too.

But I still don't get how changing the operating temperature made as much of a difference as it did..

 

It's about 12 miles from BCIT to UBC on Grandview Highway. Depending on the time of day it can be an hour of travel time each way of course.

 

fuel burns more completely and "better" at the correct operating temp. I'll upload a link to some recent pics of my car. Interior is "done", stereo is in the works. Then on to rear suspension, front, then finally motor/driveline, and bodywork..

Might as well change your fuel filter, since it's only $2, if it's been a while.

if you're getting crappy mileage while driving around normally (normally = granny style), then maybe your primaries are too rich.
You could go to a smaller jet size, and see if you don't get a drop in power. if you don't lose power, then you should be fine.
73 jets, 43 rods right? That's what I have, same with you? You could try a 72 or 71 or something. Any time to scrounge junkyards? at least you don't get cold weather there (bastard), so you can go whenever, that is if you don't have much homework


I'll give a link when I get home here.

 

oh yea, forgot, been to Port Kells yet?
See if you run into a guy with a red '90 Supercoupe. He'll give you a run for your money.... (or just blow your doors off like nobodys business)

 

Well I thought it was better to let the engine run lower, if possible..? My tranny runs at like 200 with the fan off, 180 with it on..

Anyhow, yeah, 43 rods and 73 jets. I have been meaning to go to a junkyard for a while, but haven't had time yet. I'll try to go this weekend if it isnt raining cats and dogs again. (what was that about weather? )

Maybe I should change the rods, though. That way I shouldnt lose power, right?


Also, er, port kells? Never heard of it. I have been meaning to go check out the races for a while, but I figured they wouldnt be running at this time of year..

 

port kells is where people meet up to street race. it's like fast and the furious there (referring to quantity of people), except with actually fast cars there. muscle cars, hot rods, japanese imports. The ricers just watch. Go check it out, and just watch for a bit. It's like a car show, except people drive off together... Cops galore. Maybe Apeiron knows more about this place, i've only been there once...

rods are not effecting it if you go full throttle so..... yes, yes, sorry, you could try fatter rods... I really thought that one through too... huh...
that way if you go WOT, the rod/jet ratio is the same, once you're on the power tip. yet your cruise is more lean.

 

Port Kells is an industrial park in Surrey. You could go there, or you could go to Mission and see cars that actually are fast.

 

Mission? I think I remember driving through there.... At the same point I was getting mad at the road leading into Vancouver for being so freaking long!

Alright. I will go see if I can find some fatter rods. Hope I dont have to buy a new air horn gasket..

EDIT: Think fatter rods might also bring that awful bog back?

 

Mission is where the racetrack is. You would have driven past it, not through it. It's on the other side of the river.

Instead of just throwing different tunings at the problem, you could try to figure out if you're actually running rich first. Even if you had to spend $100 on dyno time or something you'd make that money back pretty quick. If nothing else, take it in for an AirCare inspection and see what your HC and CO emissions are like.

For that matter, it doesn't sound like you've actually established what your mileage really is with any accuracy yet.

 

Carb setup for mileage and HP on a nearly stock 305. Take your ordinary run of the mill Q-Jet. Rebuild it to specs as far as all the adjustments go. The primary jet needs to be a 72 or 73. Go 50M on the primary rod. Chevy Trucks, Vans, SUVs have a power piston spring that is fully extended at about 8" HG of vacuum(helps eliminate the bog without killing mileage too much as trucks pulling things are heavy and need the power help). You need to adjust the APT screw under the just in front of the power piston to 2 turns out. Screw the screw in and back it out 2 turns. A little less is leaner and a little farther out is richer. Use the screw to adjust the lean part throttle bog rather than changing the metering rods. Use a DR rod on a F hanger. You can get the DR rods from a L69 or a LE9 truck/van engine. You can find the F hanger on most 307 oldsmobiles. Then adjust the secondary air valve to 7/8 or 1 turn from 0 tension. That kicks the secondaries in pretty late, but eliminates the typical Q-Jet stumble when you romp on it. Make sure that your throttle plates/ idle speed screw is opened as little as possible. Use your idle mixture screws to get the mixture right. I typically back the idle speed screw all the way out and then turn it in 2 turns after it makes contact with the linkage for a baseline. I then turn the mixture screws in until they are LIGHTLY seated, then turn them out 2 1/2 times. That typically gets the engine to idle pretty good assuming no vacuum leaks, etc.

 

mission is a city, just making sure everyone knows that.

port kells is an area right? or can refer to an area ? I think there was 4 autoparts stores in one area, lordco....some others... Those parking lots are the meeting areas on friday/saturday nights.

the bog was because the absolute fattest part of the rod was in the jet, not sure it's size, but it's huge. As long as you don't get a rod that big, then it shouldn't come back. If you go to giant rods, yes, it will creep back, not a bog, but just no power... So go in small steps maybe. I think I have some 44 rods, and 45's maybe... I know I have 50's. Fast355 runs some giant fat rod (50M? )and he's doing ok, so maybe it's not so bad.

wait, I think that's in reference to cc-qjet and therefore is totally different.

 

The carbs I build for mild near stock 305s and 350s as well as the 307, 350, 403 olds, and 301 pontiac run 50M rods. They are pretty fat rods compared to most. It is really a balancing act with them. The APT screw provides this balancing act. Sounds as if when under light load you have the mixture about right, but as the load gets heavier you are getting overich and losing power. You should have no problem reaching say 3,500-4,000 rpm on the primaries, very crisp and smoothly. You changed up all the balance to get rid of a little part throttle bog which is a bad thing. Assuming you have the APT screw you can just move the fatter rod up in the jet a little and get more fuel.

 

Wait a minute though, are you getting 60 miles per tank, or 60 miles per 25 litres? If it's 60 miles per 25 litres, then you'd be getting more than 120 miles, or roughly 200kms per tank (I'm assuming a thirdgen tank is at least 50 litres...I'm not entirely certain what it is). That's not as horrifically unreasonable for an underpowered, heavy V8 car in town driving.

 

That's exactly what I'm saying too.

 

Since when is the LG4 underpowered for around town driving? I guess different people have different expectations, but with peak torque at 2,000 rpm, I find the stock cam 305s to be great around town drivers. You just don't have to rev them much and the torque just pulls you. I would rather have a 305 and lug it around while driving around town than have a 4.8 or 5.3 and have to rev it to get moving. My moms has a suburban like that and it SUCKS gas around town.

 

25 Liters is 6.604 US gallons.
60 miles/ 6.6 gallons = 9.09 MPG
Still unreasonable IMHO.

IIRC, 16 gallons is a typical F-body tank, that give a range of 145 miles. Not good at all for a stock engine or one that is almost stock.

 

fast, just double checking here, you're talking about a cc-qjet? Where the rods have the springs on them, and the number (50M) has no meaning for it's size?
or are we talking about a non-cc q-jet? I just want to make sure we're on the same page.


Ryan, the APT screw he's talking about (just making sure you're following), is that flat blade screwdriver looking thing right in front of the power piston, that controlled how far down your primary rods are sucked down at high vacuum (low RPM). When I got to it, it was set too low (screw tightened) such that the rod was very low, and "plugged" the jet. This was bad/wrong. We didn't change the balance, but fixed a problem.
However, a fatter rod and some fiddling with that screw might solve the "problem".

I agree though, might as well check your mileage again. Fill the tank to the gunnels, then run it low and refill and check your mileage. 13mpg in town, 20mpg on highway is normal for my non-od car.

 

I am talking about non-computer Q-Jet. Most of my dealings are in non computer controlled older cars and trucks. The CCC Q-Jet are a rare find around here as most have gone to an old school distributer and non C3 carb. 50M is the number that is stamped into the rod and has to deal with the biggest size in thousandths of an inch of the rod (the main body is .050" diameter). You can still get them from summit or Jegs for about $8.00 a pair last time I checked.

My APT screw as well as some others that I have run across, didn't have a flat blade to it. Mine was some form of tamperproof deal. I had to get on it with a pair of needle nose to turn it as I could not find a thing to turn it. I have seen many other that are a flat bladed type.

Typically your off-idle part throttle bog will re-appear on the highway during steady state cruise as a lean surge.

 

Nono, guys. I meant I got 60 miles out of a FULL tank, not just 25 litres.

But that was before I started messing around with the carb and the engine temperature and so forth. Now it probably IS more like 60 miles per 25 litres.. I have to make a few more trips over there and find out for sure.


I'm following. I remember what it was that you turned, but as Fast355 said, I dont recall it having a flat blade on it. I thought it had some sort of hexagonal thing sticking up out of it? Well whatever it looked like, I know what you're talking about. The thing that limits how far down the power piston goes. I think that is in fact set correctly, though. Maybe what I'll do is throw some bigger rods in there and see what happens, then work from there.

I also need to figure out why my torque converter isnt locking..



Also, holy crap, guys, I REALLY appreciate all the help you are giving me.

 

oh I get it, you went to a 220F t-stat eh? that shouldn't really change much...

yea, that adjustment has what looks like a flatblade to the top of it. A fat flate blade (not wide, but fat...) . So you have to grab it with needle nose pliers IIRC.

hmm, no clue on the lockup, that's a q for the tranny board... or just not me... But that'll hurt you mileage a bit....

I don't take a lot of pictures, unless I need help with something, but I have 3, me after I finally (proudly) got the rear axle out, all by my lonesome, and what i'm working on now, the stereo stuff. Then i'll be done the interior completely, and I can get an axle girdle and put the rear back in (with new bearings probably...)
oh, and the axle is the 3rd pic.

new pics

 

Take a burn out the valley and check out the highway mileage.

 

EXACTLY. Few people do PURE city driving and it can be brutal when you finally do. If all you are doing is city driving in stop/go traffic, your engine is probably carboned up which will affect mileage. Also, do you have a cat on the car? If so, it is probably an older type and has never been replaced.

If it makes you feel good, I have an old 1980 Granada with a 250-6 cyl for a winter beater car. In PURE city driving, it doesn't even get 10 mpg. On the highway it MIGHT get up to 18 mpg. This is after I removed the cat. Before that, it was even worst. This car is just a pig on gas. No wonder most of these cars were crushed.