i'm sure you have all heard this situation before but I got ****ty gas mileage really bad.... just hear me out on this though... k..

k, i got 91, 305, tbi, was all stock... 130,000 miles,, and well i have been driving a combo of highway and city miles... i mean i live in a town of 7000 so its not like rush hour traffic and well i was trying really hard to get good gas mileage bein nice on the gas and all and i was gettin average 8 - 12 MPG.... thats horrible... i mean trucks get better then that... so i put new plugs wires,, and a few other tune up thingys and stayed the same... somethin isn't right can't be....

wrost part is i just put new intake carb and all that **** and carbs... are suppose to get wrost then tbi... what the hell am i gunna do... does anyone have this ****ty of mileage... ??



Vetter

 

yup, mine sucks gas like it's a frat guy doin a beer bong. i've got a cam and a 3spd trans and a 3.42 rear, no emmissions, weiand stealth and a demon carb...a lil bigger than your edelbrock, and i get in the 6-8 range....i can get about 110 miles on a full tank...no idea why it's so poor, the engine really isn't that radical

 

ya i got a 4 spd auto tranny 700r4.... with stock rear end like 2.73 or whatever it is i don't even know but the car just won't do it... with fuel injection even i was gettin that poor now i got my 600cfm carb on there instead which was pry a mistake in the mpg idea but i havn't tested this setup yet but i'm scared to see how bad it will be now.... ***... are some cars just this poor or whats the deal... i mean i try so hard for good mileage keep rpms under 2500 as best as i can and it does that.... GOSH>>> NOW WHAT

 

even if the check engine light isnt on.. see if you can pull any codes.


i had that prob with my LO3..... after replacing the MAP it got alittle better, and after replacing the EGR it became great....



i would see if you get any codes..... im guessing you might have a hidden code 32... if thats the case, replace your EGR valve (check the hoses first of course)....

 

you probly need to tune your carb and check what your timing is...

a overdrive trans would help you alot too...

for a manual id go with a T56 of course... for a auto.... well i dont like autos

but a used 700R4 can usually be found for $100

 

wait... nathan2003, you have a carb on there now?

lol.. ahh.

what are you using for ignition, and are you running rich? whats your timing?

 

see when i had the tbi on there the timing was good... and i have OverDrive so thats not a problem i mean I would be running 65, 70 down the highway with my tbi and i'd be running 2,200 rpm or so... i mean it was a very reasonable rpm... and yet it was that bad... see the weird part of it was like a year prior i had watched my mpg and i was gettin like 18 - 25mpg and over this last summer realized i was fillin up more so i checked it and thats when i realized what is going on now...

see i know whit this new carb on i should be expectin wrost mpg but i havn't driven it really with my new carb... like i havn't had a chance to check the mpg with it yet... i'm just talkin about before what was so wrong... cause i know it will carry over into my carb now...


what do you mean by what am i running for an ingnition... is there somethin that i could change that would make that differeance or... i don't really understand what you mean by what are you running for an ignition... ??


but ya i'm going to bed now so post post and post some more away with ideas thoughts suggestions and i'll be on here tomorrow as soon as i can to see what you all came up with and to give a little more info if needed... thx guys...




Vetter

 

yea, my carb does need to be tuned...
i can't keep an overdrive trans together, i blew up three and bought a 3spd, i love it...gotta save up for a gear vendors unit though

 

i mean, since you took out your TBI and put a carb on, are you still running the computer controled distrib, or are you using a big, standalone HEI?


and check your MPG now that you have a carb on it.. dont just assume the problem "transfered" over.. your prob sounded like classic bad EGR...... EGR goes bad on the car and you get ****ty miliage.. you fix it, and you get better MPG


but since you ditched that entire engine setup, i suggest you find if you still have that prob first.

 

for the price of a gear vendors, you could have a overdrive tranny built that would hold the power.

plus you wouldnt have to change your driveshaft length.

plus you wouldnt have a unusual setup then...

 

ya i got all the proper things switched that need to be switched for when i did the tbi to carb change over.... hei distrib... regulator and countless little things here and there... i'll tell you all that was a bigger project then i thought itd be.... but ya i havn't done an actual test to see what my mpg is but i had to fill up 2 times in one weekbut things werern't all set right too i understand that point... right now my cars at the shop getting a new steering column and gettin the timing set and fuel pressure set and there going to toy with my carb so as soon as i get it back i'll see what kinda MPG i have in order for me to know for sure wether or not the problem transferred... i'll keep ya all posted up on this...

later


Vetter

 

anyone else have this problem with mileage.. i have seen some posts on here from others askin what everyone has for gas mileage.. and some of you with your 350's and decked out gas hogs are gettin three times better then me... like on average on the posts that i've seen everyone gets 17-27 or so... i would die for that... what isn't working right thats causing this low average of mine 7-12mpg.... would like any ideas or advice thx...



Vetter

 

Ok, this is the last time i'm going to post my own thread in order for it to get bumped up to the top.... the reason i posted here on thirdgen forums is because your all camaro freaks and youve all expierianced the oddest things with your f-bods.... thats why i came here and posted was for answers suggestions... help... wantin to know if i'm the only one out here expieriancing this problem or if alot of you have it... come on now... i'm just a simple person looking for some answers....


is it just my ****ty luck that i got a **** **** poor motor that won't get a good MPG average... come on now thirdgen... you all have questions all of us do but for everyquestion everyone here asks they need to do there fair share on answering questions too... even if it does seem like a stupid question to you share your input... please help me out... i wanna ask the pros *thirdgen* before i take it to some car shop and spend boku bucks on tryin to figure out what the problem is and then fixin it and so forth... help me out here... if i dont' get any replies after this i'll just forget it and live with it but i'd really like some help thx... later..



Vetter

 

heres the problem.

you changed your car. alot. you dont have the same fuel injection that gave you the bad miliage. you now have a carb and a stand alone HEI.


you havent driven the car that much since then, and you dont even know if the MPG problem still exists.


heres what you need to do:

when you get your car back, drive it and keep track of your MPG... if the car drives fine, and the MPG is good, then you're set.

otherwise, post in the carb board about your prob... if you need to tweak the carb, you can tell them your exact symptoms and they will try to help you find a list of solutions..





saying "my car had this problem and i changed all this stuff what can i do about this problem" over and over again isnt going to get anymore replys. people look in here, see what you said, realize they cant help from any info you gave, and leave.

just chill, get your car back from teh shop.. you said the shop was "toying" with the carb and fuel pressure... perhaps you should just wait until they finish setting it up and see where you're at.

 

I'd like to apologize for that post I made... it was out of line and rude. Mr. Dude your right that crying isn't going to help at all, its just that it has been a very frustrating day and I was sick of all the hear say and so forth and I wanted answers even if I had to demand them. So I'd like to give a big apology to all the members of thirdgen that read my post. I'm really sorry for blowing up like that.

I know what you mean Mr. Dude about wait till I get my car back and actually do a good test to see what I have for MPG now, but I was also very curious as to why my fuel injected setup was putting out such horrible mileage. Ecspecially since the previous summer I was getting 22-27 MPG, and now this summer I have a wopping 8-12 MPG. I am also going to go post this in the TBI forum and see what they say, but wanted to ask here because this forum seems to be more active.

Again I would like to apologize for my attitude, I was totally outta line when I wrote that and hope you all understand that, I mean we've all been to that point of frustration at some time and just are really short tempered. Thanks for you time and help.




Later,
Vetter

 

Your carb should be able to match the TBI for mileage and simply blow it away for hp

It'll work out just fine. We've all been through the bad mileage blues and you DO come out the other end

 

first tank of gas ran through with my carburetor setup and mileage was 11.5 MPG. This is about what my car was getting before. Does that sound reasonable for a carburetor or what ? i'm surprised it was the same as fuel injectedc... i just wish it coluld go 20 or even 16 mpg...



nathan vetter

 

You should be getting a little less then with the TBI. Less because you dont have an ECM leaning the mixture constantly.
Make sure the timing is correct, mention of a shop doing it so you may have it set correctly by them. A calibration kit should be used also. If its a 1406 then you have a fairly rich off idle setup for a 305. I suggest using the book the carb came with and leaning the mixture. Buy a calibration kit for the smaller 500cfm carb, it will come with the proper jets 92- to lean it out. I would try 92 primary and 92 secondary jets with the orange springs and the proper rods. I left my book at work so I dont have the rod numbers right now, I think its choice #11 for the calibration. It worked very well for my old 305, driven very easy it did quite well for a non mantained 80K engine and once the 3.42's were in it spanked all the other cars I raced on the street.

 

My 350 in my sig is actually doing pretty well on milage. I have been getting about 5 days to a full tank now. I do alot of driving.

Make sure the carb is tuned in. That makes a HUGE difference. Also check for slow leaks. I had a clear site plug leaking which caused terrible milage.

I still have 2.73s and a 700r4...I may be getting a TCI th350 and some 3.73s soon. Bye Bye milage.

BTW I averaged 19mpg on the interstate to thirdgen nationals BUT the car was VERY BADLY out of tune. Running extremely rich, distributor wasn't tight enough and it jumped time BAD, and in the rush to get things ready I accidently switch #5 and #7 plug wires........I also fought a dieseling problem since the new engine install...do believe it was a leaky intake gasket.

Installed the new cam and the dieseling stopped completely and MPG shot way way up.

 

wow.. big progress made today, i had 15 MPG ! ! wow, but like all of that was highway to not to much room to brag i suppose. i have turned the fuel pressure like way way down and the idle mixture screws down and the carb is still running very rich, it puffs out black smoke and has lots of carbon build up happening. so, SSC, i live in western iowa and my 305 is stock but no emissions , flowmaster exhuast and this new intake and carb, thats all it has for modifications, what should i change my rods and all that little stuff you were talkin too ?? i looked in my book and am not sure how far i wanna go... if i remember right i was thinkin stage 7 or whatever you wanna call it but, if you could get back to me on which one you used and if anyone could just give me a brief definition on how to install new rods, springs, because words of wisdom from all of you are usually a bit easier to understand then words from a manual thx alot, keep ya informed of progress..




nathan vetter

 

Wow that's terrible mileage.

I used to get that with my 455 pontiac that ran 12s

Now with m13 second 350 GTA I get well over 20 mpg. Actually last week I did a mileage check during a fall drive in the country, I got 25 mpg.

Did you ever check if you have a fuel line leak? maybe some of the gas is just being consumed?

Also if you are running really rich, than obviously you are burning through more fuel than needed.

 

A rod/spring change is easy. Theres two hex srews on the top of the carb the hold doqwn two little plates kinda shaped like peanuts, you can see them with the aircleaner off. Unscrew these about 1/4 inch and move these peanut shaped covers to the side. You can see the rod hangers under the cover. Just push down on them like a keystoke on your keyboard and they pop up, use the rod that just poped up to fish the spring out. The rods just unclip from thier hanger from this point.

You should change the jets also, There are 3 little clips holding the plunger LSF of carb, one on the fast idle DSR and the last one is on the PSR for the secondaries. Then just take all the screws out of the top and it pops off. Lay the top upside down on a clean flat surface look in the carb and there will be 4 jets 2 in the front and two in the back just unscrew them and replace them with 92's all the way around and reasseble the carb. This should lean you out enough to improve milage.

 

thank you everyone for all the good ideas, i think i'll be ordering all the pieces here today or tomorrow and see how that works, thank you and i'll be sure to let you know how this turns out..




nathan vetter

 

OK, yes all of you give very good points and I will be checking into everyone of your ideas, but see I'm a little shaky on the timing crap and all that stuff because of the fact that I had a TBI setup and my mileage all of a sudden went to crap, and that was back when nothing on the car had been fooled with. Now I have a carburetor setup and HEI distributor that is all BRAND NEW equipment just put on within the last two months. The weights on the distributor moved lovely and so forth on all of that.

I totally agree with checking the timing and making sure its advanced but the whole deal is this mileage problem just started all of a sudden basically when I had my TBI setup. Half a year later I changed to the carburetor setup and the mileage problem continues. That is why I feel it has to be something other then a timing problem and there are brand new AC Delco plugs with 8 MM wires, and brand new 02 sensor and so forth. I mean is there anything else that could cause this besides timing being off because like I said it just all of a sudden started and the timing had never been touched or fooled with when I had the TBI setup and there was no vaccum advance, then I went to carburetor setup problem continues so I'm sure its nothing with that. I know this is long and seems like I'm not listening to your ideas, but I feel that its something more then that, anyone kinda understand what I'm saying and can help me out a bit more or should I say forget it ? Ya I have 145 miles on this tank right now and I hafta go fill up right now, it really sucks !

 

If it started all of a sudden then we need to look at a couple things that would cause a milage drop. One would be the EEMS "the computer" or componet of. Componts are everything under the hood with a wire or vacuum line they all serve a pourpose to provide the correct adjustments to keep your car running effeciently. Now that that system is no longer serving a function........... wasted money on an O2 senser since its not being used anymore, the carb doesent see it. You still dont have good fuel econmoy with that system eliminated so it may not have been a problem. The other would be a mechanical probelm worn rings, loose timing chain, improper valve sealing ect.......
I still beleive there is room to grow here with the carb setup. It needs to be jetted for your engine 305! This is where its easyer to have a holley. Ive bolted stock cal 1406 edelbrocks on fairly stout 350's and theve ran pig rich durring cruise then they ran the same on some stock 350's as well. This is why you need to properly jet your carb. A vacuum guage can tell alot about an engine. It can be used to set timing, adjust idel mixture on your carb can give indications of all kinds of mechanical problems. It's a carb owners best friend. I highly reccomend you buy or borrow one for the durration of your problems, it can help you to figure out what might be a problem and can give us a better idea of how your engine is running so we can give suggestions.

 

I realize that i need to rejet my carb for my 305... man none of you have ever seen a car run so rich not something to brag about though...haha.. but does anyone know what i need to step it down to like what rods or what i need to step down... i've been emailing an edelbrock technician about this and im still waiting for him to get back to me on what i need to rejet too....

about that vaccum gauge... where am I wanting to hook this up at ? ? i got a mess of vaccum lines and so forth, which ones do i need to put the gauge on and do i need to check them at idle or part throttle and so forth,, what kinda readings should i be looking for and so forth ?? i'm not all up on vaccum readings and how to do them so bear with me here as i figure this stuff out.... but i do have a vaccum gauge and i'm awaitin any further instructions... thx..

 

You want to hook the vacuum guage to the full time source in the drivers side front of your edelbrock, the passenger side ported source should be plugged into the vacuum advance on the distributor.

This is what you should do when you get a vacuum guage.
Plug the guage in the full time vacuum port and get a reading.
It should read a minumum of 18in with the car running fully warmed up choke open. Adjust the timing with the vacuum guage, advance the timing until it maxes out then starts to drop, return the distributor to max vacuum and then retard the timing until you get a 2in drop. This is where you want to be timed at.
Then adjust the idle mixtures screws "IMS" on the carb for best vacuum. Shut the car down and screw both the IMS clockwise until the stop lightly, then turn them both 1 1/2 turns out counter clock wise and fire the car up. From this point pick a IMS screw and turn it clockwise slowly, watch the vacuum guage if vacuum increases then your going the correct way if it decreases set the screw back to 1 1/2 and go counter clockwise until the vacuum maxes out and starts to drop. Set the screw back to the max vacuum point and adjust the other IMS to match the nuber of turns this one is at make a not so you dont forget. Now if the idle speed has changed adjust the idle speed screw back to the point where the idle is normal. Make a note where the vacuum guage is reading now. Now try to adjust the timing the way I described again and see if it changes, if you now get a higher reading then before max the timing and back it off two inches of vacuum. Now from the point the IMS are at now turn one clock wise to see if the vacuum reading increases if yes then max vacuum it out then adjust the other IMS to match, the idle should increase again so adjust the idle screw to the correct idle. If you turned the screw clockwise and the vacuum dident increase turn it counter clock wise until you get max vacuum and mtach the other screw to this point then adjust the idle screw to the correct idle.

This will set your timing and idle mixture settings it will help reduce some of the fuel consumption at idle and may help off idle a bit if the timing wasent set correctly by the shop, they may have set your timing by a general number they set all distributors by 8*, 10* 12* or so on. This type of general setting doesent work for every engine the vacuum guage sets it for the condition of your engine.

As far as the jets and rods edelbrock may have a good suggestion that will be in the ballpark, I still think you should be about 8% lean by the book for a base setting. From this point you should be able to jet down and increae fuel economy even more.

 

Thank you so much 'SSC', I'm sure that took alot of time to write but I greatly appreciated it. The Edelbrock technician recomended that I go to these Jets and Rods.

PRIMARIES
Jets: #1425 (.092)
Rods: #1453 (071 x 047)

SECONDARIES
Jets: #1424 (.089)


So as we speak there on order and should be in next week. As soon as I get them installed I will go through all that you just guided me through, honestly I didn't really know much about this crap but the way you just explained it kinda made it click for me, thank you so much for all your help and to everyone else who has posted in assisting me. My local parts store said the jets will be in Tuesday but the rods for some reason were a special order so they probably won't be in till Thursday so probably next weekend I'll get them installed and hook the vaccum gauge up and start getting things set. Again thank you for that big explanation, I bet your pry exhuasted after typing all that but its very helpful. I'll be posting again on here if I encounter any problems while setting all this.

Quick question for you SSC or anyone, when you were talking about the vaccum lines going into the carburetor I wanna double check on what sides now. Here is how I have it set up right now. If your standing in front of the car looking down at the motor the vaccum line from my vaccum advance on the distributor is going into the right hand port, and the left hand port is going into the container behind the right hand headlights. Remember all my rights and lefts are from standing in front of the car looking at the motor. Thanks again for all your help everyone !




nathan vetter

 

I get 10 MPG :-\ I'm getting code 32 though. How hard is it to replace 02 sensor and EGR? I'd like to do that!

 

O2 sensor isn't to bad to do, you can't get a ratchet on it unless you were to cut the wire and plug from the the sensor itself and then re-wire it once its put in, otherwise hope you have a short 7/8 wrench, one that will fit down in that little area, a big one is to large obviously because all the brake lines and emission lines prevent you from having enough room to move the wrench back and forth.

First if you have a ratchet and socket that will fit on there good and gives you enough room cut the wire to your old 02 sensor right by the sensor and then unplug the connector to it and toss it. Use the ratchet and take the old one out, ratchet will save ya time.

Second start screwing in your new 02 sensor as far as you can by hand then get a short 7/8 in. wrench and wrench her tight. Next plug the wire back into the connector.

Third pull the negative terminal off the battery so the ECM clears its self of the SES light and then re-hook the terminal and your set to go.

I have a 1991 305 and well thats how my 02 sensor is setup, its positioned on drivers side pipe... not sure how it is on other setups but thats how mine is.

Not sure on your other question bud, sorry.



nathan vetter

 

You can buy/borrow an O2 sensor socket from autozone. Just FYI.

 

WOW, I feel so dang stupid, haha... man I just got the biggest laugh of my life... I never knew they MADE SUCH A THING ! ! ive had to replace mine twice and man i end up b*tchin the moon out back and forth on the crap and here i coulda done that.... and to think i've been doin the hard way all these times... thx ground rat,,, had no clue there was such a thing...

 

Not a problem were all here to learn and help when we can.

From you view point left is right and right is left. Passenger side should be right and drivers side should be left, on cars prespective is from the drivers seat looking out the windshield.
So you have the vacuum lines on carb mixed up. Just remove the drivers side vacuum line and plug it for the time being, this is a full time source. You want the distributor vacuum advance on the passenger side port. You will need to adjust your idle once this line is swaped around to the proper location.
You may need to advance your timing as well since the way its hooked up now it goes full vacuum the second you start the car and not progressivly off idle like it should.

 

now the big question, how much $$ is a new o2, and where is the cheapest place to buy?

 

thats the simple question ERROR 404... Just go to your local O'Riely's, Napa, or any kinda name parts store and they will have what your looking for. Prices are approximatly -

AC DELCO - $41.11

BOSCH - $21.62

AUTOLITE - $31.79

hope that helps out, you should be all set to go now !

 

is there any difference/reliability between the 3? there is quite a price gap there, but all 3 of them are cheaper than I would have guessed, I guessed around $60.

 

Try THREE mpg!!!! At $4 a gallon now!? Hi. I'm totally new here, so much so that I can't even find where to POST a new message in a topic!!! My 85 Z28 is quite ILL. Started with surging at all speeds. Even 70 on freeway. Had been having my gas caps stolen.....1, 2 then on 3rd- bought locking...thought that had fried fuel pump...a friend of a friend who was suppose to be an ACE mechanic looked at it and said it was my CARB. He did some adjusting. The surge stopped....BUT on way home from the adjusting, started losing power on freeway-BAD. Took exit, and before I made it to bottom of offramp, 3/4 of a tank of gas disappeared! I watched the guage go to empty! Opened the hood to find PUDDLES of gas everywhere. Towed it back to the guy, who said the carb was SHOT-& he could rebuild it. Gas got into the oil...plugs fouled... black SOOT was shooting out the tail pipes! Got the kit, then was told wasnt enough-needed another carb? He got 1, but it ISNT the same carb...vacuum connections seem different? More than before. Had an 85 E4ME Rochester model 64-70087....he put on an 88 E4ME but model 17088204, 1463 FRB??? The MC solenoid has no insert- would that matter?
$500 LATER, it still runs WAY TOO RICH....MASSIVE FUMES in driver compartment and feel like the vacuum is mixed up somehow because of the extra ports on the carb? I work on my car but I am carburetor clueless!!! It also is missing the Baro sensor-not sure if that matters, and Check Engine AND Choke lites are both on. Have been for months BEFORE this. Only error code was 41, which tells me to reference x1, EGR failure. That aside, the fuel smell and gas milage are killing me! And, hate to think what the smog test thats due in June will show. Any body got any idea? AND - can someone show me the proper way to post? Thanks! (From what I've read here - you all are more knowledgable than ANY shop or ACE mechanic I've encountered!

 

i would make sure that your choke is not sticking, the butterfly valve at the top of the carb. when the engine is warm, it should be completely open.

I would also make sure that he floats are adjusted properly. i am not shure the exact details on this for a rochester carb, but there should be sight plugs, or windows. there will be a ajustment screw on the bowl, and the gas, while engine is idleing, should be juss to the bottom of the sight. maby someone with more rochester experience could chime in here.

another possible cause, but i dont feel the whole cause, would be the ignition timing is off (severly reatarted) and is not burning all the fuel.

bad cap/rotor, or spark plug wires can also affect this slightly.

 

Didn't read the whole post, but figured I would chime in. This info is a little irrelevant, but my 91rs with 305tbi gets 23.5mpg with minimal mods. It is currently at 227,000 miles, but I like to keep it maintained. All the more I have done to it is put on shorty headers and hollowed out the cat, ripped off emissions and threw away the stock air cleaner for an open element. Also put on MSD blaster ignition coil. Everything else is stock with no code problems. Keep in mind that I have to drive my car approx 70 miles daily.