318 recent stock valve job with head resurface. factory 273 4bbl intake with NEW eddy 600 performer 1 inch open spacer. small lunati cam 458 lift [email protected] duration 110/106 center line. new stock electronic ignition. factory manifolds with dual 2.5 piped with cherry bomb extremes exit under rear bumper. factory 2?? gears 7.25 rear. stock size 14 inch rally wheels. no matter how i drive it i cant seem to get more than 11mpgs. what gives. too high gear maybe? mostly drivin in country back roads of foot hills of nc. runs great good power and the exhaust is not strong. its killing my pocket.:sad7:
mileage. the harder i try the worse it gets...
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dartjack
Well-Known Member
First off, check your timing. Are you running port vac for the advance? A must. Run as much timing(minus a couple of degrees) as you can without knock. New carbs are a fit all jetting. Weld an o2 bung in one of the ex pipes close to the manifold. Get an old style single wire o2 and wire it into the pass area so you can monitor(dvom) the reading on the hiway. That will tell the story on box jetting. Get a jet and rod kit for the carb. Jet it down till it becomes a pita and go up one step. Did that with a 258 J10 Jeep w/727 and got up to around 17 mpg with it. O2 reading would actually go to 0 cruising and still have good power and no stumble. Drove it a couple of years like that with no probs. Tuning takes planning and patience to accomplish. Good luck!
dodge freak
Well-Known Member
You don't set the timing at 15 or whatever BS number the factory gives. You set the TOTAL timing after the advance is all in. Bet you don't even know what rpm the mechanical advance comes all the way in. Could be around 2,500 rpm, could be all in around 4,000 rpm, is likely somewhere in between.
You want around 32 to 35 degree total timing at high rpm--keep reving the motor up until the timing stops advancing and then set the timing. Make sure the vacuum advance isn't hook up and wear some ear muffs so your ears don't ring all night, lol, Once that is set, then check the advance springs and if both are stock heavy springs, install one light spring. That will allow the advance to come in sooner.
The carb jetting could be too rich also. Was it a used carb? Edelbrocks are neat carbs, you can just switch rods out..I'm tried, hope others can explain more, good luck, with 2.?? something gears you should get better than 11 mpg, I get 12mpg with 3.91 gears if I drive like..normal, lol
You want around 32 to 35 degree total timing at high rpm--keep reving the motor up until the timing stops advancing and then set the timing. Make sure the vacuum advance isn't hook up and wear some ear muffs so your ears don't ring all night, lol, Once that is set, then check the advance springs and if both are stock heavy springs, install one light spring. That will allow the advance to come in sooner.
The carb jetting could be too rich also. Was it a used carb? Edelbrocks are neat carbs, you can just switch rods out..I'm tried, hope others can explain more, good luck, with 2.?? something gears you should get better than 11 mpg, I get 12mpg with 3.91 gears if I drive like..normal, lol
65TerrorCuda
Well-Known Member
Another thing to look at is your fuel pump. A ruptured diaphragm will leak fuel into the bottom end and do nasty stuff. It's not likely, but it happened to my bro's /6 dart: rich running despite tuning the carb, no apparent fuel leaks, sh*tty gas mileage. Dragging brakes, choke not coming off etc., cover all the bases. My 273 has never topped low 14 mpg's in a sub-3000# barracuda despite changing many components(trans, rear end, gears, tires, intake, carbs, camshaft, heads, etc). It's always got 13-14 mpg no matter what and is unaffected by whether I cruise it or race everywhere. Alignment perhaps?
guess next thing to do is buy a different timing light. all i have is onr for static timing. also gonna order a calibration kit for the carb. picked up a little 4banger last night for a few hundred needing power steering pump. hopefully that will work out and help me save money for the items listed above lol
Have you checked all the very obvious: brakes dragging or adjusted too tight, parking brake dragging, tire inflation, bad A/C clutch, etc. Any dead bodies in the trunk adding weight? Will the car roll in neutral? Instead of buying a different timing light, you may be able to just mark the balancer at 30-40 degrees.
dodge freak
Well-Known Member
You don't want those adjustable timing lights, they just dont seem to read correctly.
You need some timing tape and use it as a guild to mark 35 degrees and use that mark. White paint works good, draw a straight line on the damper. The tape won't stay on, so just stuff it in your tool box.
Then rev the engine up and watch the mark you made. Keep gunning the engine to be sure the advance is all in. Like I said, gun shooting ear muffs are great for your eardrums
Set it at the 35 degree mark and if it pings back it off a tad. Better to have a bit less timing, then a bit too much.
Yeah these old cars can be hard to get good mileage. They drink fuel like its water
You need some timing tape and use it as a guild to mark 35 degrees and use that mark. White paint works good, draw a straight line on the damper. The tape won't stay on, so just stuff it in your tool box.
Then rev the engine up and watch the mark you made. Keep gunning the engine to be sure the advance is all in. Like I said, gun shooting ear muffs are great for your eardrums
Set it at the 35 degree mark and if it pings back it off a tad. Better to have a bit less timing, then a bit too much.
Yeah these old cars can be hard to get good mileage. They drink fuel like its water
thanks all. how do you use the timing tape? put it at 0 deg and just mark at 35-40? ill get some timing tape from summit when i order the calibration kit for the carb. time to let her sit till gas comes down just weekend cruises when im actually home on the weekend.. until then i picked up a 98 z24 cavalier for $300 a set of used tires and a little power steering fluid and a total of 520 dollars.
The two things that jump out at me most here are the carburetor and the open plenum spacer. Those Edelbrock carburetors are not made for mileage. With a square bore design, they just are not the best for mileage. Plus, with that open plenum spacer, I think you are killing yourself on the bottom end....basically the WHOLE operating range of that engine. A spread bore carburetor with small secondaries with NO spacer would probably benefit both mileage and performance by a good margin. Of course, that will require a manifold change, which I am not sure you are willing to do.
X2 bigtime........Artie
I don't know. If you can tell us a little more about the engine, that would help.
C130 Chief
Mechanical Genius
The advance mechanism in your distributor does work, right? Test the mechanical advance by turning the rotor clockwise by hand. It should move about 15 degrees and spring back when released. The vacuum advance is tested by using a handheld vacuum pump/gauge. These are pretty cheap at Sears or HF. The vacuum advance should be connected to the ported (passenger side) nipple on the front of the carb. Once you determine that the distributor is in good health, experiment with advancing the timing. Don't even bother with a timing light. Rotate the distributor body counter-clockwise a few degrees (move the nipple on the advance can about 1/4-1/2 an inch) and test drive. Repeat as needed until the engine pings, kicks back against the starter, or you have a notable power drop. If you ever heard an old timer talk about "timing by ear" that's what you just did. It'll get you in the ballpark. Once you have it where you want it. a couple dots of white paint; one on the damper one on the timing cover, will make a good reference.
Next make sure you don't have a vacuum leak anywhere. Might as well launch the open spacer too. It won't help you.
Now, we'll tackle the carb. Read the book that came with it!!! First check the float level setting. You need to pull the top of the carb, but it's nothing cosmic. Next, make sure the metering rods are all the going down all the way at idle. There are little doors on the top of the carb to access these. Then, and only then would I start monkeying with the rods/jets. There's a handy chart in the book that came with your carb that explains it better than I could. Try setting the primaries one step leaner at cruise. I'm assuming the carb is halfway close out of the box. If the best idle occurs with the mixture screws 1 1/2 - 2 1/2 turns out from seated, it's pretty close.
Yes, you should consider a different intake. The 273 piece was pretty awful. There are plenty of used Edelbrock Performer intakes on eBay for reasonable money. The 273 piece isn't totally worthless however. When fitted with an appropriate length of chain they do a pretty good job of keeping small craft from drifting across the lake.
Next make sure you don't have a vacuum leak anywhere. Might as well launch the open spacer too. It won't help you.
Now, we'll tackle the carb. Read the book that came with it!!! First check the float level setting. You need to pull the top of the carb, but it's nothing cosmic. Next, make sure the metering rods are all the going down all the way at idle. There are little doors on the top of the carb to access these. Then, and only then would I start monkeying with the rods/jets. There's a handy chart in the book that came with your carb that explains it better than I could. Try setting the primaries one step leaner at cruise. I'm assuming the carb is halfway close out of the box. If the best idle occurs with the mixture screws 1 1/2 - 2 1/2 turns out from seated, it's pretty close.
Yes, you should consider a different intake. The 273 piece was pretty awful. There are plenty of used Edelbrock Performer intakes on eBay for reasonable money. The 273 piece isn't totally worthless however. When fitted with an appropriate length of chain they do a pretty good job of keeping small craft from drifting across the lake.
All good advice above. I get 20 mpg with OD manual transmission and 3.55 gears for about 2.60 final drive. I am running the stock 4 barrel intake and carb. The stock manifold is not your problem. Check vacuum advance since that can also leak as well as not advance the timing. Timing is set with the vacuum advance unplugged and carb port plugged. Or TOTAL advanced per Dodge Freak above. Jetting is next, I'd start with larger diameter metering rods. 273's are very efficient. Something is wrong with your setup. Good Luck...
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dodge freak
Well-Known Member
dodge freak
Well-Known Member
yes, all you do. Now the marks might be off 2-3 degrees but it gets you close.
Oh wear gloves when you turn the dist with the engine running. You don't want to get a shock.
Once its at 35 degrees and if you have the idle screwed turn in tight so the egine speed is a steady 3,500 or so. Start advancing/retarding the timing slowly. You will notice the engine speed speeding up and slowing down. You should also notice that as you hit 35-37 degrees the engine speed starts not speeding up as much, if octane is good, you want it set at about once the engine speed seems to start holding steady and back the timing off a tad.
Its called timing by ear. You can listen and set the timing with no timing light. Good idea to have a light to double check yourself.
Oh watch out for the FAN. You don't want your timing light wires to hit it, don't ask how I found that out
omahamoparguy
Well-Known Member
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I would switch to a eldevrock performer with the spreadbore pattern. Then I would use a Q-jet and tune the primary side for fuel econmy. (BTW, Q-jets were used on mopars from the factory)
Look for a mid eighties dodge 3/4 or 1 ton van. ) I know it sounds like blasphemy to put a Rochestor carb on a MOPAR, but when tunen right, you cant beat them for fuel milage. Even the promary rods are adjustable in the Q jet for fine tuning the jetting. You can raise and lower them! OH well just my .02 worth. I used to get 18 to 20 in my 72 demon with a 318 and a 2bbl stromberg carb.
Look for a mid eighties dodge 3/4 or 1 ton van. ) I know it sounds like blasphemy to put a Rochestor carb on a MOPAR, but when tunen right, you cant beat them for fuel milage. Even the promary rods are adjustable in the Q jet for fine tuning the jetting. You can raise and lower them! OH well just my .02 worth. I used to get 18 to 20 in my 72 demon with a 318 and a 2bbl stromberg carb.
the idle screws are set at around 3 to 3.5 turns out or it wont idle. gonna calabrate the carb and and get some timing tape and go from there.what is meant by miving the nipple on the distributor? rotate the dizzt itself? its new also.
i read this the other day and my first thought was that your
exhaust pipe diameter is too big for your 318....fine is you drive around at 5,000 rpms
but that is impractical....torque moves weight...
bigger is not always better...in carb size and exhaust and will result
in a bottom end torque loss...your gear, 2.7x?-2.9x is good for hiway but the overall combination is mismatched for milage
as noted above, some folks ARE getting good milage with the 318
exhaust pipe diameter is too big for your 318....fine is you drive around at 5,000 rpms
but that is impractical....torque moves weight...
bigger is not always better...in carb size and exhaust and will result
in a bottom end torque loss...your gear, 2.7x?-2.9x is good for hiway but the overall combination is mismatched for milage
as noted above, some folks ARE getting good milage with the 318
dodge freak
Well-Known Member
And chance the intake exhaust heat is block. Unless you live down South, way down, Its best to have a heated intake I found.
Rcuda2
Well-Known Member
You said the idle screws are backed out 2 1/2 to 3 turns to get it to idle - 1 1/2 turn out is closer to what it should be. With the cam you have, I'm guessing that idle vacume is low. That lets the carburator jet needles lift - not enough vacume to hold the needle down in the jet. If this is what is going on - use lighter springs under the needle rod pistons or clip a couple of coils off. That will let the needle rods be lower in the jet at idle and also at cruising speeds - leaner fuel mixture - better milage.
makes sense to me. i have another old performer thnk ill try cutting the springs and see if that helps. i didnt think my cam was that big. i do know that since i changed the cam my heat controls are very sluggish to change vent to defrost. it the rain stops ill give it a try tommorow.
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