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66 Dart with poor gas milage
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Author:  customgreen [ Tue Jun 19, 2007 6:15 pm ]
Post subject:  66 Dart with poor gas milage
I am new to this forum but not to Mopars or slants per say. I have to admit that I have lost my way regarding this car and it's performance. I have been so tuned into big block Mopars for so long that I have forgot all my slant six knowledge. Here is my problem. I have been driving my daughters 66 Dart GT since she gave it back after spinning two main bearings. I picked the car up from her and basically parked it for a couple of months. I didn't have time to mess with the engine so I asked a friend if he could help me out. He had a 225 slant from a 71 Dart that he would set up for me and stick in the car. He used my head from the 66 225 and got the engine running decently. I drove the car off and on for a couple of months just around town. It needed a few things that I was able to do when time allowed. New radiator, new motor mount, gas tank seal (for the inlet tube) front and rear shocks, and a new Holley carb. Now I am driving the car on a regular basis to try to save a bit on fuel. I am finding out two things. The car sucks gas like a pig, and it wants to stall constantly when I start up from a stop. I have the timing dead on, (as far as I know) and the distributor seems to be o.k. (vacume advance seems to be working o.k.). The engine has a new timing chain, new points, new condenser, and a new coil, cap and wires and rotor. Gas is clean, new fuel pump, and new gas lines from the tank. I would like to get this car to get around 22-25 mpg (right now it's at 15) and better perfomance from a start. The rear end is an open 2.76, and the car has 14" tires. What can I do to help this old girl out? If it were a 383, or 440 I would be all over it, but I seem to have amesia when it comes top the slant. I should be able to get it straightened out I have had a ton of them way back when, but I am stuck. Any suggestions? Any and all suggestions are appreciated.
Author:  SlantSixDan [ Tue Jun 19, 2007 6:24 pm ]
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Let's focus in on this "new Holley carb". Is it new-new or is it a "remanufactured" unit from a parts store?
Author:  customgreen [ Wed Jun 20, 2007 6:25 am ]
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The new Holley was a new unit that I bought from NAPA. The old Holley was leaking badly and new gaskets didn't help it out. The old Holley as well as the new one are doing the same thing (bogs out to a stall from a dead start unless you play with the gas pedal) It makes me think that I either have a fuel delivery problem, or timing issue. Since I live in Florida and we are at sea level, possibly the carb is jetted wrong? The Holley that is on the car is a weird style. It uses the "twist" throttle linkage. The other slant car that I drove was a 66 Belvedere II and it got very good gas milage, but it used a Carter carb, which will not work on the Dart. Like I wrote yesterday I am a bit lost with the slant.
Author:  SlantSixDan [ Wed Jun 20, 2007 7:08 am ]
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NAPA don't sell new carburetors, they sell "remanufactured" ones which, like all "remanufactured" parts—especially carburetors—are trouble-prone junk. See this thread for more detailed information. So, you have in all likelihood replaced one bad carburetor (worn out and leaking) with another (irretrievably damaged in the "remanufacturing" process).
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bogs out to a stall from a dead start unless you play with the gas pedal
Have you checked to make sure your distributor vacuum advance isn't blown, and that its vacuum hose is in good condition? What is your initial timing set to? Pull a few spark plugs and look at their tips, what colour are they?
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Since I live in Florida and we are at sea level, possibly the carb is jetted wrong?
No.
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The Holley that is on the car is a weird style. It uses the "twist" throttle linkage.
Used on A-bodies with slant-6 engines from '60-'66 except '65-'66 with factory A/C.
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The other slant car that I drove was a 66 Belvedere II and it got very good gas milage, but it used a Carter carb, which will not work on the Dart.
Certainly it will -- as long as it's got (or is fitted with) provisions for the rotating-rod type throttle attachment.
Author:  Doc [ Wed Jun 20, 2007 11:47 am ]
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The SL6 is no different than a V8 when it comes to the distributor tuning and carb adjustments...
One area that is different is mechanical valves, I would double-check the valve lash adjustment. Mis-adjusted valve lash kills performance and MPG on a SL6. It is better to have the lash a litttle loose than tight so pull the valve cover and check the lash before doing anything else. (Spec is .010 I & .020 Ex but target .011 I and .021 Ex to start.) Looser will help manifold vacuum.

The distributor is next on the list. Is the mechanical advance working? is it coming in quickly? The off idle stalling is a sign of stuck or slow mechanical advance so check it. Also advance the initial timing, it should be in the 5 to 8 degrees BTDC range.

Last step, carb adjustments. Dan hit it with the rebuild carbs, usually they get crappy MPG because of drilled out main jet - crappy workmanship. Let's get through the first two steps before 'digging into' the carb.
DD
Author:  Aggressive Ted [ Wed Jun 20, 2007 2:25 pm ]
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The guys are right on!

Do you know if you have a 1920 Holley or a 1945 Holley? If you have a either one I can help. On thing I found is that if the power valve in the carb is stuck, they will drink lots of fuel and stumble like you mentioned.

I am trying to get past 22. 5 mpg myself. I drive 120 miles a day!
25 mpg would be nice!
Author:  Sam Powell [ Wed Jun 20, 2007 4:23 pm ]
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My favorite focus to improve economy is to improve the condition of the primary ignition wires. Between the alternator and the coil are many plug in connectors that get resistance in them, both in the connector, and in the crimp joint holdingn it to the wire. Over the years this builds up to the point where you lose a volt or two along the line, and this will cost you big time. For some reason the Mopar ignition really needs to be in top shape to be efficient.

Put your VOM on the alternator out put, while the engine is idling and check the voltage. It should register 13.5 volts. If it does not, then start with your charging system. Then put your VOM across the high side of the ballast resistor. This would be the side with two wires ganged together, usually brown and blue wires. If the voltage is any more than .5 volts less, then you are losing alot along that system. One of the problems could be the old ameter in the dash. Everything must travel through that, and they are nortoriously bad after many years of use, or just sitting. I installed a voltmeter in my car, and skipped the ameter altogether. This includes the crusty old bulkhead connector as well.

When I replaced all the primary ignition wires, and the connectors, my gas mileage went from 13 to 18; no kidding. And my car is likely heavier than yours. These other suggestions absolutely must be checked out as well. There are many places for things to go down hill that may need to be fixed up, and which will yield improvement, but this one is often overlooked, and pretty cheap.

Sam
Author:  Timmy! [ Wed Jun 20, 2007 7:40 pm ]
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Yeah, that's pretty pathetic MPG, but don't despair. These cars are designed to get well over 20 MPG.

My stock '64 Valiant with 225 engine and 176K miles [only add-ons are larger exhaust and Pertronix] averages 23.1 MPG so far this year. It's a 3-speed with 3.55 rear end and Carter BBS carb. Daily commute to work is 15 miles through 28 traffic lights at 40 MPH. Drive home is 20 miles on the Interstate at 55 MPH.

My previous car was a '63 Valiant 170 automatic with 3.23 axle and Holley 1920, which was even better. I could get 25-27 MPG at 55 MPH easily with points and condensor. Rust precluded me from hanging on to it.

Some things I've learned to pay attention to for maximum MPG are:

1) How much lift you have at the bowl vent.
2) Manifold vacuum.
3) Driving technique.
Author:  customgreen [ Thu Jun 21, 2007 4:42 am ]
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For some reason my replies are not getting through. Most likely my computer! The plugs that I have in the car are Autolite 65. They are clean and a darker brown color. No deposits of anykind. All plugs look the same. The itial ignition timing is 2 BTDC. The carb has been "leaned" out as much as I can (with same results). I am not sure what the dwell is set at. I loaned out my dwell/tac meter and have not gotten it back yet. Points are set at 20, plugs at 35. Distributor advance seems to be working correctly. Diaphram holds suction, also the timing light shows it working. Carb choke (heat stove) also seems to work well. Kickdown works well. Car idles good but not perfect (a little rough) I am thinking it might need a valve adjustment. The valves were adjusted about a week after the engine was put in. Since then it has had about 500 miles put on it. No obstructions in the exhaust. No gasket leaks. No rubber hose leaks. Manual brake car so no booster leaks.
The carberator that I bought is a 1920 Holley. I went to several different places to try to find one. Only NAPA had a listing. They did not want my old one as a core. When I got the new one it came in a Holley box and had "new carberator" on the packaging. Wether it is a new one or reman I don't know. I did have to put my "twist" linkage on the carb because the new one did not have it. The Carter that I also have from my Belvedere II will not work at all. Different linkage and different fuel inlet location.
The car does seem to improve when it warms up, but it still will stall out from a standing start if you are not very careful. My biggest concern is the gas milage. The stalling is also a pain and I am sure they are both related. Basically I feel that the car needs better tuning that I have done so far, and possibly a valve adjustment. I have my distributor from my Belvedere that I can pop in to see if it will work better. The Belvedere did not have any of these problems when it was using the slant. When I drive the car (which is fun to drive) I keep my foot out of it. I take it easy and don't wind it out at all. I feel that the car should get at least in the low 20's for milage.
Author:  SlantSixDan [ Thu Jun 21, 2007 4:28 pm ]
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Quote:
For some reason my replies are not getting through. Most likely my computer!
Naw, there's something the matter with the board. It's in the process of being fixed. Keep checking back.
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The plugs that I have in the car are Autolite 65. They are clean and a darker brown color.
Light tan is preferable, but dark brown tells us there probably isn't anything too awfully out of whack going on in the combustion chambers. Autolite 65s are OK, but next time you put in plugs, buy NGK ZFR5N spark plugs. Remember, whatever spark plugs you buy, to remove the metal ring washers from the spark plugs before you install them in the engine. You will also want new spark plug tube seals -- B45384 will get you a spark plug tube seal at NAPA (you'll need to order six). Or, you can get a set of six from Fel-Pro under P/N ES12794.
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The itial ignition timing is 2 BTDC.
The crank pulley on these engines is a 2-part item, with the outer ring member bonded to the inner hub member with rubber. Over time, the outer ring can slip relative to the hub, and the direction it slips tends to retard the ignition timing for any given indicated setting. You may want to pull the frontmost spark plug and physically check whether the piston is actually at TDC when the mark is at "0". Also, you may want to try a little more initial advance; try 6° BTDC or so.
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The carb has been "leaned" out as much as I can
How? By just twiddling the idle mixture screw? That won't get the job done; it sets only the idle mixture. Be advised, these Holley 1920s can lose their power valve: Years ago, I had an 8-month-old brand-new (not "remanufactured") Holley 1920 on my '65 Valiant that that suddenly exhibited strange behavior: The engine ran very well and had fine power, but was suspiciously easy to start and drive from cold (zero choke required, just hop in, turn the key and drive off without any stalling or gasping...even with the choke disconnected!) and the car was getting under 10 mpg. Turned out the brass seat ring that retains the power valve check ball, had fallen out of the metering block. Result was that the power valve was always WIDE open. I put the metering valve back together and restaked the seat ring, and things went back to normal (20mpg, choke and careful cold driving required).
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Distributor advance seems to be working correctly. Diaphram holds suction, also the timing light shows it working.
Good. How about the mechanical advance system?
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Carb choke (heat stove) also seems to work well.
Good. How about the manifold heat control valve ("heat riser")? Is it free to rotate, or is it stuck? If it's stuck, is it stuck with the rectangular counterweight in a more or less horizontal orientation, or more or less vertical?
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thinking it might need a valve adjustment.
Never a bad idea. valve adjustment procedure.
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The valves were adjusted about a week after the engine was put in.
This is a newly-rebuilt engine, or a used one? What is its history?
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No obstructions in the exhaust
OK, checked how?
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The carberator that I bought is a 1920 Holley. I went to several different places to try to find one. Only NAPA had a listing. They did not want my old one as a core. When I got the new one it came in a Holley box and had "new carberator" on the packaging.
I've known NAPA to sell remanufactured parts under the "NAPA New" moniker, but this is an interesting case you describe. Take a look at the carburetor body surface that faces front or upward, near the fuel inlet, and find the 4-digit number and tell us what it is. Also, do you still have the receipt from when you bought it? What number was it ordered under and how much did you pay? This'll help me nail down what you bought. Napa do offer "remanufactured" carburetors for your application.
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I did have to put my "twist" linkage on the carb because the new one did not have it. The Carter that I also have from my Belvedere II will not work at all.
Yeah, it will.
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Different linkage and different fuel inlet location.
The twist-type linkage piece can be put on a Carter, too, and the fuel inlet location is irrelevant even if you keep the stock pump-to-carb line, and especially if you do the fuel line mod.
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The car does seem to improve when it warms up, but it still will stall out from a standing start if you are not very careful.
Have you checked for vacuum leaks? Carb-to-manifold, manifold-to-head?
Author:  customgreen [ Fri Jun 22, 2007 5:56 am ]
Post subject: 
I did a little more investigating on this engine. As I wrote previously I did not have any spare time to work on the car when it needed the engine replaced. I relied on a friend who was willing to help me out. The engine came out of a 1971 Dart Swinger. The Swinger showed only 78K on the clock but who knows. I know now that it isn't the original engine for the car. I had been in that car several times and the engine always seemed pretty good. I now have looked at the block and found that the engine is a 74 block. The guy who put it in said he didn't look at the block, he just assumed it was a 71. At least thats what he told me. I am thinking now that I might want to do a compression check on the engine. The head that is on this block is the one from my 66 engine. The head off the 74 engine was put on some guys 198 truck mortor (or something like that). The exhaust manifold is one from my 66 Belvedere. The original 66 Dart manifold was craked in half. The exhaust on the car is newer. It was replaced about a year ago when it started to get pinholes all over it. I had the whole system replaced from the manifold back.
I just checked the mechanical advance and it seems a little "gummy". It feels like the weights are not returning completely after speading apart. Hard to tell with the dist in the engine. I am used to big block distributors and how the feel so I might be wrong about this. The heat stove seems to work well. It is free and does work when the car is warmed up. I did put in new spark plug tube gaskets when I did the full tune up on the car. The are not leaking that I can see.
I know what you mean about the two piece crank pulley and the rubber slipping. I did think of that but only for a half a split second. lol. I will bring the engine up to TDC and see where the mark is.
Yes I only "leaned" out the carb by the idle mix screw. The 4 digit carb number is 3276. The carb cost me 130.00.
The reason that I say the carb from my belvedere will not work has to do with the linkage. The Carter carb has the linkage (cable pull) parallel with the drivers inner fender. The Holley has the linkage perpendicular to the fender, or paralell with the firewall. Basicaly the carbs are mounted 90 degrees different from each other.
I had suspected a vacume leak so I replaced the carb base gasket with a new one. The manifold was cleaned and no buggers were on it. Haven't checked manifold to head but I will today.
I will have to brush up on my valve adjustment proceedure. I think the last time I did that was 20 or so years ago on my 65 Barracuda with a 273. Hmmm this should be interesting. lol. I appreciate the help and guidence.
Author:  customgreen [ Fri Jun 22, 2007 9:32 am ]
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I pulled the distributor out and tore it down. Sure enough the weights were not working. The distributor was rusted and gummed up. I did a complete cleaning and light greasing of the whole distributor. I reset the timing to 6 degrees BTDC after playing with the adjuster plate on the bottom of the distributor. It took me a few times to get it set right on the bottom of the distributor. Now the car is acting a thousand times better. No stalling from a start, idles a little bit better (I think it still needs a valve adjustment). Power seems to be about the same. I will check the gas milage as soon as I can. The engine does run a lot better. Thank you for all the help. Progress is being made. Yeah baby!
Author:  SlantSixDan [ Fri Jun 22, 2007 2:19 pm ]
Post subject: 
Quote:
The engine came out of a 1971 Dart Swinger.
Is your '66 an automatic? If so, did you use the 1/8" adaptor ring in the counterbore of your crankshaft before putting the new engine in? The '60-'67 crankshaft counterbore & torque converter nose is 1/4" smaller in diameter than the '68-up, so when using a '68-up engine in front of a '67-down automatic trans, you need that adaptor ring, or you'll create problems with trans front bushings and seals, and possibly vibration issues.
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The distributor was rusted and gummed up. I did a complete cleaning and light greasing of the whole distributor. I reset the timing to 6 degrees BTDC after playing with the adjuster plate on the bottom of the distributor. It took me a few times to get it set right on the bottom of the distributor. Now the car is acting a thousand times better.
Great! Good progress.

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The 4 digit carb number is 3276. The carb cost me 130.00.
Definitely a "remanufactured" unit; that's about what NAPA charge for such an animal. :-( If the box said "Holley II" on it, at least that's one of the less unreliable brands of reman.
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The Carter carb has the linkage (cable pull) parallel with the drivers inner fender. The Holley has the linkage perpendicular to the fender, or paralell with the firewall
Ah, someone installed a 2bbl carburetor setup on your Belvedere! The factory 1bbl carbs all have the throttle shaft running front to back, while factory 2bbl throttle shaft runs side to side. The 2bbl setup can give better driveability and economy when set up well. You may want to look at swapping on the intake & carb at some point, but you'll have to change the '66 Dart to a cable-type accelerator, unless it has factory A/C.
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Haven't checked manifold to head but I will today.
If/when you do a manifold swap, it is very much worth your while to get the good gaskets for the manifolds-to-head and intake-to-exhaust junctions.
Author:  customgreen [ Tue Jun 26, 2007 4:17 pm ]
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The Dart is an automatic car. I have no idea what was done with the torque converter. The car does vibrate badly above 50MPH.
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