By on October 19, 2009

Fie-yuh! (courtesy wefr15.com)

TTAC Commentator ajla writes:

Hi Sajeev, I recently overpaid on my purchase of a 1986 Dodge Diplomat SE in order to save the car from meeting a grim end in the Cash 4 Clunkers program. The car is in good shape and has 98,xxx miles on the odometer. My question is this: The Diplomat has a 2bbl 318 V8, but every single gas station in my part of Florida only sells E10 fuel.  I’ve read that running E10 in a carbureted engine can cause some big problems. If this is true, what kind of trouble should I be expecting, is there anything I can do to mitigate the negative effects of E10, and how long do you think I have until issues start to crop up? Would I be better off just searching out a station that sells pure gasoline even if it’s fairly far away?

Sajeev replies:

And kudos to you for saving a cool car from the C4C program! While it took me about 25 years to consider these final “Dippys” worth more than scrap, I was wrong. No matter how out of touch the Diplomat was to the imports or the freshly minted Taurus, it will never meet the historical fate of the Chrysler Sebring. Ever.

That’s a cool car, much like my 1972 Continental Mark IV. Whose 4bbl Holley operates well on E10 gas. For the past three years, in a hot climate similar to Florida.

So, while E10 definitely sucks, it won’t kill your car. The Mark IV sits for months waiting for the Mehta brothers to pimp the streets of Houston in style, but it never complains. Starts in about two milliseconds, idles great, etc. While your carb is “choked” (get it?) by electronic engine control add-ons, I suspect a full rebuild with new springs and rubber is what you’ll need if performance becomes a concern.

I’ve heard that older cars (and lawn care equipment) benefit from an occasional bottle of fuel system cleaner to proactively treat E10’s side effects: ruining rubber seals, clogging little passageways, etc. That makes sense, and fuel system cleaners are cheap. I’ll occasionally throw a can of Sea Foam in tank for this reason, especially if the car stumbles or stalls when it shouldn’t.

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27 Comments on “Piston Slap: Diplomatic Immunity...”


  • avatar
    Paul Niedermeyer

    ajla: I’ve read that running E10 in a carbureted engine can cause some big problems.

    Where did you read that? Straight gas is almost impossible to find. All old cars are running on E10. I haven’t noticed any ill effects.

  • avatar
    CyCarConsulting

    Your problems are about to become much larger, than worrying about gasoline.

  • avatar
    fincar1

    So far I haven’t had problems with my 84 RX7 and E10 fuel. *crosses fingers*

    Those old Diplomats can be made to really handle. I had a 76 Dart police package car, and have driven an Aspen with that setup, and they do handle well. I hope you enjoy your car, and add my congratulations for stepping up and saving it from c4c.

  • avatar
    ZoomZoom

    CyCarConsulting :

    Your problems are about to become much larger, than worrying about gasoline.

    Was this just an inside joke that you thought would be clever? If so, I didn’t get it, so please expand on this.

  • avatar
    Stingray

    A visit to CarCraft, HotRod, Allpar or a Diplomat forum should help you with the following:

    1) Wake up that 318.
    2) Get rid of the electronic garbage.
    3) Put a proper 4bbl carb there.
    4) Still be emissions complaint if required.

  • avatar
    Stingray

    ZoomZoom :
    Was this just an inside joke that you thought would be clever? If so, I didn’t get it, so please expand on this.

    I’ve read somewhere that the lean burn combustion system Chrysler employed in those cars has some small problems

  • avatar
    Mike66Chryslers

    My guess is, if the car was a runner when you bought it, it’s already had lots of E10 through the fuel system.

    The engine will run a bit lean on E10 with the stock carb settings. Fuel mileage will be reduced versus running “pure gasoline” but compression in your 318 is probably low enough that it won’t cause other maladies such as detonation.

    The E10 may break-down deposits in your gas tank and fuel lines. Change the fuel filter periodically. Remember that there is probably also a screen-type fuel filter built into the inlet fitting of the carb which should be removed and cleaned also. If the car has ever had a gas tank leak which was fixed with a “slushing sealant” in the tank, you should also be aware that most of these sealers are also ethanol-soluble.

    For inquiries about anything specific related to the car, try signing-up on moparts.com or find a Dippy-specific web message board.

    PS: As Stingray alluded to, I’ve never heard anything good about Lean Burn. Mounting the ECU to the side of the aircleaner was a dumb idea. If your car has a Lean Burn ignition system, there are how-to’s online about how to get rid of it.

  • avatar
    john.fritz

    CyCarConsulting :

    Your problems are about to become much larger, than worrying about gasoline.

    Was this just an inside joke that you thought would be clever? If so, I didn’t get it, so please expand on this.

    I’m just trying to figure out what the hell that comma after the word ‘larger’ means…

  • avatar
    TR4

    I’ve used gasahol in quite a few carburetor equipped cars since the 1970s to date. At some time (late ’70s /early ’80s?) the auto manufacturers switched to materials that are not affected by the stuff. The latest vehicle I had gasahol problems with was a 1973 Opel, and possibly my wife’s ’76 Mustang. Our 1985 Astro (last year with carburetor)never had gasahol problems. If you do have problems, it will likely be fuel leaks from rubber gaskets or hoses that “rot out”. Probably though, your ’86 is too new to worry about this.

  • avatar
    ponchoman49

    These are not bad cars at all and much can be done to wake them up. The E10 shouldn’t have much adverse affect short term. I have been forced to use it for the past 2 years in my 1981 Trans Am and haven’t noticed anything different in the way it runs. I do every November dump some Stabil in the fuel when it goes up for Winter so that may help. As for the 318 we used to remove the electronic lean burn Carter 2 BBL carb and find a wrecked cop car in the junk yard with a good 4 BBL manifold and non- electronic tuned Quadrajet carb and install those along with a little more timing for much improved performance over stock with decent highway fuel mileage well over 20 MPG.

  • avatar

    Agreed with everyone here. If you wanna go the modified route, a 4bbl, a real set of heads and a mild cam are perfect for this car.

    (or a late model HEMI or LS-X swap…I’m just sayin.)

  • avatar
    Stingray

    Sajeev

    He can swap some 360 heads there, put as you said a mild cam, 4bbl intake (cop one) a Quadrajet or AFB (again cop spec), some headers.

    He should be getting around 250-300HP.

    I almost forgot, he also have to make some milling, be it the head or the block to bump a little bit the lame compression that engine must have (I guess it must be around 8.5:1).

    Before installing the head, he could do some porting, a nitrous kit just for fun.

    Heck, there are even superchargers for carbureted engines.

    Again, go check HotRod, CarCraft, Allpar… I have one HR and/or CC article about how to soup that thing up. Dino proven.

    It’s a Mopar. That said, HEMI FTMFW!!!11!11!1

  • avatar
    Autojunkie

    As stated above…

    Get rid of the lean burn system. Nothing but problems. A mild cam, four barrel carb, dual exhaust :)

    Also.. keep a few extra ballast resistors (part of the electronic ignition system) in the glove box. When you get a crank/no-start, and you know it’s not fuel-related, swap out that ballast resistor.

    Aside from that, great job! I would love to have one of those myself!

  • avatar

    Stingray : I almost forgot, he also have to make some milling, be it the head or the block to bump a little bit the lame compression that engine must have (I guess it must be around 8.5:1).

    I’ve yet to see where milling stock disco-era heads is worth the money. Machine shop time isn’t cheap, and most of the compression chambers from this era are terrible. Usually swapping to aftermarket or non-emissions OEM stuff bumps up the compression significantly, even if the Dippy has dished pistons.

    Heads and cam all the way, baby.

  • avatar
    windswords

    The perfect sleeper car. Looks like a grandma’s car, but with the right mods could surprise a lot of people.

    “Looking back, the lasting legacy of the Diplomat continues to be visible. Even now, years after the last one rolled off the line in 1989, someone who knows where to look can find a Diplomat still in police duty, and Diplomat taxis remain commonplace, a testimony to the proven durability of the F and M body design. Diplomats still on the road with 200,000+ miles are the norm. Many old Diplomat police cars also still serve in other ways, such as being handed down to Fire Departments and City Services. They continue to get up and serve faithfully despite many years of abuse and brutal working conditions.”

    http://www.allpar.com/model/dodge-diplomat.html

  • avatar

    Interesting that Canada, the land the Republicans feel sorry for because we’ve lost our ability to choose our own health insurer, has greater freedom when it comes to fuel. Here, retailers include ethanol if they want to, and because they want to (i.e. because the market wants it). And, because part of the market doesn’t, at least one oil company (Shell) loudly advertises that one of its fuel grades doesn’t have any ethanol in it at all.

    I suppose the odd road trip to Manitoba is out of the question, though. :)

  • avatar
    dmrdano

    As a guy who often loves the unloved of the auto world, congrats on saving the Diplomat. There might have been worthier candidates out there from a value stand-point, but there is no arguing with the heart.

  • avatar
    Stingray

    I’ve yet to see where milling stock disco-era heads is worth the money. Machine shop time isn’t cheap, and most of the compression chambers from this era are terrible

    Never said to mill the stock heads…

    To help our friend…

    CarCraft

    http://www.carcraft.com/techarticles/ccrp_0401_mopar_318_engine/index.html

    HotRod

    http://www.hotrod.com/howto/113_0304_318_small_block_build/index.html

    Bonus

    http://www.hotrod.com/techarticles/engine/0304_mopar_318_engine_generations/index.html

  • avatar
    TZ

    Paul Niedermeyer :
    October 19th, 2009 at 1:02 pm

    ajla: I’ve read that running E10 in a carbureted engine can cause some big problems.

    Where did you read that? Straight gas is almost impossible to find.

    Premium gas is often ethanol-free. Can’t remember the last time I saw an ethanol sticker on a premium pump at a major brand.

  • avatar
    ajla

    Thanks for the replies. I’m glad to hear that running E10 shouldn’t cause any catastrophic failures.
    ________________

    As far as modifying the 318 goes, I wasn’t planning on it, but the idea of having a slightly built Diplomat does intrigue me.

    Converting away the lean burn system and then adding on a 4bbl and headers shouldn’t be any problem.

    However, I’ve done cam and valve work on a GM 3800 engine before, and I didn’t exactly love it, so I don’t know if I’d really want to tackle that stuff on my own with the Dodge.

  • avatar
    essen

    Autojunkie – ballast resistors! My dad had a Plymouth Volare with the 318 and always had one on hand.

  • avatar
    Wheeljack

    An awesome swap would be a 5.7L Hemi and 545RFE trans from a wrecked Durango or Ram pickup. I’ve heard tell of people getting these for as little as $1,000 – $1,200 if they are patient.

  • avatar
    joeveto3

    Vooooolarayyyyy, Wo Wo Wo Wo!
    Cantaraaaayyyy, Wo Wo Wo Wo!

    My Dad was a Cleveland cop, so we often had these in our driveway. At times, in the 70’s, they were neon green. Really.

    Still, I have fond memories, of what this car can REALLY do. And that’s all I can say about that…

  • avatar
    golden2husky

    The LA family of engines are great from a durability point of view and a workable point of view as well. I, like the other posters, don’t think the crappy gas will be a problem. I did have a leak caused by what I thought was a methanol mix, but that was a 1972 Plymouth model in the 80’s.

    You didn’t mention a real desire for upping the performance, so if the primitive fuel/spark control system works, let it be until it is a problem. If the system is problematic, you can easily eliminate it by replacing the distributor and installing a firewall-mounted electronic ignition module and ballast resistor. Change the carb to a basic non-feedback type and you are good to go. BTW, when the ballast resistor fails, the car will start but die once you release the key. The resistor is out of the circuit when cranking, as full voltage is required to start when there is a heavy load (starter motor) on the battery.

    Should you want to up the output of the old girl, the 318 is rather responsive to upgrades. Headers, head porting, intakes, camshaft are all available for the LA engines at reasonable prices. Most 318s are yanked and dumped for engines with more displacement, but HOTROD managed to eek over 400 HP out of one in their “Junkyard Jewel” series. Should you go for it, don’t forget that a change in the rear end gears can do wonders for upping your 0-60 time and killing your highway mileage. Also, most Mopars have weak motor mounts; these will either need to be replaced often, upgraded, or augmented with torque straps…

  • avatar
    Jerry Sutherland

    These old Dippys were practically bulletproof-old tech,but well tested over decades old tech.
    Good call to save one of these unloved old warriors.

  • avatar
    nikita

    TZ:

    Many places E10 is mandatory in all grades.

    We have an ’86 Dodge Ram Van with the same 318 2-BBL and it starts and runs fine on E10. Those engines have an O2 sensor, computer and electric variable jet in the carb to vary the mixture.

    The only thing necessary for it to “wake it up” is just advance the timing a few degrees.

  • avatar
    armadamaster

    Nice save, had a 1985 Diplomat stripped not equipped and I still miss that car from time to time. Wish I had a building to hide another one in for weekends.

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