Any ideas to improve stock 400 engine on Newport?

Engine, Transmission & Driveline

  1. Henrius

    Henrius Member

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    Got a 1972 Newport with a 400 engine. By this time, they had detuned the engine and lowered the compression ratio to meet solution standards.

    I want the car a good street driver, but with more power and more fuel efficiency if possible- but still maintaining a good idle.

    Got any ideas besides raising the compression ratio? Would going to dual exhausts be worthwhile? I would not be opposed to going to headers, either. Would a later transmission that locked up in 3rd gear be worthwhile?

    I don't think I ever got over 14mpg on this heavy car.
     
  2. C Body Bob

    C Body Bob Old Man with a Hat

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    A lock up converter trans, Good Thermoquad carb on factory intake & freeier flowing exhaust will show small but noticeable improvement in both. With today's fuel I'd leave compression alone. Slightly thinner oil can help a bit too. Make sure your air filter remains clean & proper air psi in the tires.
     
  3. twostick

    twostick Well-Known Member

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    2.5" duals for sure. No turbo mufflers unless you like drone at cruising speed. TTI is about the only off the shelf 4 into 1 header and they are spendy but they fit. Their exhaust kits are good too and a little spendy but again, they fit.

    Electronic ign if it doesn't have it already with the advance curve tweaked.

    Advance the stock cam 4 degrees for more bottom end torque.

    A well tuned Thermoquad and a set of 3.23's out back and it should act pretty sporty and maybe a couple MPG better when driven for MPG.

    Kevin
     
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  4. Turboomni

    Turboomni Senior Member

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    Well if miles per gallon is a problem get a corolla. My 440 gets 11 mpg in town and 15. something on the highway with 3.23 rear. If it has a single exhaust go dual. What is the rear end ratio? I personally would do a dual exhaust first. I think headers would be a pain depending on what you want from the car. With gas today and who knows what it will be tomorrow don't up the compression ratio unless you want to be a high octane junkie. Dual exhaust and maybe a better rear end ratio if needed i would think for starters. My opinion only!!
     
    Last edited: Jul 16, 2017 at 11:06 PM
  5. 70bigblockdodge

    70bigblockdodge Old Man with a Hat

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    Dual ehaust, a good tune up, ignition timing tweaks if you are not opposed to opening it up I would change the timing chain, do a leak down test and good valve job with some new valves or at least remove the lip off stock valves and some port clean up with die grinder.
     
  6. 73Coupe

    73Coupe Active Member

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    Slightly higher compression would give better performance and economy. Wouldn't that be worth it for a concession of using at least midgrade gasoline?
    For the owners of 1970 and older engines, is it really that bad to deal with?
    I've got the real low compression in mine (440), I think 8:1? It sucks. 10 mpg, city or hwy. Comp. ratio will be going up slightly when it gets rebuilt eventually.
    2.76 gears too, wtf....
     
    Last edited: Jul 17, 2017 at 6:44 PM
  7. BeatersRus

    BeatersRus Active Member

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    for a start,id install 3;23 gears,a dual exhaust system of no more than 2.5 and No headers!
    headers sound great and they add maybe 7-14hp.
    But they also add a Tremendous amount of Heat under your hood,
    which isnt good for any of the components.


    recc:
    timing chain
    Torque /low-midrange Camshaft w lifters.
    a decent alum intake but Watch your Hood Clearance!
    translation,dont get the Rpm,its too tall.
    new fuel pump
    new waterpump and housing.
    new thermostat.
    complete tuneup,new plugs,wires,cap,and rotor.
    keep the transmission you have and service it.
    if in good condition,get a shift kit and install that as well.
    keep in mind the better it shifts,the less wear and heat in your trans.
    make Sure you keep the Kickdown linkage <<

    have your carb inspected/rebuilt,a good thermoquad is what i like to run on these.
    and hey,they are factory too!
     
  8. Yatzee

    Yatzee Active Member

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    One thing that no one here has mentioned is a decent torque convertor. 2500 stall has just too much slip and they cost money in poor fuel economy because of it. I'd go at least 3200. You need to get the compression ratio up a bit say 9 or 10 to 1. That's going to cost you unless you shave the heads or use thinner head gaskets (redneck solution). Let's face reality, carbuerators are dead, yes dead. They're being replaced everywhere with TBI and give power on demand, easy starting and near perfect fuel to air ratios. May cost a bit but it's money in the bank. A quality carb is not too far off the cost of TBI and if there's two positive changes for performance and drivability this is one and the torque convertor the other. Headers do not create heat in the engine compartment, they literally blow the heat out the exhaust. Now a couple 20 lb cast iron manifolds, they not only create heat but maintain it long after the engines shut off. Possibly it would be cheaper for you to find a good used 440 and install that, preferably one before the emission years. Your performance will go up but as far as mpg, not so much so. I think you need to be real about what it is you wish to achieve and have a good look at your bank account. Speed and performance cost big time.
     
  9. Turboomni

    Turboomni Senior Member

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    I wouldn't mind 9 to 1 compression ratio over what I have. And it wouldn't be a big deal like 73coupe said. The OP has posted once and I would like to know how much time and cash he wants to throw at this thing right now. I would also like to know his present rear end ratio.
    If he wants something to push him back in the seat and went from a 2.78 to a 3.23 or 3.55 even with a good tune and dual exhausts that could be done for relatively little money and idle good. If he has 5000 to dump in it that is another can of worms.
     
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  10. bajajoaquin

    bajajoaquin Well-Known Member

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    It's almost never worth it to make a change like you're talking about in order to save money on gas. Do the math. A new carb is going to be a few hundred dollars. TTI exhaust is $700, headers another $700. This is omitting all the other options.

    Let's say you spend $1200 on dual exhaust and a new carb, all-in. What are you going to get? 13 and 16 mpg? I don't think you're realistically going to be getting 15 and 20. Half city driving and half highway driving means you'd save $0.03 per mile. That works out to 50,000 miles before you break even if gas is $2.50 per gallon. At $3 it works out to 40,000 miles.

    How many years to get that mileage? And are you really going to engineer a 15% improvement in mileage that easily? I'd guess it's going to be a lot less in the real world.

    Now if you want 3.23s and headers and duals, and a new carb because it will sound cool and give just that extra pleasure in driving, I'm all for it. It makes complete sense.
     
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  11. Mopar Madness

    Mopar Madness New Member

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    Don't know much about 400s with lean burn. But Baja post reasonable.
     
  12. BeatersRus

    BeatersRus Active Member

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    thats exactly what i meant too.
    heck,the rear gear and duals alone will prolly be close to 1K.
    thats not even talking tuneup or timing chain nor water pump nor gaskets.

    And.
    once you yank the motor and trans,
    esp a 440 and start buying parts and then machine work,it gets to 5k Quick.


    Then.
    they need the rest of the upgrades,to go With that now awesome 440 but hey they went Broke on the budget.
    and now they are out of money and whammo next thing you know that shiny 440 is up for sale.
    happens all the time.

    this is why id rather have a 9-1 comp 383 than a 8-1 comp 440.
    and i have a healthy decent 440 too,but,its a smogger.
    just a few thoughts....
     
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  13. Henrius

    Henrius Member

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    Thanks for the good info. But my 1965 Fury has a 9.5:1 compression ratio. I always drove it on modern regular until I went to non-ethanol fuel of about 90 Octane. Also I upped the CR in my Pinto to the same and drive it on regular non-ethanol and don't have a problem with knock.
     
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  14. Henrius

    Henrius Member

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    Thanks I guess I am a tinkerer who always want to create more efficient machines.

    Thanks for the tip about torque convertors. I don't know much about transmissions and did not know there was a choice in stall torque. A transmission with less slip would be just as good as a transmission with a lockup 3rd gear? Is there any drivability penalty in a less slippery torque convertor?

    I am beginning to hate carbs, too, and was wondering about the practicality of going fuel injection- although it would take the car far away from original. FI kits are car-specific, or just engine specific? I know nothing about them.

    I don't quite get what you are saying about headers. You are saying it is better to maintain heat with manifolds- or a liability?
     
  15. Henrius

    Henrius Member

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    Thanks Kevin!

    The electronic ignition was an upgrade I made long ago. What about an MSD unit? Would that be worthwhile?

    A thermoquad would only help top-end performance, wouldn't it? And then I would have to find a new intake manifold for it. I guess the Thermoquad was the factory option for that model year, since it appears in the Service Manual after the Holly 2210 I have on the car now.
     
  16. Polara_500

    Polara_500 Well-Known Member

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    A thermoquad can actually help with mileage also due to the small primaries. They can be a bear to get right but do well if/when you do.
     
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  17. Turboomni

    Turboomni Senior Member

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    May I ask what your rear ratio is? And good to hear from you !
     
  18. Henrius

    Henrius Member

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    Know as little about gear ratios as I do about transmissions. I thought the differential was bad and swapped it for another from a junkyard Newport. Is the ratio printed on the differential? If not, how to tell without disasembly and counting the gears?
     
  19. Henrius

    Henrius Member

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    I hear you. My 383 in the 1965 Fury has always run so much smoother than my 400. And about 2mpg better gas mileage as well.
     
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  20. Turboomni

    Turboomni Senior Member

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    Count how many times the drive shaft turns to one full rotation of the tire.
     
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