Gas Guzzler question

[Deleted User]
[Deleted User]
edited November -1 in HUDSON
My rebuilt 54 308 now has about 425 miles on it. It has the Twin H setup and is running a Clifford duel exhaust header. The engine runs great, is properly timed, idles smoothly, and the exhaust tip has a nice dark brown color, i.e. does not appear to be running rich. The problem is that when it passes a gas station it pulls to the right. I am getting about 8 mpg. YUK

Given the mileage om the engine, is the 8 mpg to be expected? How many miles before engine is broken in? About half the mileage is at about 50 mph or better but nothing over 60.

Thanks,
Doug

Comments

  • RL Chilton
    RL Chilton Administrator, Member
    The Twin-H notoriously gets pretty bad mileage, but nowhere near 8!:woohoo:

    Expected is 13-16, fairly easily, hwy speeds. I always expect to get about 16 minimum when properly tuned, sometimes, even a little more.

    Break-in is typically at 500 miles for most new engines, Hudson not excluded. Regardless, the mileage is not going to magically get better gas mileage after break-in (maybe just a little, but not like 5-7mpg better). Besides, for all practical purposes, you are all ready there.

    Problem lies elsewhere, my best guess. Timing, over-pressurized, wrong jets in carburetor, leaks, . . . parking brake is on, brakes are dragging, wheel bearings too tight, wrong kind of gas or a combination of any of the above and more can lead to poor gas mileage.
  • [Deleted User]
    [Deleted User]
    edited August 2011
    RL, thanks for your response. Need some clarification on your comments. When you say over-pressurized what are you referring to? Exhaust pressure? I am running the duel exhaust header into one pipe which was supposed to be large enough to accomodate the duel exhaust header. "Wrong kind of gas". I am using regular, 87 octane with that damn Ethanol.

    Spark plugs are not fouled, all hoses are new, and timing is right on the money. I have the valves set at 12 and 14 as opposed to the stock 10 and 12. This to adjust for hotter burning of today's gas per Walt Mordenti.

    Dragging brakes. I did notice that after a drive yesterday with some stop and go, that the hupcaps were fairly warm. I would not call them hot however as I could keep my hands on them.

    The only other problem I am having is that the engine is running hot. Needle got over to about 3/4 toward H by the time I got home. Could this be an mpg issue? I have ordered a 160 degree thermostat.

    Thanks, Doug
  • Terraplane33
    Terraplane33 Expert Adviser
    I had once a similar mileage with a 2.8 V6 Ford engine, it appeared that the fuel pump was leaking into the engine oil. I could smell gas but no leakage, oil level was OK when cold (gas evaporated by engine heat I guess) but far too high when hot.
    Don't know if this may help...
  • [Deleted User]
    [Deleted User]
    Does your starter turn the engine over OK when it is hot? If not could be the piston clearance is too tight..Did you bore it with new pistons?
  • Marconi
    Marconi Senior Contributor
    lso, what do you have for a transmission? Std, auto, O.D.? and what ratio is your rear axle?
  • Jon B
    Jon B Administrator
    Just an aside: on what do you base your mileage calculations? Have you verified your odometer by comparing it to the green mileage indicators on the nearest Interstate highway? (It's a long shot I know, but maybe you're getting better gasoline mileage than you thought!)
  • RL Chilton
    RL Chilton Administrator, Member
    edited August 2011
    dougc_portland wrote:
    RL, thanks for your response. Need some clarification on your comments. When you say over-pressurized what are you referring to? Exhaust pressure? I am running the duel exhaust header into one pipe which was supposed to be large enough to accomodate the duel exhaust header. "Wrong kind of gas". I am using regular, 87 octane with that damn Ethanol.

    Spark plugs are not fouled, all hoses are new, and timing is right on the money. I have the valves set at 12 and 14 as opposed to the stock 10 and 12. This to adjust for hotter burning of today's gas per Walt Mordenti.

    Dragging brakes. I did notice that after a drive yesterday with some stop and go, that the hupcaps were fairly warm. I would not call them hot however as I could keep my hands on them.

    The only other problem I am having is that the engine is running hot. Needle got over to about 3/4 toward H by the time I got home. Could this be an mpg issue? I have ordered a 160 degree thermostat.

    Thanks, Doug

    Doug-

    You answered your own question with the exhaust . . . should be fine.

    Today's gas: might want to try running the 89, or middle grade gas. I think even stock Hudson's tend to run a little better, and as yours is a little hotter (meaning power), it might benefit you, as well.

    Valves should be good, Walt's right.

    As far as the dragging brakes go and the engine temp:
    You don't have an over-heating problem, providing your sending unit is correct.
    On the gauge, straight up and down is 160. Lines represent 20-degree increments. 3/4 mark is 180, "H"-mark is 200. Hudson engines running in the 21st century (with our modern gas) should run a little hotter than the stock 160. Should be somewhere in the 165-185 range. If your needle gets up to "H", shut it down. Bouncing between 1/2 to 3/4 range is normal.
    Word of advice: Buy a heat gun that has the laser in it. When pointed at an object, it gives a very accurate temp reading. Can be pointed at wheel bearings, engine blocks, anything, really. Easy way to check how much heat is actually on an object. Mechanics use them, cost is usually around $120, but well worth it. You should absolutely be running a 160 thermostat with a 7 lb. cap.

    Jon brought up a great point, Hudson speedometer's and odometers read notoriously slow. If you are judging gas mileage upon your dash readings, it might not be accurate.

    "Over-jetted", which I brought up earlier refers to the jet size inside your carbs. Larger jets will dump more fuel. Might want to find out if you have the proper sizes installed. Just a thought.

    Really, there's so many possibilities, you just have to check them one at a time. BUT, there is absolutely no reason not to be getting in the 15-16 range, regardless of transmission. Rear end ratio will make a big difference here. Generally, stock gears are too low for modern highway speeds.

    Hope some of this helps-

    Russell
  • [Deleted User]
    [Deleted User]
    A couple of thoughts on your mileage. Check to make sure your chokes open all the way at operating temp. May be you will need to remove the manifold and pop the freeze plugs and clean--sandblast the passages for heat transfer. Next is the WA-1 carbs. The main jet in most of WA-1 carbs are drilled at .1015 including the 232,262,308 & jet motors. The flow is adjusted by the metering rod which are numbered for that particular application and must be set properly. Look at your plugs and if they are wet and black, and if they are, that is probably your problem. You should be getting a min. 16 MPG. This year I built a 7X relica motor for Jack Howe in Auburn, Ill. and he is getting 16. Another rebuild using my 402 lift & 276 duration cam using my modified WA-1s with larger weber venturis claims 20-22 mpg city and hwy. Hard telling what you have until you check the numbers. Currently I am rebuilding a carb for a guy in McHenry, Ill. He got a carb from Al Saffrahn that came off of a Jet. After inspection, the carb was orginally a Super Wasp Twin H carb. Two changes I need to make, one-install the correct metering rod and drill out the squirter jet .009 to the jet spec. of .031.

    Randy
  • [Deleted User]
    [Deleted User]
    Thanks to all who responded. I am sending the carbs down to Walt Mordenti for the proper adjustments. I don't have the tools or the knowledge to set them up.

    Thanks again, Doug
  • Matt1950
    Matt1950 Senior Contributor
    edited August 2011
    One thing to check on all engines that use centrifical/mechanical advance and a vacuum advance is to confirm that both are functioning properly. Since timing affects engine temps.

    EXAMPLE: Some Stepdowns had 4 degree and 8.5 degree vacuum advances in 1948 and 1949. With about 8-10 degrees of centrifical advance for a 6 cylinder.

    Vacuum Advance
    The vacuum diaphram should not leak and should be verified that it is funtioning to the tune-up specs in the service manual. The vacuum line (if not mistaken) is below the throttle plates so it is using intake manifold vacuum at Idle (approx 10-12" of vacuum). This applies 4 to 8.5 degrees of advance from base timing at idle. As you press the throttle the vacuum drops down to zero and the mechanical advance takes over. (Vacuum advances using idle/manifold vacuum typically provides improved idle performace for your vehicle)

    So if this vacuum unit is bad you will be 4 to 8.5 degrees retarded in your base timing curve.
    Retarded timing can cause higher engine temps especially at cruising speeds so the vacuum advance typically provides advance at idle and light load small throttle openings.

    Mechanical Advance
    In the Electrical System section of the Mechanical Procedure Manual you can find your distributors specs. With the vacuum advance disconnected you can confirm at each given/listed rpm if your distributer is advancing the timing according to the spec/rpm. replacing springs and cleaning the weights and pivits can put your distrubutor back to original specs.

    So if you originally set your timing to TDC or UDC (0 degrees)at idle (~650 rpm) by 1200-2000 rpm you should be at full mechanical advance 8-10 degrees. With a dial type timing light you can check to see you are hitting your full advance.
    NOTE: The Hudson service manual suggests that you can advance your timing until you here "pinging" (spark knock) while driving at full throttle and retard it by one degree or one timing line mark untill the noise goes away. To do this you need a fully fuctioning distributor.

    I hope this info helps.

    You retard timing on a Hudson by rotating the distributor clockwise.
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