WDO Carburetor Jet Changes?

hudsonguy
hudsonguy Senior Contributor
edited November -1 in HUDSON
Generally speaking, should a person use larger or smaller jets with today's gasoline?



I'm in the process of tweaking my '49 262 motor (with WDO carb.), and I know I've read tidbits of advice relating to setting up an older carburetor to run today's gasoline. I just can't seem to find any of those threads at the moment.



I've got three different WDO carbs. (all are model no. 647SA) They all had different size metering rods, which have a significant impact on the way the car runs. I've realized the 'straighness' of these metering rods is of utmost importance, too. There are also a couple different size jets between the three. According to the book there should only be one jet (.086" dia., I think)



Also, should my float setting remain the same as the book spec.? (3/16")



Thanks for the help.



Doug

Comments

  • Geoff
    Geoff Senior Contributor
    You will need to lower the float level setting to suit modern gas, as it has a lower specific gravity than gas in the fifties, therefore the float sits lower in the gas than original. The float level adjustment is of course a static setting relating the top of the float with the bowl cover, with everything upside down. This is fine if the specs of the gas remain the same, which of course they haven't. Lower the float level 1/8" and see how you get on.

    Geoff.
  • dwardo99
    dwardo99 Expert Adviser
    OTOH, if they go forward with adulterating the gas with more ethanol, it will run leaner than before. I'd wait and see what bastardized gas we'll get next.
  • hudsonguy
    hudsonguy Senior Contributor
    Thanks for the help. I'll try a lower float setting.



    I guess the main tuning problem I'm having is regarding the metering rods and their jets. The high speed circuitry that this controls seems to 'fluctuate'. I can feel the car surging, and kind of struggling a little when under load, and I'm pretty sure my metering rods are jumping up and down. It seems to be running lean. So for whatever reason, the rods aren't settling in to their proper position, which is controlled by engine vacuum, and the rate of the little spring that lifts the piston assembly.
  • hudsonguy
    hudsonguy Senior Contributor
    I just spoke with John at the Carburetor Shop, in Missouri. He seems to be pretty knowledgeable on all things 'carb'. His advice was as follows;



    Since I'm burning 'corn gas' (10% ethanol) here in Wisconsin, his advice was to RAISE the float level by 1/16", and try to get a richer mixture for the first 1000 miles on my rebuilt engine. He said to use standard metering rods (rather than 1st leaner, 2nd leaner, etc. ) and standard jets, so we know where we're starting from. After I've got some miles on the engine, he suggested that we then try to dial it down a little leaner, by possibly remaking new metering rods, if necessary. He actually has the metering rod lathe that came from Carter, and can make new rods for $140/pair. Kind of pricey, but he said it takes 4 hours to make them, so that's understandable.



    I'm also buying a rebuild kit from him, which comes with a new piston spring, and new jets. He also suggested for any cross country driving I might do, that I have two carbs with me. One for ethanol, and one for 'regular' gasoline. I am planning another trip to California in August, so I may just do that as well.



    For anyone interested, I can post my results as I go along this path.



    Hudsonly,

    Doug
  • Geoff
    Geoff Senior Contributor
    Okay, somebody has moved the goal posts and changed the rules halfway through the game!!! We don't have this half-baked biogas out here in the colonies. Obviously the car is running too lean, so lowering the float level is going to exacerbate the problem. Either fit a thinner metering needle, or raise the float level, or both. Murphys Law, corollary # 71, "If you fiddle with a thing long enough, it will ultimately break".

    Geoff.
  • dwardo99
    dwardo99 Expert Adviser
    Dwardo's Law: "If it ain't broke, fix it 'til it is".
  • hudsonguy
    hudsonguy Senior Contributor
    "If we didn't have something to fix"......well I won't even go there! Once a garage rat, always a garage rat.



    All I know is that right now my car IS broke, and I'm tryin' to fix it! Half-baked biogas is right, Geoff! It's only going to get worse around here. Right now typical 'pump gas' in Wisconsin is 10% ethanol, with a change to 15% looming on the horizon. Of course, then there's the dreaded 85% stuff that's also in the works!



    That reminds me. Does anyone make or sell Neoprene diaphragms for the AC combination fuel pumps? As far as I know the rubber one that is standard is only good for about 10% ethanol, so I'll probably be needing one sooner or later.



    It was definitely running way too lean, surging, etc., and after simply raising the float level 1/16" (meaning a 1/8" measurement on the inverted float to cover dimension, which is spec'd at 3/16" in the manual), it runs WAY better. It's still got a ways to go, though, so I'm going to try a richer (smaller) set of metering rods that I've got, and hopefully sneak up on the problem.
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