WA-1 carbs and vacuum

dougson
dougson Senior Contributor
edited November -1 in HUDSON
Do the Carter WA-1 carbs on the twin-H setup produce much vacuum? I have the vacuum advance hooked to the front carb and there is practically no diference with the advance plumbed in or removed, maybe a few degrees. A have two vacuum gauges set up and I'm getting 20" at idle whether the advance is connected or not. Does the advance come off ported vacuum? If true, there must be a reason for this because manifold vacuum would produce a lot more vacuum (it seems) at idle.

Comments

  • Park_W
    Park_W Senior Contributor
    Vacuum for the advance is indeed off a port that's a little above the throttle plate when in idle ... you have to be a little off idle to get vacuum to the distributor. They didn't want any vac advance at idle. Also note that the Hudson distributors don't provide nearly the amount of vacuum advance that's seen on other cars. You can look at the spec's and see that the vac advance is very modest, so you're not going to see ten degrees or anything close.
  • [Deleted User]
    [Deleted User]
    Vacuum advance does not work at idle, only when you increase the engine. Timing set at idle, long mark on flywheel. Disconnect the vacuum line and race engine and mark should raise about 2 inches. Connect vacuum line and race engine and mark should go clear to the top of the opening in the motor plate. Total advance with spark disconnected is 9 degrees and with it hooked up vacuum advance goes 4 more degrees for a total of13 degrees. If vacuum does not increase timing, check the vacuum advance unit to see if it can hold vacuum, if not must be replaced. Walt.
  • Sarah Young
    Sarah Young Senior Contributor
    Can you explain what the purpose of the screw/rod in the pictures are? (Pointed at with screwdriver.)



  • [Deleted User]
    [Deleted User]
    If you mean the shinning round head with the screw driver slot, that has a gasket on it, and must be tight, as the idle jet is under it. Walt.
  • GrimGreaser
    GrimGreaser Senior Contributor
    Does it 'fit' into a matching jet in the bowl? Kinda looks like the needle of an adjustable main jet.
  • [Deleted User]
    [Deleted User]
    It's a hollow tube the screws into the main body with the correct size hole for the car it's on. All WA-1's take a different size hole. They have numbers stamped on the top, like 53-54 Jets take number 11-169s, 50 to 54 Wasp and Pacemaker take number 11-165s. What is the carter carb number you took the picture of and what engine does it go on? Walt.
  • GrimGreaser
    GrimGreaser Senior Contributor
    edited September 2011
    I don't think she's pointing at the idle jet. I just rebuilt my Twin H WA-1's, I don't recall whats pointed out as being on mine. I'm not familiar with any other WA-1 configurations however.

    It looks like it sits over the pump inlet hole, between the idle jet well and the pump well. With it being pointed, it kinda looks like the needle of an adustable jet set-up like on Strombergs, ect.
  • Geoff
    Geoff Senior Contributor
    This is an adjustable jet that is used on replacement Carter WA1 carburettors for Universal use. Instead of specific metering rods it uses an adjustable needle. If your car is running too lean you wind it up, and too rich, wind it down. You can enable or disable the vacuum piston, by unhooking the torsion spring, whichever makes the car go better.
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