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Intake Castings / SU Carb rebuild

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  • Intake Castings / SU Carb rebuild

    I am sending my (4 Bolt) SU's, and related pieces (Intake Castings & Balance Tube) off to Z Therapy for rebuild. My Zed was production date (Sept 71). Although the intake castings have plumbing for circulating coolant they have no provision for circulating that water thru the carbs (as later models did). The related tubing, and hoses all look like clutter. This could be opportunity to clean it up?

    I understand reason for warming the charge was intended for winter conditions. In addition (it seems) my assembly is seemingly only half the job intended as only the intake castings are warmed. I have a choice now to remove all that plumbing or not. Z Therapy will do the refresh either way.

    I would appreciate any feedback / opinions / experiencess which might help me to decide, Heat or No Heat to intake charge?

  • #2
    Ran the 510 for years with two 40dcoe's and no manifold or carb heat of any kind. Never had a problem. Even daily drove one year round in that configuration without any issues. None of my performance manifolds have any heating.

    I have early 510 heads that don't have any provision for coolant flow through the manifold and no coolant passage in the manifold anyway. There was a manually operated flapper in the air cleaner inlet to draw heated air from the manifold heat stove for winter use. To prevent carb freezing.

    Later heads and manifolds had water passages and the air cleaner housing had vacuum operated flappers controlled by a thermostatic valve for carb preheat. A coolant pipe ran from the manifold outlet to the intake for the waterpump. When the thermostat is closed coolant can still circulate through the block, the manifold and back to the waterpump warming the intake charge. Warming the intake helps a cold engine atomize the fuel charge for better driveablity. Warming the intake air, or carb, prevents freezing in the carb. There may also be emission control benefits also but I'm not 100% sure of that.

    Here's an interesting read on intake manifolds.
    67.5 Roadster project
    71 510 wagon
    74 CB360T
    2006 Nissan, retired parts getter. Sold and out of retirement.
    2013 Toyota Corolla
    Formerly 510er
    It's amazing how one tiny capacitor can wreak so much havoc.


    • #3
      Thanks Howie! appreciate your take on all . . . your point on the emissions may have stuck the nail head since originally the zee came with more pumps/ hoses/ valves than a Maytag . . . those are all gone now so too may be the additional plumbing. Got a month before I send off the pieces so a bit of thinki time . . .
      Intersting artcle on intake maniflolds