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Subject: Vacuum?

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Rusty 2N    Posted 05-24-2018 at 21:07:34 [URL] [DELETE]        [Reply] [No Email]  
  • Vacuum?
  • What is a normal vacuum reading?

    Bruce (VA)    Posted 05-24-2018 at 21:19:01 [URL] [DELETE]        [Reply] [Email]  
  • Re: Vacuum?
  • On a model A Ford, also a flathead 4 cylinder engine, 18 is optimal.

    Rusty 2N    Posted 05-24-2018 at 23:45:28 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Vacuum?
  • Thank you Bruce. I was thinking 20. So still sucking air. Bouncing around 15 and runs rough.
    Thinking out loud here, idles at 450-500 rpm till it runs out of gas. Timing set at 4 btdc. Starts in less than one crank. Good compression tests. Plugs passed the blue gap flash test.
    I am comfortable with dist and 241 carb now.
    Intake manifold, maybe valve?? Tomorrow is another day! Rusty

    Tony C    Posted 05-25-2018 at 16:34:33 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Vacuum?
  • If the needle jumps quickly between fourteen or so and seventeen then steadies on acceleration could be worn valve guides IIRC. Are you diagnosing the sudden onset, slow development or a machine you just got?

    Rusty 2N    Posted 05-25-2018 at 21:54:57 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Vacuum?
  • I got this tractor a couple years back. Never been able to get it to idle or run smooth. Life didn't let me do much more than keep it running good enough to keep the snow off driveway and spray weeds maybe. Life changed a bit and I knew the dist needed a serious looking at. That led to a dist rebuild. Seen that coming. Does perform better after that. But still rough but better up and down the throttle. Got lucky and got the plug out of vacuum port and hooked up a vacuum tester. Needle bounces all over the place between 10 -15 hg. Have 2 carbs I been swapping back and forth with and decided to make the 241 the keeper. Did that. Posted on Bruces post.
    Wireing harnes and all the electrical is only a couple years old. Purchased from Just 8n's so all good there.
    I do have a close to new manifold and gaskets so considering swapping. The one on it now looks to be original. Same orange paint as the rest of the tractor. Was a city parks dept rig for it's first career. Still has the number 24 on the dog legs!
    Sister showed up and I went to town for some food and parts and not wanting to do much more than recuperate from that insane endeavour!!! Boy, was Walmart in all it's glory today!!!
    Well thats the story so far tonight. I will eventually get this girl going. Rusty

    Bruce (VA)    Posted 05-25-2018 at 06:54:42 [URL] [DELETE]        [Reply] [Email]  
  • Re: Vacuum?
  • Front or side distributor?

    Get out the hand-held propane tank and spray it around the carb and manifold. If the rpm's increase, you found the leak.

    Carb is probably sucking air around the throttle shaft.

    Rusty 2N    Posted 05-25-2018 at 08:37:21 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Vacuum?
  • Did that. Didn't get a change in running. Found one after shutting engine off and was wondering why that gasket between body halves was wet again when I watched a bubble form and pop at that corner screw. Took a couple hours to go through this 241 and seems to have helped considerably. Did the torch and wd 40 thing again but got late and I got hungry. Should be able to get back to it later today. Rusty

    Tony C    Posted 05-24-2018 at 23:11:29 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Vacuum?
  • Pretty much the number for most gas engines regardless of configuration. 17-18 Needle steady, Drop to 5-6 on snap accel. 21 on snap decel. Numbers not set in stone, some engines in good shape will run a little lower or higher. I've seen a couple at 21.

    I shoot for 17-18 when adjusting the idle mixture and initial idle setting.

    Needle movements can be used for diagnosis. Low, Hunting fast,drifting lazily etc.

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