Preheat pipe to airfilter/carb

Discussion in 'Mech Tech' started by volkswombat, Mar 28, 2017.

  1. I'm sure I saw this in a thread somewhere but now I can't find it.

    As part of a service I want to check the preheat pipe (stove pipe to air box for carb) is working right, the vacuum operated flap in the airbox snout.

    How do I test the flap is working right?
     
  2. when you find out let me know as my engine never had one but I hope to get them for the new pretty much stock engine.........
     
  3. With your engine cold, shine a torch up your snout. You should see the flap shut. Go for a good drive, park, dash round the back and look up your snout again. Flap should be open.

    Or...suck on the vacuum line and use a hot air gun.
     
    foe, scrooge95 and volkswombat like this.
  4. I never had the stove pipe fitted before but did stick a tube over the relevant hole and up to air box,
     
  5. Is that it !
    I seem to remember quite a lengthy text about it!
     
  6. That's it. All you've really got to do is check that the thermostat in the airbox opens properly (60*?). This is assuming that the flap diaphragm and connecting rod are working properly - may be worth carefully (easy to break clips) unclipping the snout to check whether the rod has rotted through.
     
    Last edited: Mar 28, 2017

  7. so I should look up the air filter snout and it should be blocked so the air is going to come from the pipe attached to the stove pipe that's aimed at no2 cylinder.
    I have seen some tinware that goes to no2 cylinder that has a hole in it for the stove pipe, is that right because my tinware does not have the hole.
    I take it when it gets warm enough and if its working correctly I should be able to see past the flap up into the air filter box.
    this is in the future for me, I don't have any vacuum pipes coming off the carb going to air filter box just the tank breathers.
    cheers
     
  8. That's how I remember it. There should be a third hole in the tinware for the stovepipe (other two for the hoses/pods for the heat exchangers). The flap valve is powered either from a small take-off from the manifold, or a vac line from the rear of the Solex.

    Worth having working properly, as it does prevent manifold chilling in my experience. Need to make sure it opens again when the engine's warmed up, as the motor doesn't like breathing hot air.
     

  9. yes 3 holes in the tinware but the other end of the stovepipe near no2 should there be a hole in the funny angled shaped bit of tin, sorry I don't have a pic of the tin but 1 on either side closing off the rear of the cylinders.. I'm off to find them on heritage, may take a while...
     
  10. The stovepipe goes under the angley bit, through the gap.

    a stovepipe 2 4s.jpg
     
  11. cheers for that pic, do you have one of the other end of that stovepipe near to the cylinders:thumbsup:
     
  12. I do, Sir.

    a stovepipe 1 4s .jpg

    <edit> Oops, not the other end. It just pokes in the general direction of the thermostat. The other end has a cutout in it.
     
  13. Think i know the bit of tin you mean, the vertically positioned peice, 1 each side.
    If so then no the stove pipe sits to the side of it. The pipe end is angled to go round it.
    It is a very awkward fit, but some guidance from snotster helped. Had to bend the tabs to make them fit the tinware screws you can see in that first pic ^
    Lots of tab bending, try to fit, tab bend ,try to fit etc
     
    wendygun likes this.
  14. My snout flap is fully operational, thank-you.
     
    paradox and snotty like this.
  15. Did you look up your snout hole?
     
  16. bluerustybucket

    bluerustybucket Supporter

  17. The other two bits should be fitted already, they go in front of the heads as you look at engine.
    If they're not fitted you've got bigger problems ;)
     
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  18. bluerustybucket

    bluerustybucket Supporter

    i dont think they are... but could be wrong, whats the bigger problem ? :eek:
     
  19. bluerustybucket

    bluerustybucket Supporter

    just had a look on the t'internet and still available from the usual suppliers, but don't think mine are fitted
     
  20. Trying to remember, think you'll need to look for them from underneath the big tin, they hang down under the over cylinder tins on each side, so either side of pulley wheel. I think! Someone better than me may be able to explain better.

    I'm assuming your engine is in the van and running? Id be surprised if they're not there!
     
    bluerustybucket likes this.

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