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Engine basics => Engine set up tips => Topic started by: Vince Mankowski on March 08, 2013, 11:24:56 AM
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Have two of these & each one seems to have a different bore of the venturi (sprinkler). If anyone has one & can use number drills as pin gages, please tell me what the diameter of your Mark II venturi inlet.
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Hi Vince,
Which Webra are you talking about. There were at least seven or eight different models / sizes to my limited knowledge. Personally I wouldn't worry too much about the different diameter venturis. They all ran very well indeed, with perhaps the exception of some of the 0.8cc Picalos. At least I had an iffy one!
Regards,
Andrew.
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Not a 'Piccolo' (0.8ccm), Not a 'Record' (1.5ccm), Not a 'Winner' (2.5ccm), Not a 'Bully' (3.5ccm)
it is a "Mach II" ..... a 2.5ccm diesel from the 1960's, back then it was "the" Team Race 'motoren' into the mid 1970's.
I have two of these, one has a venturi bore of (approx.) 2.4mm (or .098"), the second has a venturi bore of 3.16mm (or .129").
This seems to be quite a big difference, especially for a diesel. This difference appears far more then the difference between "stunt" and "racing"
It seems more like someone boreing out (drilling) until the motor becomes unable to to get a decent needle setting with proper compression settings. Or someone making a super-small intake to achieve "higher mileage" (read run to hot)
I just want to know which one was correct.
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Vince
I have an engine test of the Mach II at http://sceptreflight.net/Model%20Engine%20Tests/Index%20Diesels.html where it says that early engines had a 4mm venturi then later reduced to 3.5mm so I guess it's possible that they may have been reduced even further.