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Carbie too close to firewall?

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Old 11-27-2006, 05:21 AM
  #1
Jakmun
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Default Carbie too close to firewall?

Hello Mike
the carbie intake on my zdz80rv is just under 1/2 inch in front of the firewall (see photo). I am wondering if it is too close, and not able to suck enough air at high throttle settings.

I am getting 5800rpm with Bolly 26X10 wood, CHT 210 deg F, 40:1 synthetic with 95 octane, it has had 5.5 gallons since new. it transitions well to 3/4 throttle, then seems to "sag" from there to full throttle (rpm briefly increases then drops back 1/2 a second later). i am 1/4 turn out from the lean point in the hi needle. (which is about 1/8 turn in from the "rich" point), but it does this at all hi needle settings between the lean and rich point. sensor is at 6mm before tdc. (actual spark is occurring at 2mm before tdc).

i'd appreciate your thoughts.
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Old 11-27-2006, 11:15 AM
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Mike Dooley/RCS
 
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Default RE: Carbie too close to firewall?

Yes, the carb is far too close. Get a 1-1/2" hole saw and bore through the firewall. Be sure there is no debris that could be ingested.
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Old 11-27-2006, 12:15 PM
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RCDennis
 
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Default RE: Carbie too close to firewall?

Mike,
This brings up a question. Is there a formula that is used to determine the distance the carburetor opening should be from the firewall? I understand that by drilling the hole size recommended that this increases the area around the carburetor intake. But at what point does this become necessary? Thanks Mike.

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