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Author Topic: port timing on VF46  (Read 810 times)

Offline Gordon Tarbell

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port timing on VF46
« on: June 30, 2011, 08:49:07 PM »
Just got two pipes from Randy Smith (he said he was leaving for the NATS so I figure I would post here instead of bothering him) one for my VF46(51 size ultra quiet pipe) and one for the Mvvs 49 (ultra torque) Any one know what the port timing is on these two engines so I can use the correct reference collum on the pipe chart he sent. Three of the collums have OS listed at the top 140 degree, 145 degree, and 150degree.others listed are 130degress ,135,133, and 155. Making like a chicken and putting my best Mark1 eyeball on it I want to say the OS 46 VF is 145degrees and the Mvvs is 130 If anyone can confirm the exact numbers let me know otherwise I will dig out the ole degree wheel and actually have to measure it this weekend.  He didn't say what RPM to shoot for  for starting lenght on pipe. I thought I might set the needle valve to where it just is starting to switch back and forth into a two stroke mode.
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Gordon Tarbell AMA 15019

Offline RandySmith

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Re: port timing on VF46
« Reply #1 on: June 30, 2011, 09:17:02 PM »
Quote from: gordon tarbell on June 30, 2011, 08:49:07 PM
Just got two pipes from Randy Smith (he said he was leaving for the NATS so I figure I would post here instead of bothering him) one for my VF46(51 size ultra quiet pipe) and one for the Mvvs 49 (ultra torque) Any one know what the port timing is on these two engines so I can use the correct reference collum on the pipe chart he sent. Three of the collums have OS listed at the top 140 degree, 145 degree, and 150degree.others listed are 130degress ,135,133, and 155. Making like a chicken and putting my best Mark1 eyeball on it I want to say the OS 46 VF is 145degrees and the Mvvs is 130 If anyone can confirm the exact numbers let me know otherwise I will dig out the ole degree wheel and actually have to measure it this weekend.  He didn't say what RPM to shoot for  for starting lenght on pipe. I thought I might set the needle valve to where it just is starting to switch back and forth into a two stroke mode.

Hi Gordon

Use the chart I sent and use the 145 for the OS and use the 135 or 140 for the MVVS, set the needle on both for the fastes 4 cycle the motor will run in or just starting to cackle back and forth into a 2 cycle. Then launch there, The motors will unload and go into a solid 4 cycle. Use about a 4.2 to 4.6 pitch prop for both engines. Then adjust lap speed to suit by pitch. Adjust stronger or weaker break by nitro
We used a Bolly 12.25 x 4.25 2 blade, and Bolly 12 x 4.25 3 blade for both of these motors
You will be in the 17.5 to 18 inch range for both engines
Much of this will depend on other factors such as airplane size, weight, drag, site location etc

Randy

Randy
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Offline Brett Buck

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Re: port timing on VF46
« Reply #2 on: July 01, 2011, 06:08:58 PM »

   All the VFs I have measured were in the range of 143 to 146. 145 ought to be close enough to start with.

     Brett
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Offline Gordon Tarbell

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Re: port timing on VF46
« Reply #3 on: July 01, 2011, 08:17:23 PM »
Thanks guys . Randy I did not want to bother you while you were getting ready to go to the Nats.  Thanks again. 
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Gordon Tarbell AMA 15019

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