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Speed,Combat,Scale,Racing => Speed Talk => Topic started by: Tim Stone on June 20, 2019, 05:59:59 AM
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Maybe someone can help save me some time. What venturi size are you using on NovaRossi .21 on crankcase pressure?
And diameter of pressure tap? Thanks I could not find much when I searched.
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Hi Tim
The motor I used many years ago, came from Gillot with the Venturi the same size as the crank bore, I would at least start there.
Les
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Hi Tim
The motor I used many years ago, came from Gillot with the Venturi the same size as the crank bore, I would at least start there.
Les
Thanks Les it is hard to argue with Tim Gillotts' methods.
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Pressure tap can be 4-40 fox or K&B unit. Don't over tighten it or it will snap off. Use loctite and barely snug it. I've actually gone to a 6-32 nipple but with a restrictor in the line that has a #69 drill hole and is also a check valve. Side note the old KK check valves for 1/2a aren't big enough. Venturi? what venturi. Is it for upright cowled in or profile? Beyond a certain size there is no gain but you can go .440" if you have good height and shape to prevent the prop blast from blowing the fuel out. You're also dealing with centrifugal force slinging the fuel out on a profile. On my proto I have a .400" that's 3/8" above the crankcase. The choke is down by the spraybar and it has about 10-12 degree taper. I use 7075-T6 because the sections get pretty thin. Enough secrets for now lol.
Motorman 8)
Thanks I appreciate it.
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Time just looking at some old notes and see where one of the fastest 21 SS had a 390 venture in it
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Time just looking at some old notes and see where one of the fastest 21 SS had a 390 venture in it
Thanks Bob I appreciate it.