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mvvs 40 old pylon engine

Old 07-16-2007, 02:51 AM
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Default mvvs 40 old pylon engine

i have bought a second hand pylon engine model no 3070 with a pipe pt no 3247 and what i will describe as a grooved manifold. i am grafting this into a mig17 ish plane and was wondering what props suit this engine and pipe. also do i need to trim the grooved header pipe. looking through the old posts a prop like 8x8 or 9x7 looks posible but will thses allow the engine to use the pipe to its maximum. i have no documentation on this engine
Old 07-16-2007, 07:02 AM
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Default RE: mvvs 40 old pylon engine

The pipe is tuned to the engine. Next you must tune the prop and fuel to the engine-pipe setup.
9x7 will certainly be too large to get on the pipe, which seems to be tuned for ~24000 rpm. At least a quickie I tested will not.
I removed the thicker coupling from the pipe, and used the standard silicone coupler method combined with a rear exhaust stack. That allowed me to tune for lower rpm.
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Old 07-18-2007, 08:11 AM
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Default RE: mvvs 40 old pylon engine

BearSa,


I must add that the #3070F/R GRFT/GRRT engines are the NEWER pylon racing engines that MVVS had to offer - not the old ones.

The old version was the #3065 GRRT, which was essentially the basic #3066 .40/6.5 cc engine, with a closed front crankcase and a rear-intake...


The #3070 versions were discontinued as well, because of very low sales - not because of any performance deficiency.

I believe your engine has a needle bearing con-rod - unique even in specialty engines like this one.
Old 07-19-2007, 08:37 AM
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Default RE: mvvs 40 old pylon engine

it also has a carb with a 7mm dia throat and a spring for adjusting the needle would this engine benefit from a larger carb it flick starts real easy
pe reivers,
have you any measurement of how much longer the manifold needs to be for lower rev operation (to save me some time)
Old 07-20-2007, 05:35 AM
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Default RE: mvvs 40 old pylon engine

Bear,


Can you post some photos?

Some of what you wrote does not agree with the items available for this engine...


The dedicated #3226 carburettor has a huge choke diameter - not a puny 7 mm one.
Old 07-20-2007, 02:17 PM
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Default RE: mvvs 40 old pylon engine

No, I can not. There have been several engine changes, so only the factory can tell them apart by the number on the mounting lugs.
On the quickie, which has the same cylinder, I used header pipes up to 14cm long for a 9x5 prop. Header length and prop size are inversely related, so you can either use a smaller prop or a longer header if the engine will not get in tune with the pipe.
BTW, use 20 to 25% oil if the engine has to scream!
Old 07-23-2007, 08:41 AM
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Default RE: mvvs 40 old pylon engine

I will post some pics when i can get the camera from the wife (and delete some of her photo's) the overall length from rear of crank bolts to end of prop thread is appox 110mm thats why i thought it might be a 3070 but the thread is m6 with a dia7 plain shank indicating a 3066 so i'm not sure what engine this is

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