rcuser004

My Feedback: (287)

I just bought two .074 and two .061 plugs from MECOA. Thanks for letting us know the .074 plugs were back in stock.

OK all you Norvel veterans, particularly on the Big Mig .074 engine. I currently have three Big Migs; an .049, an .061 and the .074. This afternoon I ran all three and checked rpm on each one running a Tornado 6x3 prop. Readings are as follows:
Big Mig .049...17,500 rpm
Big Mig .061...19200 rpm
Big Mig .074...19150 rpm. I also ran an APC 7 x 3 and got 15600 rpms.

Here is my confusion! How is it the .061 can out turn the .074 on the 6 x 3 prop? Is the .074 a torque engine to run larger props? I would have thought the .074 would be at least 1000 rpm higher than the .061.

Your comments will be appreciated.

Thanks,

aspeed

Nelson plugs are a bigger diameter. Merlin makes them still. Al is getting a bit older now too. They take the regular plug clips which is nice. The Nelson plugs would not fit in the button, a threaded piece would need to be made up. I was just going to make an insert up for a turbo plug and even it is barely going to fit in the clamp ring hole. .315" thread and a .360" hole leaves a very thin wall. I see you snuck in on me while typing. Interesting the .06 being faster.

hllywdb

A couple of reasons Mike. The 061 you have seems strong with the 6X3. Most likely the 074 isn't fully broken in yet. Usually around a 1/2 gallon of fuel you should hit 17k with the 7X3. All three of mine will do that or better with an APC 6.3X4, which is a really nice prop. Speed and thrust.

The 6X3 is, IMHO a bad prop for both motors, so i'm not surprised by the numbers. The 061 is better with something more like a 4X4 or 5X3. I usually start with a 4.2X4 and trim it until I see north of 25k on the ground. You are correct in that the 074 likes to swing bigger lumber. It's not a screamer like the 061's but pulls more like a 10. So it depends on the application. The 074 will pull a bigger plane around with authority, while the 061 shines with something clean and small. That being said the 061 can also be proped with a 5.7X3 and pull most 1/2a planes around like a strong TD, but with the bonus of having a throttle and the reliability of an old straight 6 chevy.

rcuser004

My Feedback: (287)

All three engines are brand new. I ran a few ounces through each one when taking the RPM readings. Thank you for your input.

Andrew

Unlike many small displacement engines that break-in with a few runs (COX is a classic example), I think you'll find that the NORVELs may take considerable running to come in to their full potential. The NORVEL .074 is a great little engine, well behaved and with good pulling power. The APC 7x3 is a good match to its power curve.

If your engines came from NVEngines, there has been some discussion that their offerings have not matched the earlier models that were produced by the original NORVEL company. I expect NV is simply assembling engines from an existing stock of parts without taking care to carefully fit parts.

Mr Cox

For the .049 and the .061 it sounds about right, the .061 sounds even a little above average, but the Tornado props are also lower in load compared to other 6x3 props. The .074 sticks out though, it should do a lot better. I like the APC 6.3x4 and it should do around 17000rpm on that prop, and the APC 7x3 should be a similar load. As other have said it might just need some more running, they keep improving well after one thinks that they are fully run in...

The .074 also comes with 3 head shims I think, so you can try to remove a few after some more running of the engine.

aspeed

Just looking at my notes here, Big Mig .074 18,900 no muffler, 10% fuel on a 6 - 3.5 MA prop. It is fairly new as well.

rcuser004

My Feedback: (287)

Mr Cox:

Thanks for your help. It is appreciated.

Best Regards,