Ok the is a question about the difference between the 1/2 A engines of yesterday and the ones people are using today ?
 Are the norvell and brodak and ap just larger (.061 /.74) or is there something that makes them comparible and more powerful than the cox engines of yesteryear ?

Ok the is a question about the difference between the 1/2 A engines of yesterday and the ones people are using today ?
 Are the norvell and brodak and ap just larger (.061 /.74) or is there something that makes them comparible and more powerful than the cox engines of yesteryear ?

Sticking with "true" 1/2 a engines, they are just better, but they do some of their power by turning smaller props at very high rpm. So a very good BlackWidow will turn a Cox 6-3 in the 16-18k rpm range, my Norvel Big Mig 049 will turn a cutdown Tornado 5-3 (to 4.75x3) in the 22k range. As I recall, the Norvel is pretty miserable with that same Cox 6-3 prop that the Black Widow loves.

Now the Norvel 061 Big Mig is a lot easier to tune than the 049 version, so yes if you allow more "cubes" then you will be able to make more power at a lower rpm (or a lots more at a higher rpm).

A couple of other advantages that modern engines have are improved fuel economy and the ability to run superbly on low nitro fuel.  I get over 20K with an APC 6x2 prop on 10% nitro fuel and do the pattern on 7/8 ounce of fuel with the AP Wasp .061.  The old Tee Dee would need 1-1/4 ounces of 25%.

Another plus is that the modern engines are happy with a 50-50 mix of synthetic and castor, so they never varnish up.  The pistons have pins, not ball sockets, so they don't fail.  Finally, the AP Wasp has a bronze bushed crankcase that is vastly superior to, at best, anodized Aluminum of other engines.

No, I don't have a "piece of the action" with this engine, I just am passing on my enthusiasm and feeling that I have found the (currently) optimum small engine.  OK, it is an .061, not .049.  If you want a good .049, you need to find a Brodak Mk 1 and add the Nelson head.

Jim G.,

Missile Mist wasn't bad in C*x engines. Duke's was a bit lower in nitro, so the top end was a bit less, too. Francisco used to make some potent brews, tho.

Another difference I've noticed, that Larry didn't mention, is that the newer engines are much smoother running. Relatively hefty crank webs, Aluminum pistons do make a difference. Just make sure the props are nicely balanced...