I just picked up a near complete HP40 and one in need of some internal parts. They're both Austrian made and have bare aluminium cases, so presumably the Silver Star variant as opposed to the Black/Gold Gold Cup version.

Questions:

1. What's the difference between the Silver and Gold versions othr than the colour? I understand later GCs had a ringed ABC setup, whilst the SS were always steel/iron.

2. What can they be used for competitively? One is destined for a carrier model, what else can they do? Speed? Stunt?

3. Are the new Mecoa parts compatible with the old Austrian made engines?

HP-40's make a great stunt engine. I have several in stunt planes now. Have one in my SCIMATAR. Bob Hunt used HP-40's in some his stunt planes.
Most of the ones I have are with the steel liner's. The Silver and black & gold seem to be the same. I have one new Black & Gold that is ABC.
Tom Hampshire of the Circle Burners Club does reworks on the HP-40. He did several for me. Randy Smith has a Tongue Muffler for the HP-40.
You won't be disappointed !!!!
Bill Mazzoni

Bill Wewage run one in a Piroque at the world champs. If thats how you pronounce it .
Use something more common for crasshing into carrier decks .

Thanks for the comments, guys.

These ones definitely have a front bearing. And the removable front shaft housing.
The throttle has an OS needle on the HP NVA and a couple of different HP NVAs in a bag.
Both have cracks in the venturi/throttle stub from overtightening of the mounting screws. I think I might have to drill the holes out and do that the OS way to prevent further damage.

Unfortunately .40 is not a size I am inclined to use for stunt, although I must confess a Novi III with one of these would fit nicely in the long-term wish list.

Yep, both front housings have cracks in the same place, one of them on both sides. The casting is very thin there when it should be quite thick.

Based on my 7-8 years of working in Randy's shop I can say the these are (can be) excellent stunt engines. Extremely light weight, and when properly tuned, very strong. If you want one set up for you, I'd talk to Randy. The general problem with all of these is that they came in many varients, each requiring different "fixes". They kind of faded away because of parts issues and the appearance of the Magnum/Thunder Tiger .36 later converted into the Aero Tiger.

W.