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Hmmm ..... Just another of the thousands of things i do not know about .....

I see that on the US820 exhaust ports they are round or close enough to be just round do these engines respond the same way like the Mac's when their tear-dropped or dog-eared out, in the latest owners manual i have on Mac's it kinda says the bigger the better but don't lift the port.

Mc Bob.

I'm almost sure my 820s have "eyebrowed" exhaust ports. Eyebrowed is the term karters use, dogeared is another good one.
I've got an old pair of junked out Big-J 820s and I don't think they have the eyebrows. I just keep them for reference in order to build some more at some point.
The Copperhead 8 ports and piston transfer holes are quite similar to Big-J 820s at a glance.
I don't know what the Copperhead 8 port specs are but on a Big-J 820 the deck is 1.300" above the top of the boost ports, the ports are .300" wide, and .450" apart. The transfer holes in the piston are .550"
Your Copperhead should work good on the root wacker or whatever that thing is.

" Your Copperhead should work good on the root wacker or whatever that thing is. "

Now now Tom, Root Wacker Hmmmmmmmmmm.

I feel the need for speed coming on as i'm not far away from tugging on my what-sa-ma-call-it for the very first time.

It will be interesting to see how it performs against my Mac's but it's only early days yet maybe if i start rubbing a few bits together it will light it's fire.

Mc Bob.

Hey, McBob! I hope you're going to be "tugging on your what-sa-ma-call-it" where nobody can see you! Good luck with the Copperhead! Ted

Bob, about stroking that root wacker 820, I would try and find a shorter stroked crankshaft than the +.200" Horstman crank, say something around +.100" stroke and then punch the bore out about +.120" That way you will keep the bore/stroke ratio about what it is now, won't need to raise the wrist pin location, and the piston will not pop past the deck too much. The standard chamber Horstman head with a thick copper head gasket should be in the ball park also.
I think Dave told me there is a Saab piston blank the correct size for 820s.
The other thing is have the bore done with Nikasil instead of chrome.
I've been thinking about cutting some 820 cranks in half thru the arm in different locations and then welding them back together. The only drawback with that method is it takes 4 cranks to makke a pair of strokers.
Tom