36hp deck height / compression / cam setup..

[Bub]

Ok guys-
hopefully in the next couple days I have all the scraps here to put this back together. I built this engine a couple years ago with 40hp/ 83mm big bore kit and it has run fantastic- almost 8k miles. BUT, it was just an experiment that I knew I didn't intend on leaving as-is forever. So I re-thunk the final build I wanted to have. I'm going down to 80mm p/c's for better cooling and less blow-by.
But give me some opinions on these specs :
64x 80 stock internals.
Original heads just rebuilt w/ 32.5mm intakes
WW Cam
WW 32 PBIC's
*might take 3-4lbs off the flywheel.

So, the 80mm p/c's end up with slightly less deck than the 83's.
I'm getting .025" deck height , ~ 46-47cc volume in the heads.

That deck is pretty tight- but? Can I get away with it on a 36hp @ 7.5:1 with the cam and intake specs ? Compression is fairly conservative, I had it @ 8.4:1 with the 83mm pistons/ stock valves and never had any issues.

And even if I can get away with it- how much is a flycut on the heads going to get me if I shim the deck to .040 and bump the CR up?
With what I have- what would you do?

oh yeah, and I had this wacky idea I may try on a spare exhaust.

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[esde]

I have spoken to many 36hp enthusiasts, and they have all generally said the same thing, which is to not be afraid of raising the compression. On my zwitter engine, the heads are cut a little more than 2mm which gave just over 8:1 (stock stroke and bore). Alstrup understands the cam-compression relationship very well, as he has built so many of these engines. I'd wait for him to comment
Shaving the heads on a stock engine does create a few obstacles: intake and exhaust will need to be narrowed, and pushrods shortened. It's just time if you can do the work yourself.
*edit* I see the dual carbs, so nix the intake narrowing.
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modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[Bub]

I probably wouldn't even be bringing it up- except there isn't a single machine shop within 130 miles that can flycut a head.
So I am kind of screwed.

I do have a place I can get another set of heads already done- to the specs I want, but it's another $700.
As it sits with the .025" deck and 46cc chambers I'll be running 7.5:1. So, ...what am I missing out on with this fairly conservative setup?
3-4hp? maybe FIVE! I"ll admit it's a large difference in this case.

Just had a big huge flood mess in my basement yesterday so doesn't look like the $700 for better heads is in the budget. So Maybe I'll just run it like this for the summer and revisit it next winter if I feel like it's worth it.

Good news is I found a running 36hp locally for $250 and the guy is dropping it off in a few minutes. Why! Yay! Because .
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[Braukuche]

[esde]