A question about oil burning furnaces

My wife has this in-floor oil furnace in an old house. It was old and had seen better days. When it was replaced, she was sold a new one with lots more BTU capacity than the old one, and told that they didn't make the old one any more. Even though the new one looks identical to the old one in every respect...
I forget the exact specs of either of them.... But anyhow, the new one short- cycles (entirely predictable). Last winter I tweaked the thermostat a bit to increase the dead zone slightly - any more and it would be uncomfortable, but it still short cycles.
My question is how is the BTU output determined? Seems to me that the air intake around the combustion blower has a pretty wide range of adjustment and includes fully closed. Is it possible to just put a nozzle with more restriction in the oil jet, then reset the air mixture? The oil pump has what appears to be a pressure relief that returns XS oil to the inlet of the pump.
I'm not planning on doing it myself, I'd just like to know if that's something that could be incorporated at the beginning of season pre-flight checkup she insists on?
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On Mon, 18 Jul 2011 09:17:10 -0400, default wrote:

    Yes. RTFM.
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<default> wrote in message

your first an biggest problem is

sounds like its is grossly oversized for the house. A smaller nozzle and having the fuel/air mix correctly adjusted isn't much more than temporary solution that will create problems in the long run.
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On Mon, 18 Jul 2011 09:17:10 -0400, default wrote:

Thanks guys. The PDF file was especially helpful. More than I ever wanted to know, but none the less interesting.
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