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Old 01-23-2011, 07:56 PM   #10
Dare to be Stupid
bgoodsoil's Avatar
Joined: Jul 2008
Location: Washington, DC, USA
Oddometer: 4,645
Man, you guys know your stuff
t seems to me that Siebenrock went to longer rods for the same reasons the Harley guys did: Because they had to for running out of room hogging 'em out! A rare few of the HD guys figured out that they were getting performance gains beyond what the added displacement should have got them and narrowed it down to the longer rod length ratio. It seems that Seibenrock doesn't touch on that aspect of their big bore kits much.
I've heard Harley did an experiment and got incredible gas mileage from a single piston engine by having a very long stroke. I wonder if this is related?

The biggest issue will be pistons though, keeping the same stroke with the same heads and jugs will mean pushing the gudgeon pin further towards the crown which will generally mean moving the ring lands closer to the crown as well. Obviously you can go only so far.

Therefore you increase the rate of failure on the piston as the higher the ring lands the weaker they will be 9they will be made closer together) and the top ring land will be a lot more susceptible to detonation damage.
I think what you're calling a gudgeon pin we call a wrist pin. If so, I get what you're saying there. What do you mean by ring lands? The grooves for the rings? Maybe the stock pistons had acres of useable space so they're not pushing the limit on that? I thought Siebenrock's kit was well-vetted. I wonder who designed that thing?

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bgoodsoil screwed with this post 01-23-2011 at 08:03 PM
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