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Originally Posted by Commander
...everyone is implying that siamesed cylinders can be bored to the extreme of a .10 wall shared by two cylinders. Not so.
a siamesed cylinder works better generally because it is thicker overall, stiffer, less prone to distortion.
it IS connected to the next cylinder(s) along a line though. Heat these cylinders up, and constrained as they are by their neighboring cylinders, you'll get out-of-round distortion. bore these connected cylinders and you'll experience MORE of this out-of-round distortion than you would if the cylinders were free 360* around. So siamese cylinders CAN be good, just don't take all that metal as a free pass to bore the daylights out of them or you'll have ring seating (and other) problems like you wouldn't believe.
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This is the point I was trying to make with my earlier statement "Another thought is how much metal must you have minimum around the siamesed bores for the process to work?". Thanks for explaining what I was trying to say.
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Originally Posted by farmallmta
...While various truck and heavy duty engines earlier had used siamesed cylinder design for low RPM applications, the Hudson 308 inline 6cyl developed in the late '40's and first installed in the Hornet line in '51 had siamesed cylinders and was intended to be capable of all-out sustained high RPM racing. This application most closely tracks our interest in this forum and is probably one of the first American applications of cylinder siamesing as we would use it.
The Hudson 308 engine was a bored version of the 262ci engine which required strengthening as the original design limitations were exceeded. The high chromium content of the block alloy minimized cracking of the siamesed cylinders under ordinary use conditions but an overheated block would occasionally crack under severe (race) use. Despite this, the Hornet was THE car to beat in NASCAR (a brutally harsh racing environment in those crude dirt track days) from '51 up into '54. Anyway, the best overhead valve V8-equipped Olds and Mopars found it very difficult to beat the 308ci (FLATHEAD no less) 6 banger in a Hudson Hornet. The other marques (ESPECIALLY Chebby) were completely outclassed and not even close to being serious contenders.
Doc (The Fabulous Hudson Hornet) Hudson sends his kind regards!
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THANKS for the history lesson, Doc. While I've certainly heard of the Hudson Hornets and their domination of NASCAR, I saw my first one just a few weeks ago at a local car show. When I came upon it, I first thought it was a '50 Merc, but the side sculpting wasn't exactly the same. Once I got to the engine compartment and saw the dual carbs on the straight six. I realized what I was looking at. Neat car.
Dan