What is ment by siamesed block vs standard for the Hemi?

Discussion of Hemi crate engines.

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What is ment by siamesed block vs standard for the Hemi?

Post by biggymu » Sat Jan 29, 2005 7:45 pm

I had just been reading through some of the forums and had seen different part numbers for the Hemi siamesed bore blocks versus standard bore. For those of us who are unfamiliar with the difference, could someone please explain why two versions exist and what exactly is a siamesed bore? Is one preferred over the other? Why? Any help is appreciated .And thanks up front. Biggymu :)

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Post by cuda70 » Wed Feb 16, 2005 4:00 pm

I see allot of folks have past this question by. After thinking about how to phrase I see why. Siamese bored blocks are not brand new they have been around for awhile. A Siamese bore is where the cylinders are sharing sleeve medal thus the outer cylinder sleeves are touching. The advantage of Siamese bored cylinders is more room is available for larger bore sizes (or thicker cylinder walls for strength) I'm guessing the name Siamese bore comes from Siamese twins (conjoined twins) where body parts are in contact.

Many will argue but the disadvantage of Siamese bored engines is that there is no water passages between the cylinders thus the engine runs warmer. Some Siamese bored engines come with small water jackets drilled between cylinders to help with cooling but is still not as effective as a cylinder that is completely surrounded by water like a standard bore.

Many builders say that Siamese bored are just fine and you will get more cubic inches out of the same block size. Conventional wisdom suggests if you want as much size and power as you can get Siamese bored blocks are the way to go. However it is also believed if a given size can be obtained by a standard bored block choose the standard bore.

Hope this helps!

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