I've heard people refer to the 6.7 having Siamese piston configuration, I'm assuming this means that (on a 6 cylinder) pistons #1 and #4 are in the same position. How far off am I on this?

 

From what I have read on here the new 6.7 has a simease block not pistons. They do not have water jackets between the cylinders in the block. Hope this helps.

 

OK, I couldn't remember exactly what it was. So with no water jackets in between that means less used space?

 

It means the 6.7 is joined together between the bores of the block , no coolants flows between the piston bores , except in between 1 and 2, it is fluted there for the oil cooler and flows between those two cylinder bore.

 

So how is it to remain cool?

 

ya im kinda scratchin my head here too
would it not make sense the way your saying that there would only be coolant flowing between 2 and 3 and 4 and 5 and then behind 6 ?

i know the 5.9 runs edited by admin cool and keeping temperature is tough to do at idle
but there has to be some kind of cooling goin on

 

Could it be a piston cooling nozzle?

 

Actually there is no passage between 1 and 2 cylinders (or any of the others).

If everyone here can image lining up 6 coke cans in a row. The siamese cylinders are joined like that. There are provisions for improved flow as close as they can get so that there are no cooling issues between the cylinders.
The rest is basically the same as previous years with coolant flowing around the cylinders on each side. Coolant can also flow from side to side at the front and rear of the block.
Siamese cylinders actually add a great deal of integrity and rigidity to the engine block.

 

In that respect, they do allow for a different design of the block and make it stronger in the process. However, the siamesed cylinders introdice some other issues that could be signicficant.

Without the coolant flow between the cylinders heat is not taken away from the cylinders evenly. This causes different expansion rates in the cylinders as they heat up. The rings will take up a lot of this, but, when you start pushing the fuel and the heat the piston is going to expand evenly and faster than the cylinders which can lead more chance of scuffing the cylinders under high stess high fueling conditions.

The solid block also has a tendency toward more issues with cavitation than a standard block. A lot more of the harmonics are translated into pressure waves and the block reacts differently than a cylinder most buffered by water. The block will also tend to tramsmit torsional harmonics a bit more harshly to the drive train.

The DMF is goign to be even more integral in the drive train with this setup and power mods possibly more critical to control.

 

I would say that a fluiddampner would allmost be a necesity by the sounds of it

Kevin

 

The 6.7 has a fluidampnr of sorts, it's a lot different than the older 5.9 dampner. Plus my 6.7 runs alot smoother and more quiet than the 5.9 - could be less harmonics, stiffer block, could be?! Also the 6.7 has a lot more fuel pressure than the 5.9 and I think that quiets them down to.

 

This is what I heard about the siamese cylinders, cylinders 1and2, 3and4, and 5and6 are joined, so there is cooling jackets at each end outside 1 and 6 and between 2and3 and 4and5, so each cylinder has cooling on three sides, just not on the side were it's "joined" with it's "siamese" twin. could be wrong, everyone has a different take on it.
One reason I heard of for going that route was to keep the engine from getting any longer with the larger bores.
I know it doesnt sound good at first but race engines are built that way and it's supposed to help with the cavitation issues, which I really don't understand just repeating what I've learned over the past several months studying this engine since I've invested in one and wanted to know all I could about it.

 

I'm going to tear my 6.7 out of my truck and check it out - maybe all the guessing will stop - or maybe not! Just kidding guys!

DH

 

finally got a 6.7 apart , the cylinders are siamese but they are water jacketed between cylinders also , so coolant does flow between cylinders thru water jackets, all this adds rigidity and strength like Pourin says.

 

You beat me to it BaldHog! Thats good to here - maybe some of these rumors will go away about the 6.7 now, or maybe not!