GM HD News, 6.6L gasser!
35,500# max towing 43,500# max GCWR Duramax is still 445hp/910tq, but has the 10 speed auto New updated frame Same 12" rear diff as the Ram 3500, no word on whether they use a 3.73 or 4.10. No ne...
Forum Discussion
RCMAN46 wrote:73guna wrote:
Siamesed cylinder bores, cooling holes between bores.
Sound like the 400 ci of days gone by.
Is there an issue with the Siamese cylinder bores?
According to a little research I just did Siamese cylinder bores means no coolant holes between adjacent cylinders. However, in the video it is said that these are Siamese with some small coolant holes in between so I am not real sure what to make of that. Also, there are two reasons to make Siamese bore engines. The first is that there simply isn't room, probably due to making 6.6L engine with the same bore spacing as 5.7L engine. The second would be that the spaces were filled in to make the engine sturdier to handle more horsepower, primarily in short lived race engines that also don't have to meet pollution standards.
It sounds to me like in spite of GM saying that this is a "no-compromise" engine the Siamese bore is the result of a compromise. Probably to reduce the investment in new tooling needed to make this engine. I know that a in similar video on the new Ford 7.3L they brag about having the cylinders spaced out enough to put in coolant passages.
I am not ready to discount GM's engine designers but the Siamese design does sound like a potential week point to me. I hope that they have it figured out. It certainly doesn't sound like something to brag about.
