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Old 04-10-2011, 04:28 AM   #14
thePill
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Drives: '11 Mustang GT Premium
Join Date: Oct 2010
Location: Kaiserslauthern, Germany
Posts: 1,268
It says the LS5.5 is a de-stroked 7.0 engine. If that's the case, based on the 7.0 has a 4.125x4.000 bore/stroke, then the LS5.5 would have to reduce its stroke to 3.14 to reach 5.5 liters (5.501 exactly). Since this 7.0 already has a 7000rpm redline, reducing the stroke to that extreme could increase the revolutions beyond 8000rpm. For an OHV engine, there would have to be extreme head work done to keep the valves from floating and to keep the engine breathing. I had heard that the valves were 2.18i by 1.60e, the LS7's valves are 2.20i by 2.16e. I heard that the valves have a shallow angle and I have no idea if the 70cc chamber is still being used. The production Gen V will use a completely unique block that is suppose to physically raise the cam in the block, increasing the distance between the crankshaft and the cam. This means the Gen V will have "very short" pushrods while retaining a similar connecting rod length of a typical OHC engine (probably a bit longer, but shorter than the standard OHV rod). That means sturdier, smaller and lighter internals while they "should" maintain or exceed current internal strength. This means a faster drivetrain and valvetrain, capable of stability over 8000RPM. The next issue would be breathing, as an OHV engine chokes at higher RPM because of a single intake valve. The valves will have to be large, the lift and duration will have to be similar to the LS7's (.591 lift intake and exhaust and a 230/211 intake/exhaust duration) if not more. The LS7 has very big valves, the cam lift and duration would need to be taken higher on both specs to breath above 7000RPMs. Depending on the angle at which the pushrods enter the head casting, it may no longer be required to offset the intake rocker arm. It is my understanding that the cam is being raised inside the block (not pictured above) to increase the angle of the pushrods greater than 90 degrees in order to clear both the intake port (ie old OHVs such as the LS2) and to clear the head casting where direct injection would go (ie LS3,LS7). It is whispered that the direct injectors enter the head casting below the intake port on the intake side of the head. I am trying to picture this but, the injectors and fuel lines are probably going to be housed inside the intake valley, facing outward toward the piston and spark plug.

Edit: You can bet that the production Gen V engine will not have a 4.125 bore and a 3.14 stroke. The engine will probably be a square bore/stroke, I would guess between a 3.80 and a 3.90 bore. By using a 3.81 bore and a 3.85 stroke, we can get a 5.739 liter (350.17 cubic inch). Or using the LS3's 4.06 bore, we can get a 350.30 cubic inch (5.741 liter) engine using a 3.383 stroke. I know everybody has got pretty use to the 6.2 but what is the sense of producing a more efficient engine if GM continues to use the larger displacement. If GM can make a 5.7 liter that produces 450hp, 7000rpms at 27mpg then I would opt for the 5.7.

Last edited by thePill; 04-10-2011 at 10:24 AM.
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