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2015+ S550 Mustang Talk
The 5.8 Trinity Fits!!!
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<blockquote data-quote="Jroc" data-source="post: 13764804" data-attributes="member: 51847"><p>You are confusing what we are getting at. No one is knock ci's. More ci's are great IMO. It's where Ford made the extra ci's with a 5.4 based motor where the problem is. Just like the older SBF's the extra displacement is gain in the stroke of the crank as opposed to an increase in the size of the bore. That's great on a old SBF that came factory with a 4" bore, but a Modular has a 3.552" bore which is extremely small for a larger America v8. I believe a new 5.8 uses a 3.68" bore to make it's extra displacement over a 5.4, but even still a 4.165" stroke is huge for a motor with such a small bore size. </p><p></p><p>There are several negative to this in a performance motor: </p><p>-First it mean you need a tall block to run this stroke. That adds noticeable weight that is carried noticeably higher up in the chassis. That is not desirable in a car that you want to make handle well. It also means on a V type motor that it's going to be wider.</p><p>-Second it greatly limits the amount of RPM's that it can safely spin as a engine with a 5/8 longer stroke(pretty much the increase in stroke between 4.6, and 5.4 based motors) will be turning much high piston speeds at and given RPM than a motor with a shorter stroke. This obviously will create more heat at any give RPM. I've noticed that 5.4's like to come up to operating temperatures much quicker than 4.6's, and the only reason I can figure is the pistons are traveling faster at any RPM.</p><p>-Third you have got to give the rods some room to move side to side, and long stroke/small bore motor like a 5.4 is starting to push those limits. I believe that the the piston slap issue that is common with 5.4's when they're cold is because the stroke is so long and the bore so small that to clear the bottom of the cylinder that the length of the cylinder is less than idea in a 5.4 and it can be noisy when the motor is cold.</p><p>-Fourth why do you think one of the main reasons a 2v 6.2's topend is so much more efficient than a 2v Modulars? Because on a small bore motor like a Modular you have to run much smaller valves. On a larger bore motor you don't need 4v a cylinder to be efficient as 2 large valve will flow air/fuel/exhaust in and out of the cylinder much more efficiently than 2 small valves.</p><p></p><p>I can likely come up with more reason as to why a long stroke motor like a 5.4 is less than idea for a performance application than say a new Coyote, but you get what I'm saying. If Ford build a all aluminum 6.2 Boss based performance motor and got it to fit in the new Mustang that would make me happy as hell. Hell with the displacement capability's the new Boss motors have then give it 429ci's and build a badass N/A high revving Mustang Boss 429. With that said the 5.4 was designed to be a truck motor that made good lowend torque over a broad range. It's originals never meant it to be some high revving topend powerhouse. I'm not trying to take away the potential that the 5.4/5.8 Tritons have, I'm simply saying that Ford has better options for high HP Mustangs with some of their new v8's and the smaller new 5.0 motors are one of them. </p><p></p><p>A old SBF uses a 4" bore with a 2.87" stroke,(289) a 3" stroke,(302) and a 3.5" stroke.(351) Many believe that the smaller stroke/displacement SBF stroke kits are better than the larger ones from a reliability stand point. A 331 stroke crank uses a 3.25" stroke where a 347 uses a 3.4" stroke. When talking 351 based motors a 393 uses a 3.85" stroke, and 408 uses a 4" stroke, and a 427 uses a 4.170" stroke.(pretty much the same as a 5.4/5.8 Modular but with a much larger bore) I've been told that getting over 4" with the stroke is not idea on a performance motor. I'm no expert, or engine builder and obviously you take deck heights, rod lengths, and all that into consideration when determining a good reliable stroke to use, but from what I've been taught is 4" is a good stopping point for most SB's.</p></blockquote><p></p>
[QUOTE="Jroc, post: 13764804, member: 51847"] You are confusing what we are getting at. No one is knock ci's. More ci's are great IMO. It's where Ford made the extra ci's with a 5.4 based motor where the problem is. Just like the older SBF's the extra displacement is gain in the stroke of the crank as opposed to an increase in the size of the bore. That's great on a old SBF that came factory with a 4" bore, but a Modular has a 3.552" bore which is extremely small for a larger America v8. I believe a new 5.8 uses a 3.68" bore to make it's extra displacement over a 5.4, but even still a 4.165" stroke is huge for a motor with such a small bore size. There are several negative to this in a performance motor: -First it mean you need a tall block to run this stroke. That adds noticeable weight that is carried noticeably higher up in the chassis. That is not desirable in a car that you want to make handle well. It also means on a V type motor that it's going to be wider. -Second it greatly limits the amount of RPM's that it can safely spin as a engine with a 5/8 longer stroke(pretty much the increase in stroke between 4.6, and 5.4 based motors) will be turning much high piston speeds at and given RPM than a motor with a shorter stroke. This obviously will create more heat at any give RPM. I've noticed that 5.4's like to come up to operating temperatures much quicker than 4.6's, and the only reason I can figure is the pistons are traveling faster at any RPM. -Third you have got to give the rods some room to move side to side, and long stroke/small bore motor like a 5.4 is starting to push those limits. I believe that the the piston slap issue that is common with 5.4's when they're cold is because the stroke is so long and the bore so small that to clear the bottom of the cylinder that the length of the cylinder is less than idea in a 5.4 and it can be noisy when the motor is cold. -Fourth why do you think one of the main reasons a 2v 6.2's topend is so much more efficient than a 2v Modulars? Because on a small bore motor like a Modular you have to run much smaller valves. On a larger bore motor you don't need 4v a cylinder to be efficient as 2 large valve will flow air/fuel/exhaust in and out of the cylinder much more efficiently than 2 small valves. I can likely come up with more reason as to why a long stroke motor like a 5.4 is less than idea for a performance application than say a new Coyote, but you get what I'm saying. If Ford build a all aluminum 6.2 Boss based performance motor and got it to fit in the new Mustang that would make me happy as hell. Hell with the displacement capability's the new Boss motors have then give it 429ci's and build a badass N/A high revving Mustang Boss 429. With that said the 5.4 was designed to be a truck motor that made good lowend torque over a broad range. It's originals never meant it to be some high revving topend powerhouse. I'm not trying to take away the potential that the 5.4/5.8 Tritons have, I'm simply saying that Ford has better options for high HP Mustangs with some of their new v8's and the smaller new 5.0 motors are one of them. A old SBF uses a 4" bore with a 2.87" stroke,(289) a 3" stroke,(302) and a 3.5" stroke.(351) Many believe that the smaller stroke/displacement SBF stroke kits are better than the larger ones from a reliability stand point. A 331 stroke crank uses a 3.25" stroke where a 347 uses a 3.4" stroke. When talking 351 based motors a 393 uses a 3.85" stroke, and 408 uses a 4" stroke, and a 427 uses a 4.170" stroke.(pretty much the same as a 5.4/5.8 Modular but with a much larger bore) I've been told that getting over 4" with the stroke is not idea on a performance motor. I'm no expert, or engine builder and obviously you take deck heights, rod lengths, and all that into consideration when determining a good reliable stroke to use, but from what I've been taught is 4" is a good stopping point for most SB's. [/QUOTE]
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