Well, the 5.4 cannot legally be used in NASCAR due to it having overhead cams.
Engines must be production units (Ford must have a waiver) be no more than 360ci in displacement, be carbuerated, and be of overhead valve type.
Under those rules the 302 could run in NASCAR, but the 5.4 couldn't. If it did run it'd clean house quite frankly.
Seeing as though the restrictor plates are all the same size, they can only flow so much cfm. The total hp they make with the restrictors is around 600, without, 800 if I'm correct. Now, that is 75% power if 800 is the maximum potential of the motor. The 302 is 87% of the displacement of the 351, so if the 351 can make 800, the 302 would have no problems making 600 and being competitive with the restrictor.
You would have to determine whether or not the 351 could create a significant vacuumm effect and pull more air through the restrictor than what it's technically rated for. That would be kind of a reverse ram air. If it can, which would be more effective, the longer slower pull of a 351's greater stroke, or the shorter faster pull of the 302? In my experiance with fluid suction devices, a long slow pull is more effective. If that is the case with these restrictor plates, then the 302 would be at a disadvantage. That is of course assuming the vaccumm created in the intake can actually pull in enough air reliably so as to not throw itself out of balance with the other components. IE: the heads and cam are built to flow 1000cfm and the restrictor is built to flow 900cfm, the 351's vacuumm effect allows for 1000cfm to flow through reliably. Otherwise, the engine wouldn't be optimally matched, right?
Can somebody help me out with the restrictor plate question? If the restrictor plates are flow tested for a certain cfm, can an engine flow more than the max by creating a negative pressure vacuumm in the intake manifold? Would such a vacuumm be reliable, or would it starve cylinders and become detramental? I would assume its no different than having a small carb on a motor, say 369cfm 2bbl. With that 2bbl and everything else being setup for maximum performance could a 351 pull more cfm through the carb than a 302, reliably?
I guess the questions I have are
[list=1][*]Is the friction of the longer 351's stroke less than the friction of the 16% greater engine speed of the 302?[*]Does the greater weight of the 351's moving parts outperform the additional weight from spinning the 302 16% faster?[*]Can the 351 flow more through a regulated cfm restrictor than a 302, assuming both are tuned to flow the maximum cfm possible through the restrictor?[*]Would a 351 spinning at 7800rpm be more fuel efficient than a 302 spinning at 9000rpm?[*]Would the extra inertia inherent to the 351's greater rotating mass overcome the 302's ability to spin faster allowing for a more stable top speed?[/list=a]
Why hasn't the 302 been run at a NASCAR restrictor event to find out?
My thoughts
[list=1][*]No, the 302 is more efficient.[*]No, the 302 has less rotational mass.[*]No, the vacuumm has to balance allowing maximum flow to be roughly the same, especially considering the closeness of the different motors currently run when the motors have different strokes.[*]No, the 302 is more efficient inherently, therefore even with the additional rpm required, it would still be more fuel efficient.[*]Yes, the 351 with the same amount of hp and torque, at the same rpm levels will outperform the 302 in a flat out top speed run on a banked oval track due to greater inertia associated with it's reciprocating mass.[/list=a]
Perhaps the 302 is not run do to needing an additional waiver for a now non-production engine, or perhaps the old idea of "There's no replacement for displacement" rings true to many of the engine builders in NASCAR, or possibly the engine builders have been studying and designing the 351W for so long, they don't consider viable alternatives do to the research and design costs.
BTW, this is the kind of stuff I think about all day long. Jeez... I need some quality summertime with my car. We're supposed to get up to 12" more of that white **** .
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