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RJ Sledge · 11-19-2012, 07:54 PM

JimR

The Wizard was trying to tell you in his post, if you go back and re-read it he makes a comment about the difference in C/H of the piston. This is how its done and he also states that the only way to check C/H is with a piston and rod removal request (sic). Don't feel bad about being honest you are in the majority.

Larry

FYI 390/427 are not 3.980, they are 3.780 so the weight loss is only very slight and I don't have a clue about "change in polar moment of inertia" maybe polar movement of inertia is what you meant, anyway its way over my head. But from my 12th grade basic math class that I took for the 3d time I would guess that the weight difference would be about the same as a "popcorn fart" or maybe the same weight as a "gnats ***".

I believe that you are confused about the stroke of these motors and the rod pin size. Yes there would be a difference, but I doubt it could be measured. I may be wrong, and it wouldn't be the first time.

And to answer your question of "why is the 390/427 allowed these rods", is because NHRA approved them 9 years ago and its a little late to be closing the barn door after the cows are already out.

Luv ya Bro!!

RJ

11-19-2012, 07:54 PM	#10
RJ Sledge Senior Member Join Date: Jun 2007 Posts: 783 Likes: 503 Liked 288 Times in 90 Posts	Re: Aftermarket Cranks JimR The Wizard was trying to tell you in his post, if you go back and re-read it he makes a comment about the difference in C/H of the piston. This is how its done and he also states that the only way to check C/H is with a piston and rod removal request (sic). Don't feel bad about being honest you are in the majority. Larry FYI 390/427 are not 3.980, they are 3.780 so the weight loss is only very slight and I don't have a clue about "change in polar moment of inertia" maybe polar movement of inertia is what you meant, anyway its way over my head. But from my 12th grade basic math class that I took for the 3d time I would guess that the weight difference would be about the same as a "popcorn fart" or maybe the same weight as a "gnats ***". I believe that you are confused about the stroke of these motors and the rod pin size. Yes there would be a difference, but I doubt it could be measured. I may be wrong, and it wouldn't be the first time. And to answer your question of "why is the 390/427 allowed these rods", is because NHRA approved them 9 years ago and its a little late to be closing the barn door after the cows are already out. Luv ya Bro!! RJ