General Engine Theory, rod length.

[militant_x]

Ive been posting so often now, so many things you guys know that I dont. Anyway, ive been thinking for sometime of building up a 383 400 or 406 based off what I can find.

Looking at the general connecting rod options that are around, everything points to lightweight h-beam type rods. However I dont know why one would pick 6 inch rods over the 5.7 inch rods.

This is what I understand, a longer rod has to put up with more stress and weights more than a smaller rod. Its (only?) advantage is that it mates to a piston closer to the top of the piston, which in turn prevents the piston from rocking in the bore.

So how bad is this "rocking" of the piston. You figure that the pistons for the 5.7s and 6.s should weight almost exactly the same. Yet the rods dont.

Is this rocking effect worth the extra stress on the rod and the associated weight? The weight isnt that much, on the ebay eagle rods its the 6s have about 30 grams on the 5.7s (650 vs 620 i think, dont remember exactly).

Anyway, gotta love random engine theory. So many people have gotten great results with so many different methods... there isnt one right answer, just alot of variables here and there. So what do you guys think?

-chris

 

[Eagle85C4]

You need to speak with Grumpyvette....

 

[vader86]

what you want is an optimum Rod length/stroke ratio, but the difference between these two is still small enough that power differences are not major until a supremely radical combination is in there

I would, and am planning on, running a 5.7" rod for my 383. If I was going bigger and/or wanted a higher revving engine, I would likely go 6".

 

[tntcorvette]

Go with the 6" rod in a 383 stroker and get the better rod/stroke ratio.