Why would you use a 6 inch connecting rod v.s. a 5.7" rod? What are the advantages/disadvantages?

 

Rod/strock ratio, its better for high rpm to have a larger number than a lower one. Take for example the SBC 302 which had a 5.7 rod and 3.00" strock, with a ratio of 1.9 and they were known for the high rpm potential. The SBC 400 had a 5.64 rod and a 3.75 strock so the ratio is 1.5. In the same way the SBC 350 is 1.64.
With high ratio the angle of the connecting rod will be lower in relation to the piston at both TDC and BDC and hence less force on the engine block side walls.
At least thats the way I understand it

 

I'm just parroting something I've heard before, but the longer rods give you

"more dwell time at top dead center".

As far as more leverage, I'll be posting at the end of the week if that really is true. So, check back on that one.

As far as the ratio with stroke and rod, don't professional engine builders shoot for a ratio WAY better than the marginal gain of going from a stock rod to a 6" rod?

Ben T.

 

Really all of that other stuff doesn't mean much, It's the lighter weight pistons. That's the biggest advantage of the longer connecting rod.

Bret