RB crank teck question

[niteshift70]

Just for grins and giggles, couldnt you shave quite a few grams by cutting your 440 steel crank counterweights down to "b" engine size (.360" smaller) and balancing from there to use in a 440 build (or do the same for the stroker cranks)? That would shave roughly 250 grams of the starting weight and reduce windage at the same time. Seems like it would help the engine rev quicker. Any thoughts?

 

[A383Wing]

doubt it...the counter weights are that heavy to compensate for the heavier rods and pistons in the "RB" engine compared to the smaller rods and pistons in the "B" motor

 

[niteshift70]

Going to light weight rods and pistons, which i would think your doing anyway, would make up for that difference as well. I mean the counterweights were originally designed with heavy OEM rods and heavy OEM cast pistons in mind. Just kinda thinking along the lighter weight - less stress - more power line.

 

[62 Dart Convertible]

If you are using lighter than factory rods and pistons, then naturally the crank counterweights would need to be reduced the appropriate amount to achieve a balanced assembly....

and yes, a lighter rotating/reciprocating assembly is better..

 

[niteshift70]

Its been quite a while since I built an engine (28 years and on a chebbie budget at that.) One of the best tricks was going to a longer than stock rod/shorter piston to increase torque (more leverage) and hp (less friction) with the stock stroke (chebbie's 1.5 rod ratio needed all the help it could get in the torque dept). I have been wondering why there were no similar combinations for stock stroke mopars. That being said, i have just read several builder's articles on crank theory stating that any effort to gain mechanical advantage with longer rods produces negligible results once you reach 1.75 to 1.8 to one rod ratio, which makes the "RB" mopar the optimum set up in that dept. "POOF!" That question has been answered (although a shorter lighter piston would be nice.) I guess now the question would be, "Are the modern lightweight H beam rods and forged pistons light enough to be able to lighten the crankshaft that much?"

 

[Meep-Meep]

You are teetering on a multiple page rod to stroke ratio discussion (again), but to answer the counterweight question. Yes, you can remove metal from there IF your rods and pistons are lighter than stock.

 

[Seventy]

I have seen this on race engines, they use light weight rods (and lighten them more), custom pistons, and lightened crank, you can take lbs off the rotating mass of a big block...