Originally Posted by 69chevyLWB
Thanks for your help but i know that the crank is for 6.0 rods now. im just saying that summit said northing at all about needing 6.0 rods. just bought another stroker crank. this one is from eagle because scat doesnt make a 3.75 stroker thats internally balanced that will take 5.7 rods. problem solved. just have to send the crank back to summit.
Actually whether or not you can get to internal balance with either the SCAT or Eagle crank has everything to do with the weights of the pistons and rods selected and whether or not you're willing to step up to the cost of Mallory metal slugs in the counterweights if the pistons and rods prove too heavy for the counter weight masses. This appies as much to what is advertized as internally balanced or externally. If I were you I wouldn't breath a sigh of relief untill this thing shows up at the balancing shop and they mock it up to see whether it'll balance inside or not.
Frankly for a street engine where the RPMs will seldom if ever hit in the upper 5000's or higher the difference between internal external balance is almost a moot point as on a crank pin to crank pin basis even internally balanced engines are not in balance from pin to pin they mightily depend upon the counterweights at the extreme ends of the shaft to put the assembly into balance as a whole. Therefore, there are substantial out of balance forces working on the inboard mains of 2, 3 and 4. This is why 4 bolt blocks are on the 2,3 and 4 main unless you're looking at a real race block that does 4 bolts on all the mains. So the externally balanced engine only moves some counter weight a little further toward the crank ends by placing the final balance up on the flywheel/flexplate and front damper. This puts a little more load on the number 1 and 5 journal while it creates little or no change to 2,3 or 4.
This is not as simple as the advertisers would suggest by data ommision or inclusion. You're not home free till the balance shop speaks.