55chevygasser wrote:Hi, this is my first post so I hope I do it right. I am building a 572 BBC. New Dart block, Wiseco pistons, Eagle rods and Eagle crank. Everything is new except the crank, I ran the crank in a 511 combo that was a balanced kit from Eagle. My question is do I need to rebalance the crank? I compared the weights of the piston,pin,locks,rings and rods from the 511 and the new stuff and the are exactly the same 1623.0, I did not weigh the big and small ends separately. The new rods are 6.535 and the old ones are 6.385. The new pistons are Wiesco vs The old Mahle which were heavier and the new rings are lighter .043 vs 1/16. So the total weight worked out the same but I don't know if the big end small end is a big deal or not and if Eagle does a good job on their balance kits. This is a race motor and I was turning the 511 to 7200. Thanks for any advise..
robert1 wrote:If you correctly calculated the bob weight it doesn't matter what component weighed what. The bob weight is the bob weight. If it was 1623 and your new weight is 1623 nothing would change.
55chevygasser wrote:Thanks for the replies. I got to thinking about it, since both set ups are using the same rods( except for length ) is there really any difference in end to end? The big ends are the same, I realize that as you suspend the rod further away from the end the weight will change somewhat but at only .150 extra length will it be enough to matter? With the rods being the same (except length) it makes sense that the small end with all it's components weigh the same as the old set up. When I ordered the new pistons and rods the weights they gave me added up the same as the old set up, but when I got the pistons they weighed several grams more than what they said. But I guess with the pins and thinner rings it all averaged out. I have an appointment to have it balanced in the morning but 200 dollars is 200 dollars. I don't know if my machine shop is going to be any better than Eagle. I live in an area that is somewhat performance challenged LOL. I had Dart do all the block work.
rustbucket79 wrote:Trust me, the "balanced" kits from the manufacturers are a very rough balance. Unless it isn't practical, you should have it balanced. I've rebalanced those balanced kits before, and found the difference at 20 grams or more out.
justahoby wrote:not to hijack the thread, but i have a related question. Over a year ago was trying to weigh a big and small end of a rod without a jig. Now I would get totally different readings even at the slightest different angle of what appeared to be even. Now was just curious if there was a trick to checking rod end to pin end without one, on just a scale? BTW i took it in anyway to be balanced as was only $180
Nobody balances these motors so I just went together with it. I called several of the guys doing JR dragster motors and they all said you are wasting your time they don't need it.