Perfect crank balance

[dnegative]

On Thursday night I was at a work function at the pub talking shit as you do, topic turned to cars and me and this other bloke were talking about evil nissaids and skylines. Blah blah blah mine has 400hp with some $3000 turbo blah blah blew engine up blah blah. Typical Nissan shit. Anyway, there was this old pommy bloke with us who had just landed from the UK and something about skyline tweaked his memory. He told us that a decade and a bit ago he was working for some outstanding engine building mob that used to build old school race engine (British crap 99% of the time) but one day he was asked to build a RB26 bottom end for some exhibition car.

Anyway, said they shipped him a JUN crank from Japanland along with a heap of other super expensive top notch gear for this build. Before assembly began he tested the crank (now, he told me they had some super super expensive balance machine of which only 3 existed in the UK (McLaren and someone else had the other two that were designed to balance parts for jet engines), he said for a crankshaft it was what you would call spot on but it was still out by a tiny bit. He told the customer who in return asked "how well can you balance it?" Which the answer was "perfect balance if I wanted get it but having a perfectly balanced crank is not idea. You want a very very slight imbalance"

Customer argued the point, lost the argument and the crank was balanced up a bit but not perfectly. Said the bottom end he built held over 1000hp, never had any complaints.


Anyone have any ideas on this?

[Sam_Q]

not ideal to have an perfectly balanced crank? I don't see why

[ballpencil]

the problem is how much is "slight imbalance"? next thing you know, you'll any semi competent, lazy machinist using this as a reason for a crappy work.
i also see there's no reason to have a slight imbalance.

[dnegative]

It was a brand new Jun crank, I'm not sure how well they come from the factory but for $6k (or whatever) you would think it wouldn't need touching.

[jonathan yee]

well anything new is made withing tolerances. any machined parts (rods/pitons) generally will be adv "balanced +/-1g or something. and depending on said machinery you'll be able to measure balance to a finer degree. but i call BS....you were after all at a pub.......and he was from the UK......

[hosking1991]

ive seen many aftermarket v8 chev, ford etc stroker cranks that claim to be "pre-balenced" and the fuckers were so far out they nearly jumped out of the balencer!

the sunnen balencer at my old could work as fine as .001 gm

[fixeruperer]

drunk pom = nuff said.

[oldeskewltoy]

I wonder........... might he have been talking about frequency balancing????