Unless you have a forged crank especially machined for external balance all domestic BMS and off-shore cranks are machined for internal use.
Over the years, we have had a few runs of forged cranks built with external balance for owners like you can have a forged crank w/o the additional expense of new flex plate or balancer.
Street engines very seldom see more than 5-6000 RPM even at the occasional track visit, and at this level it will make no difference at all between internal or external balance.
What can make a big difference is using a stock, 30 year-old, hammered stock cast crank with a high fatigue factor over a new forged crank.
Some guys brag about their stock cast crank in the 10's or even 9's, so a external balance forged crank should not be reliable there?
Racers subject their engines to high RPM and boost levels, hard launches and brutal shifts and break a lot of stuff so their upper limit of reliability may be slightly raised and if the trash a crank, flexplate or balancer, it can be easily replaced out-of-the-box and continue on with their fun.
Bottom line in my experience and opinion, unless it is a very high output race engine, external will be fine in most all V-6 turbo builds.
We have an out-dated engine that is over 50 years old when first built, and most all modern engines are now internal balance as that makes production and repair much more simple.
I do stupid stuff when bored like now using a production 4.1 block in my race car to see how long and fast in the 9's it will go without coming apart, so maybe I should next use an external crank to see how that works out?
mines a low ten second build
