Re: AU bottom end, what's the deal?
According to Jim Mock, the AU is the best bottom end to start with for performance mods (its on his site sumwhere)...the counterbalances mentioned above have something to do with it methinks. I'd imagine that each time the spec of the engine changed, the cranks changed slightly.
Very few cars come out of a factory with a "fully balanced/blueprinted" crank. The E series XR6's are an exception tho....so there is probably somethign to be gained by blueprinting/balancing the crank...but probably not as much as u'd get from spending the same amount of money elsewhere.
NOTE: Blueprinting is where they grind off all the casting bits (seams?) and make it all nice n smooth.
1987 Jaguar Sovereign - Metallic Green
3.6L DOHC 24 Valve