[02ztsian]

By undersized what do you mean? Undersize crank journals, lightened crank or offset-ground crank? Undersize journals free up HP due to reduced friction (less total bearing surface) and less distance for the crank surface to travel; lightened crank will spin quicker (rev faster) but can nose over in top gear due to lost inertia; offset ground will increase displacement and increase compression (if the crank throw is increased). These are all old hot rodding tricks and apply to 4's as well as V-8's. Hope this helps.