I agree with Bob mostly except for one minor thing. It seemed to me that when I went over my engines the aluminum block one had more bolts that would back off just a little. But I would check all the bolts and torque them on both engines any time I ran them hard and if I was just driving them, I really never noticed much difference in the upkeep. I always got under the car and on top of it and checked all bolts and hose clamps and everything after driving anyway, so they never went for any period of time without being checked. I now only have the iron blocks and they are great for what little driving I do.
Ron
