[willtwallace]

Originally Posted by blykins

A lot more prep, more chance of a customer doing damage by getting on it when it's not fully up to temp (main bearing clearances change with heat), more chances of leaks, both internal and external. Things like lifter bore bushings require more press fit and even cam bearings have to be Loctited or pinned to keep them from moving when the block gets hot.

Even lash/lifter preload changes at a higher rate. On an iron block with aluminum heads, we see lash increase by about .006" when up to temp....hydraulic lifter preload would decrease by .006". On an all-aluminum block, lash grows by a whopping .015"....which means you lose about .015" of lifter preload on a hydraulic lifter. There are some street solid roller camshafts that I use that have .016"/.018" hot lash spec. That means that cold lash needs to be set at .001-.002".

To add to that, a high performance aluminum block engine will make less horsepower than an equivalent iron block engine, due to the block being less rigid/stable, thus contributing to a lack of ring seal.

There are more areas for liability for the engine builder, just so the customer can say, "Yeah, that block only weighs 125 lbs" or "Yep, it's an all-aluminum engine."

I'm really not a fan.

ummm, well, okay. Hmmm, thanks.