Tom_M wrote:
My '87 BMW K75 motorcycle has an all aluminum sleeveless block. As far as I know there have been no issues with it. But then there was the Chevy Vega with a sleeveless aluminum block which had major problems mainly because it had a cast iron head. The different metals did not play well together.
Yep. For years engineers have played with high silicone content aluminum alloys for use as cylinder wall materials. (other materials as well, hard chrome, nikasil (air cooled aircraft engines) boron nitride, teflon, etc. to name a few) As you mentioned, in your BMW, they can work fairly well. Unfortunately in the GM engines (Vega) they didn't work out at all but, IMO, not because of the aluminum cylinder walls. The cylinder blocks were easily damaged by overheating which caused the 2 center cylinders to warp away (inline 4 cylinder) from the head/head gasket causing a MASSIVE coolant leak. Game over. The silly design of the water pump (drive shaft too long) would cause most of them to fail at about 50,000 miles dumping the coolant out the driveshaft seal. One trip above the boiling point was all it took.
I've used ridge reamers in American iron (50's, 60's, 70,s) all the time just to get the pistons out of worn cylinders without breaking the rings/ring lands. I've never seen cylinder ridges lock up an engine. I'm not saying it cant happen. Just that in my limited experience, I've never seen it. IMO, if your engine is locked up, (seized internally) . . . . you probably have much more serious issues.
Chum lee
