From: [email protected]
Date: 04 Mar 2002
Time: 22:49:43
Remote Name: 195.17.162.2
I think some all important words are missing here, and they are " all other things being equal." There is little doubt that the improved thermal conductivity of an aluminium head would remove some heat which would otherwise been converted to work, however there is more to it than that. The big problem (well one of them) with side valve engines is controlling the heat distribution inside the combustion chamber. Local hot spots cause pre-ignition, and cooling problems, resulting in less than ideal ignition advance and compression ratios just to keep the thing running. An ali head goes some way to curing this, and that is the main reason for using one. One might question however how many engines get this close to the edge and actually NEED an ali head. In these cases, and assuming similar design, I think the statement is probably realistic.
Alan