Join Date: Jan 2001
Location: Lubbock, TX USA
Re: Overbore overheat myth
DjD, how does heat come into the outer part of the cylinder wall from the coolant??? It's dissipated by the coolant, not the other way around - the outer surface of the cylinder is a good bit hotter than the coolant so heat travels away from the cylinder, not into it.
How does having a thicker cylinder wall help dissipate heat? I think it would retain it since it's denser than the surrounding water. Heat travels through the cylinder walls from the cylinder, it should cool faster if it has less distance to travel. The only area of a cylinder that can actually dissipate heat is the very outer surface of the cylinder barrel where it's in contact with coolant, the rest of it either retains it or transfers it.
Big blocks RARELY overheat with a decent cooling system, even if they're punched .100 over or more. That's because folks that build big blocks generally pay closer attention to cooling needs than folks that build small blocks, IMHO.
If there was anything to this myth, aftermarket block manufacturers would include something about it in their machining instructions, but they don't. Cylinder wall thickness for rigidity/ring seal is the only thing they're concerned about.
I think the whole wive's tale got started by folks removing smogger 305's and 307's and replacing them with much more powerful engines including the engine that got this whole myth started, the lowly 400.
The internal combustion engine generates heat. The more power it makes, the more heat is generated and the better the cooling system needs to be.
FCS Harmony Racing
Momma always told me not to look into the eyes of the sun.
"But momma, that's where the fun is!"