+.060 means very little in terms of overheating. Horsepower = heat. Adding .060 to the bore typically adds < 10 hp, and only then at WFO. You need to look at all the usual suspects: Radiator, fan clutch, fan shroud, coolant level, water pump, thermostat, gauge accuracy, airflow in the engine compartment, ignition timing, fuel curve, brakes dragging, etc.
i think some more info on what vehicle is equiped with, when does it overheat. ie idle, cruising down the road, in traffic
On a 455 .060 overbore definitely adds heat to coolant. Not much left in terms of bore. Years ago I noticed hotter running with even .030. I find the 400 and 430s run coolest.......
Running hot at idle is all a factor of coolant flow and the fan drawing air in well. Charging down the road you need coolant flow also and a fan clutch that disengages so the fan blades do not block the air thru the rad. Other things can be related to timing , cylinder pressure and Carb jetting. What is your timing set at ? Your feeding some 12 more cid now running down the road so your Carb may be lean in its curse and power circuit a tad now and if you have no vacuum advance at part throttle you would be amazed how much heat that will add into the cooling system especially if your Cam is mistakenly installed restarted!
Carolina Drifter, we could use a little feed back here, you already started a previous thread on this issue, http://www.v8buick.com/index.php?threads/60-455-overheating-problems.338022/ We can’t help without you participating.
...at idle or cruise. Heavy throttle will raise the temperature, but when the vehicle goes back to idle or cruise, the temp should come right back down. Of course, electric fans that aren't set to turn on until 220 will affect the temperatures as well.
Was the block honed with torque plate(s)? I see Buick blocks move .004”+ when bolting plates on after boring. I leave .006” to hone, I’ve seen where the bores will have tight spots that have .0095” to hone after the plates are installed. It’s not a problem and they hone fine with plates, but of a block were honed without them, that would be an issue. If you only had .002”-.003” piston to wall clearance, you may now have spots that are .001” tight as-assembled. Between the friction caused by that and the lost ring seal, along with the now thinner cylinder wall, it’s a compounding issue. It's just something to think about. Another thing is plain old tune up. Retarded timing or lack of vacuum advance for low load cruise speeds could be cause for overheat as well. I’ve always been a believer in minimum anti freeze and two jugs of water wetter. Works on my hauler and a couple street cars I have.
Local hot spots in the heads and blocks of any motor ( and they all have them !) will boil water . Steam will not and can not draw off heat from these internal areas then so they get even hotter. This then kicks off a bad revolving cycle of events which at some point due to high steam pressure peaks with the rating of your radiator cap getting exceeded and your overflow tank filling up! Water pumps can not pump steam!
