Sorry you are having so much trouble with headgaskets. I guess I am lucky. I have 4 mowers now with over 2,500 hours on them collectively, B&C and Kohlar. And I have put at least 2,500 hours on others in the past (know on wood). I do not recall even replacing one headgasket. There could have been a casting problem. Either the head or block is untrue. I remember a race car machinist telling me once, that he had seen a crankshaft linebore 1/4" out of line with the cylinders. He said a motor with a block like that will not last long. I am 88, and have had extremely good luck B&S & Kohlar. Best of luck finding out what is wrong.I have a Husquvarna tractor. 18.5hp. Can anyone tell me why I have gone thru 4 head gaskets? This one being the 4th. Blows out right across from the plug. There is no way I screwed up 3 headgaskets. Getting a little tired of this crap. Are these engines junk? I can change a hot cylinder in a 2500hp EMD but can't keep this running. Should sell everything and buy a diesel....