Hello guys, hoping someone here is more familiar with this engine than me. A friend brought over his 455c backhoe that someone had borrowed, because when his friend brought it back, it wasnt running bright. Had tons of blowby coming out breather tube, getting hot, and was not running on all 3. I figured a bad headgasket. I pulled the head and sure enough headgasket was blown between cyls 2 and 3 and had migrated to a push rod passage, hence the blowby. Checked the head and block with a straightedge, block was flat and head was less than .002 variance. Installed new victor headgasket from carquest, torqued bolts to spec( according to dealer) and sequence, i have that chart. I also installed new injectors as per owners request of harder than usual cold starts and one cruddy looking injector. Fired it up and it immediately blew headgasket out side of block. Pulled head back off, called another dealer, not the previous one as their people skills were horrendous, but they were closer. The smaller mom and pop dealer, much more friendly, asked my engine sn and said it should have 9/16 headbolts, which I verified. I gave them the torque spec from other dealer and they said that they gave me 1/2" headbolt specs, not 9/16. Didnt know there was 2 different head bolt diameters, never mentioned. Good deal, 170 ft lbs is much more than 115 (which I thought was kind of light). Ordered new headgasket from New Holland, all new head bolts, cleaned everything properly, tapped bolt holes, lightly oiled, torqued cold as it says, put all together, ran it, got it warmed up, has slight blowby, 5000 hours normal amount, then worked it, it got up to about 210 degrees which seems hot to me, running good, good throttle up. Then blow by starts getting worse and worse until it rolls out from the breather, and still throttles up, seems sluggish now though. Let it set overnight, starts right up, runs good, warm up, work it, then blowby starts increasing again. I dont know how long the other guy ran it with bad headgasket, he isn't mechanical and wouldnt know something was wrong. Engine oil is new and clean, coolant has no oil in it, and no bubbling in radiator. Cylinders and head looked great to the naked eye upon close examination. Im trying to help my buddy out but don't want to have to keep buying $100 headsets, as Ill eat the first one since it was my own fault. Im not real familiar with fords diesel in the tractors and equip though. Im hoping it might be a cracked head or warped head, because I don't have the time to get into the bottom end. Maybe a crazy fuel problem? I know, not likely. Hoping someone out there knows something about this engine. Sorry for the long post, just trying to be thorough, and cover all my bases. Thanks, Ross