So I bought a used b1550hst-d 4wd and got a good deal on it. The only mechanical issue is it has a blown head gasket on #2 cylinder. So while reading through the repair manual it talks about taking a "fuse" and putting it on top the piston with the engine on tdc and setting the head on the block and then looking at the fuse to see how much it crushed. This is all they they talk about with a fuse. So my questions are, they talking about an old style glass fuse like a Buss AGC? And does this play on the piston or? My next question is in the head gasket kit it comes with the gasket a shim. Is this to determine weather or not to use the shim after having the head pressure tested and surfaced? I'm an auto tech for a living but never had to worry much about clearances when doing a head gasket on a vehicle but other than this it is a simple strait forward repair. Thanks any info or input is greatly appreciated on this.