Rinse out the tank with water. I have soldered a hole on the top of a 74 model tank. My first 164 was a 74, the boot floor was bowed downwards towards the top of the tank which formed a pinch point. A large stone got tossed up over the top of the tank, slid over the front/high part of the tank and it got wedged inbetween the lower part of the tank top, and the bottom of the bowed boot floor. I stuck a short cad plated 1/2" bolt in to the hole, 1/2 fill of water after rinsing it out and stuck some MIG gas in. Chuck a bottle of metho in afterwards to rinse out the water.
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