Are there any diagrams that clearly show where water drain holes should be added and to make sure factory holes are there? I looked around and read reference to them but didn't find a diagram. I can't get to the paint shop very easily and want to send the shop clear instructions. The car is finally getting painted. Thanks!
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Placement is not critical. Frame rail drain holes were invented back in the '70s when someone noticed that after driving in the rain, the right side horizontal frame rail was FULL of water that did not drain naturally. And at the time, everyone was terrified of terminal rust in the suspension. If you look closely, there are sheet metal doublers in a few places within the rails, so most try to avoid them 'cause it only makes drilling upside-down harder.
Drilling three 1/2" holes a foot or so apart on each side, starting with the big oval hole on the top right, seems to work. Incidentally, that oval hole is perfectly positioned to catch overflow & drips from a loose rad cap, which also helps fill the rails up. But first, fish around in there with a long piece of stiff wire. I found fair sized rocks, lost bolts and a broken spark plug rattling around inside my rail! Magnets won't catch rocks or sticks.
Adding 3/8" holes at the very bottom of each of the horseshoe-shaped A-arm support legs on the wheel sides of the rails, will usually drain out a half cup of talcum-grade dirt & rust particles. How it got in there, not too sure but if that stuff can get in, so can water to make mud....
Finally, there are factory drains built in the rocker panels that should be cleared. They're odd- a long oval hole with a piece of sheet metal down the center. The rockers are made in a vee with a full length central divider to stiffen the assembly, which is the piece you see in the center of the drain holes. Minor accidents and the uninformed often bend the dividers sideways, pinching off half the space intended to be drained. Multiple paint runs can also close them off. A flat blade screwdriver works well to restore the dual drain function. I think there are door drains usually full of paint, dirt & rust, too.
Thanks Bosswrench and Rocky.
The body is original and rust free. Nevada car. My goal is to keep it rust free. We have cleaned out the rocker panel and door drains.
Boss, Do you mean the frame rails running from the front of the car all the way to the back located at the bottom of the car? "Drilling three 1/2" holes a foot or so apart on each side, starting with the big oval hole on the top right, seems to work. "
Rear lower subframes only. They end just past the rear firewall. The lightly loaded front frames start just at the front firewall and seem to cause no problems. Nor do the upper rails.