Bought a 67 Chevelle HT a couple months ago and have been taking it apart for rebuild. I finally got the AC/heater box, evaporator, blower, blah, blah, blah removed (amidst pounds of sealer, glue, silicon, etc) and found a LOT of rust. It appears water (from rain I suppose) was running into the cowl vent and into the evaporator box where it was probably pooling and dripping into the passenger interior and down between the chassis and fender. Now that everything is out, I would like to know how to prevent this from happening again. Is there some sort of diversion plate in the cowl vent that is missing on my car or is water just supposed to run down between the chassis and fender and find its way out? The water path has completely rusted out the lower fender attachment bolt and hole, as well as the bottom edge of the hole in the firewall where the evaporator was. I don't have a clue how to weld so I probably try to find someone with a portable rig to come out and weld a few plates over the existing firewall holes. Afterwards, I will be installing a new Vintage Air unit. But.....I don't want to close up anything until I have the water travel issue under control. Apologies for the long post. This is my first project in 25 years and I got taken for a ride - the "high dollar restoration" I supposedly bought turned out to be nothing more than new paint and undercoat over the top of years of abuse. Expensive lesson, but I'm learning absolutely everything as I go and will know better next time.

The reason that area rusts out there is because of leaves and tigs getting that cowl vent and falling down into the kick panel area. The way it is suppossed to work is rain enters that cowl then drains out at the rocker panels. But since leaves are now in there they hold mositure and dont allow all the rain to drain out so now you got rust forming.

The only way of stopping this is cutting out the rusted metal and welding in a new piece from a donor car. Welding plates wont stop anything just promote more rust. You need to get in there and remove the rust its the only way to stop rust.

As for stopping future leaving from entering you could install a cowl vent screen which is a small wire mesh screen that goes over the cowl. I know that those screens came on buicks from like 70 and on, and you can buy repo screens for chevelles but I think that they fit 68-72...Eric