Spring for cowl vent damper?
 

http://67-72chevytrucks.com/vboard/a...1&d=1501189078

Curious about the small spring shown in this pic by CUSTOM/10. It appears to aid in opening the damper, but the vacuum servo does that without any help from the spring. When the servo closes the damper, the spring actually works against it just a little. Could it be a backup (failsafe) in case the servo didn't work at all, to open the vent allowing fresh air into the cab? Or does it have some other purpose?

I borrowed a spring from one of my gate latches to see how it worked. If that spring needs to be there, the hardware store probably has one. If it's not really needed, I can put the cowl back on and call it a day.

Re: Spring for cowl vent damper?
 

The general wasn't trying to waste money buying millions of those springs....

Re: Spring for cowl vent damper?
 

This is an original spring. It is really quite "stout".

Re: Spring for cowl vent damper?
 

Thanks for the pic, now I know what to look for.

Re: Spring for cowl vent damper?
 

The spring holds that door open. When vacuum is applied the servo shuts the door. It's the opposite for the passenger kick panel door; with vacuum applied that door opens and the spring keeps it closed when no vacuum is applied.

Re: Spring for cowl vent damper?
 

Yes, I recently learned they work opposite each other.... in fact, I only recently learned there is a cowl vent! :) Mine was missing....

My servo holds the door firmly open with no vacuum, which I why I wondered what the spring actually did. Easy enough to add the spring though, just to make it right.

Re: Spring for cowl vent damper?
 

I lost mine, or it was missing, so I just grabbed a random spring from an assortment, drilled an anchor hole, and used that. It's worked great ever since, so I don't think it's that picky about spring strength (or I just got lucky).

The vacuum servo is MUCH stronger than the spring. Figure 10lbs psi times about 10 square inches of surface area, it could have up to 100lbs of pull force.

Re: Spring for cowl vent damper?
 

There are channels at the ends of the cowl that drain just in front of the doors, whether the truck has air or not.