Factory 71 Chevelle SS, 454, 4 speed, cowl induction hood.

All,

Does everybody else's flapper door suck down (concave) below there hood in the "center"?

I have a 100% complete and working Cowl Induction flapper door set up (internal and external) with all the correct parts. Everything works great, but the external flapper door is sucked down in the center so much, that it actually concaves 1/8 inch below the hood in the center. (The sides of the door are aligned properly with the hood) I purchased a second diaghram thinking the first one was sucking too much, the new diaghram reacted the same way.

Does everybody else's flapper door suck down (concave) 1/8 inch below there hood in the "center"?

Mine looks like it is a little low in the center too but I think it is because the door part is perfectly flat while the hood is slightly domed / curved making it look like the cowl door is concave.

Too much vaccum pulling down the the cowl induction flapper door seems like a common problem. My cars flapper door is also bent inwards in the center. I have a new GM door which I am planning on painting and installing. My flapper door looks like an original and hs had vaccuum pressure applied to it for over 30 years -its going to bend (its pot metal).

My cowl induction flapper also has the valve in there too so I dont know why there would be too much vacuum pulling down on the door. Again, were the original cowl doors perfectly flat or were they slightly domed like the hood?

Resq302,

My old flapper door and new (both GM) do have a slight curve that follows the hood....but the darn thing concaves when the engine is started. I don't want to sound anal, but do you think the GM quality department would have accepted this concave in 1971?

Does anybody have a flapper door that "doesn't" concave?

Resq302,

My old flapper door and new (both GM) do have a slight curve that follows the hood....but the darn thing concaves when the engine is started. I don't want to sound anal, but do you think the GM quality department would have accepted this concave in 1971?

Does anybody have a flapper door that "doesn't" concave?
I here it was acceptable in 71-72 but would never be allowed on a 70. J/K Mine is a little flatter than the hood when closed.

Actually, thinking about it.... I think you are right that it only does it when the vacuum is applied. I remember from when I was cleaning my elky that has the cowl induction hood flapper that when I push it closed (flat) when I am waxing the hood, it is perfectly alligned. I guess it has to do with the amount of vacuum pulling it down.

I put a spacer in there to limit how far the door can be pulled down.