I need to find out how the vacuum part of cowl induction is supposed to work. Is the in-line vacuum valve supposed to be installed with the brass end towards the intake manifold? Also is the vent (on top of the hood) supposed to close when the engine is started and slowly open after the engine is shut off and the vacuum slowly bleeds away. Also is the vacuum supposed to be fed directly from the manifold or off of a varible vacuum fitting somewhere else. I'm trying to determine if I need to buy a new valve.

As you can tell I've gotten myself pretty confused on how this is supposed to work correctly

Thanks

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Dave Knapp
'70 SS 396


[This message has been edited by DaveK (edited 10-07-99).]

[This message has been edited by DaveK (edited 10-07-99).]

The hood door should be open when the engine is off. On start up it closes smoothly and doesn't open until hard acceleration. The door vacuum actuator port should be connected to a manifold vacuum signal with the check valve in beween. I don't remember which way it goes (and my car isn't at work with me) but you won't hurt anything by trying it both ways.

The vacuum source is located at the same fitting for your power brake metal line. If you're running the factory intake, of course.

Yes Dave, The inline valve is installed with the brass towards the manifold.

Dave, just for your info, there is a check valve available from GM parts that will function just like the Cowl check valve. You can use this valve and save your original or repro to put on when you want to show it. The valve from GM works great and it allows the Cowl door to close a little more slowly than the correct valve, which I like. The one from GM is MUCH cheaper than the repro valve and the part number is 8997639.

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Tom Parsons

Great, Thanks for the tip http://www.chevelles.com/forum/smile.gif I'm going to run down and pick one up.

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Dave Knapp
TC #388
'70 SS 396

[This message has been edited by DaveK (edited 10-14-99).]

[This message has been edited by DaveK (edited 10-14-99).]