Pop Pop Pop
 

1981 911sc

Pcar runs very well. Except.......
in mornings when I first start up there is a pop pop popping sound coming from the airbox. I don't have a popff valve.
doen't happen after car is running.
What would i look at to see what is causing this?

Tx!john

before you do anything else....get a Pop-off valve ASAP.

A blown air box will cost you over 1 grand to replace....ask me how I know..

ok, i'll get one. Would i then have to close the popoff valve each time it is forced open. also, what would be causing the popping?

TX!john

no, the valve is spring-loaded....once it is forced open from the internal pressure release, it will close by itself due to its built-in spring. see pic below.


http://forums.pelicanparts.com/uploads/pop_off.jpg

i see said the blind man.
so, any idea to make the poppung go away?

hey mr. flat, i dont know too much about these 911 motors, all i know is that they are 2 cycle motors...and that's about it. :)

just get rid of the internal pressure buildup and your popping will go away. this may sound obvious, but the sooner you understand the phenomena and source of the problem, the sooner you will arrive to the solution...good luck