I have an Edelbrock Performer intake on my 355... I have a Holley 650 carb on it... One of the manifold studs was stripped, so i replaced it... I was told to take this half inched plate out because they seem to fool the carb and because I didnt need it... I think its an adapter plate... Anyways.. When I took the plate off, the carb wasnt able to drop right down because of bolt with plastic ports on it coming on of the intake... Its located right behind the carb and right infront of the distributor..... I asked someone about this and they said its a thermo vacuum switch? It was screwed into the manifold but it had a hose coming from one port to the other port, which is plugging it... So i dont think its being used for anything... The guy told me I didnt need it, so I took it out and plugged it with a bolt plug I bought from Canadian Tire... So now the carb goes down all the way... Well when I start my car, my idle is at like 4 grand.... Its crazy... I hear a loud whistling.. I checked all the vacuum lines and everything and its all hooked up right.... No leaks... There is air blowing out of where the 4 barrels are which is whut i think is hissing... It wasnt doing this before, whut could this be? I tried screwing with all the mixtures and the timing... I got the idle down if I switch the timing but it runs like **** and the hissing is loud as hell..... Do I even need to plug that hole in the back of the intake manifold? When u buy the performer intake new, there is nothing in that hole... Im stumped anyone know?

 

There is a square flange carb plate (holley flanged)
about 1/8" thick that comes with a performer manifold
This plate is nessessary to bolt a holley on a performer manifold
You can get it from Edelbrock. Canadian Tire can order you one.

www.edelbrock.com

 

Sounds like you got yourself a major vacuum leak to me.

 

Yea I found out that without this holley flanged plate, its like setting yer carb ontop of the manifold without bolting it down and trying to drive the car..... LMFAO! So yes, tomorrow when stores are open, I'll grab tha ****... Thanks for the info...