Just got back from a friends house, and he has installed a lt1 in a very early customized pickup. The problem is there is a hissing from the tb. Its the two holes in the bottom of the throttle body that are doing it. Where does those hole lead to and what do they do. You can see them when to take the filter off and look at the blades. What can we do to get it to stop hissing?

Thanks for any help.

 

I think you are talking about the coolant inlet/outlet holes. just block them off with 3/8' caps...
im pretty sure thats what your talking about

 

Is it a BBK throttle body? They are notorious for a "whistle" from casting flash in the idle air passages. Those are located at the bottom of the divider wall between the blades.

 

This is exactly where it is comming from. But it is still a stock TB. We never noticed it when the motor was in a different car. Are those just passages that allow air by so the car will idle?

 

I had to drill the hole a little bigger to get the car to idle with the new cam but then i drilled it too big and the car would not drop from a 2000 idle. Mine whistles as well but i think that has something to do with the ram air box...

 

my 58mm edelbrock whistles loudly. I kinda like it though. Been asked so many times if its supercharged. I think with the ram air intake it makes it more noticeable...maybe, maybe not