Why does the bbk 52mm throttle body have a upper hole above the iac passage that goes nowhere? It just dead ends into plenum.

 

I don't have a picture in front of me but its likely a casting gate, vent or tool pick out.

 

Example pic : Top port goes to nothing

 

Upper passage goes to large side port on the Throttlebody. Pcv vent hose

 

hole goes straight thru throttle body and sealed by the gasket at back, does that port come in from the side of that passage?

 

If you have a hole straight through the Throttlebody that’s a major potential vacuum leak if the gasket isn’t sealing it.

 

it's straight from factory, new. odd right? I could see if it turned into that side port but it's drilled straight out the back

 

If this is an old bbk take off the cover. Pretty obvious where the port goes. This is for crankcase vent and yes the passage goes out the right side of the tb.

 

straight through would be a problem unless it taps into the iac passage but still shouldn’t be able to see straight through the tb.

 

not an old one doesn't have a cover

 

it definitely machined with intent to go thru. Although it serves no purpose

 

That’s a huge vacuum leak, I’d call bbk and inquire. Could be defective

 

Should just look like this with iac and ported vacuums passage only.

 

yes, that hole on bottom is thru.
I just had to run outside to take mine apart again to double check it is teed in the pvc passage but goes thru entire body

 

yes, that hole on bottom is thru.
I just had to run outside to take mine apart again to double check it is teed in the pvc passage but goes thru entire body

 

it does not seem to leak as the gasket is behind it and solid metal of plenum behind that.

 

That shouldn’t be a issue once installed

 

Interesting, don't feel like digging mine out atm but I'll prob epoxy it up when I smooth things out. Hate how they leave things so rough on the newer version but I got a good deal on it.

Casting was used for LT's and maybe other apps, so all could get the same basic machining.

edit: LOL actually just remembered that I bought some stuff to deal with that hole already, Think I got some alum bar stock and was gonna green loctite it in. Funny how I forgot bout that, it's been a few years since I looked it over But now I deff rem planing to fill it. Time flies!