martsink

I was just curious what purpose the bypass hole serves in the throttle body (top left). Is this for idle? My project requires that I mount the TB away from the intake due to clearance issues, so I'm just wondering what I can do about this hole.

The Wrench

The hole is for the inlet air for the PCV system. Note it ties into the metal tube just above it, and runs to a rubber hose that goes into the valve cover. It has nothing to do with the idle system. Under normal, high vacuum operation, it sucks in air to circulate thru the crankcase and then thru the PCV orifice. Under WOT it allows crankcase pressure to reverse and flow into the throttle body and be digested by the engine.
When Mark Shaner ported my TB he left the hole, but epoxied in and smoothed around it so it had less disturbance on the air flowing into the intake manifold.

DG

martsink

Thanks for your reply. Yesterday I realised that I was looking at it all wrong, I thought the hole goes straight into the manifold intake, but it actually going into the sealed off section, so all the air goes through the crankcase tube. I definitely agree with smoothing it out, that sharp edge doesnt look like it helps with airflow

Bill Curlee

Heres a pic of a Shaner ported TB with the modded inlet hole:






You can also block off the water circulation hoses that feed hot coolant into the TB. The engine doesn't need it. The C6 TB doesn't have it either.

I guess if you live in Antarctica, you may need it!!!

Bill

martsink

Wow, that some impressive workmanship

strand rider

Thanks for the pictures, good to see how it is done well.

If I ever get stuck on a desert island with my throttle body in hand, now I will have something productive to do.

The info about the water channels was also appreciated.