On the throttle body there are two large holes - one before the throttle plate and one after - that mate up with passages on the intake manifold that are not connected to the manifold plenum. Can someone tell me what these are for?

 

Looking at the Helm manual schematic, it seems to be related to the Idle Air Control system. It allows air to bypass the throttle plate to up the idle speed under cold start conditions.

 

So what would be the results if I make my own gasket and block the hole to the manifold from the intake side of the throttle plate?

 

I would guess that your cold start idle will no longer be controllable. Try this test:
Before the first start of the day, remove the intake tube to expose the throttle body. Plug that first hole with your finger (or a bung or duct tape - just don't let it get sucked into the manifold). Start the car. Does it still go to fast idle like it did before? You should have your answer then.

 

Thanks xviper, I'll give it a try. I'm trying to solve a problem I have with the 600 cc injectors. At high vacuum throttle settings, the slightest let off of the throttle causes the injectors to shut off and the car goes into a gear down mode. I'm thinking the ECU uses these ports, and at a certain vacuum, shuts down the injectors.

 

please let us know what you find.

 

You're getting into uncharted territory for me. Good Luck!

 

[QUOTE]Originally posted by xviper
You're getting into uncharted territory for me.