I have a BBK dual 58mm TB. I was perusing PCM info one day when I ran across a writeup on split BLMs that talked about a built in "leak" in the aftermarket throttle bodies that shouldn't be there.. anyone know about this. I looked at my throttle body and the back looks exactly like his AS&M where he says it is going into the intake manifold instead of through the idle air passages. He shows how to plug it up so this doesn't happen. Has anyone else done this? Is it necessary, or even preferable? I have my TB off right now for polishing, so I would like to know more info...


Jonota

Info and pic here

 

Have you scanned the PCM to see if you do in fact have split BLM's?

 

I don't have split BLM's as I still have the stock cam, so I don't think that should be an issue. I am concerned that I may have air going where it is not intended. If this is in fact the case, then I will go get the minor parts needed to correct as described in the page... but if it is SUPPOSED to go into the manifold AND through the passage in the bottom of the intake manifold then I will leave it alone..

Jonota

 

A pic of the backside of a stock throttle body would help answer my question. Does anyone have one?

Jonota

 

If you compare these two pics you will notice that on the "stock" unit, the area for the idle air to pass through does not intersect with the main throttle body passages (behind the butterflies), and therefore does not go into the intake manifold through the normal ports. Instead, it enters through the small passageway in between and under the ports on the intake manifold, that presumably is small passages for idle air alone. On the BBK, this area has been connected to the main throttle body passages, and therefore allows air to go into both the main area of the intake manifold, and the idle air control passages...

Is this something I should correct, or not?

stock throttle body rear view

BBK throttle body rear view

 

Interesting post,
The BBK/Edlebrock TBs tend to make this horible sucking noise. I corrected mine somewhat by cleaning up the IAC passages with a dremel but it did not compleatly fix it, just helped a lot. Take a look at the back of the holley in the link below and it is more like the stock unit, it just has a single hole for the IAC that is not connected to the main bores as the BBK is. I now have a Holley and have none of the sucking noise I did with the BBK. I dont know for sure if the passages are the problem but it would be interesting to find out.

http://chevyhiperformance.com/techarticles/68578/

 

Yes, mine makes the sucking noise (I kinda like it) I think I will end up blocking up those passages so that it only goes through the idle air line... I will post more if it changes anything..

Jonota

ps. the reason behind all of this is that when I'm low low rpms driving around, my car kind of surges a little, like I'm in a flat spot between giving it gas and not... so I was checking into this.

 

Anyone? Yea or Nay for closing up the "air short"?

Jonota