Jon A

I wasn't talking about the aftermarket TB's. I was talking about the GM LT1 TB and the GM LT1 manifold. If those weren't designed for an LT1, I don't know what was.

The above is how well (or not) the stock system works, with stock everything including TB and cam.

I agree the aftermarket TB makers could have done a better job in this area. I'm just saying it's not like you're throwing paint on the Mona Lisa or something as the factory IAC passage scheme doesn't work all that well anyway, so you aren't losing much. In my case it's unnoticable.

sweetride45

I looked closer at the intake and the TB, and now I can see exactly what you mean by the "IAC circuit"...I'll make something better to seal the TB to the IAC hole on the intake. Hopefully, once my engine setup is done, this should work flawlessly.

My only other question is...why would you need to drill a hole thru the TB and the IAC port? Some sites say you gotta do that. I'm thinking they are just trying to mimick the stock TB. It seems to me that, if you dill the hole, your bypassing the IAC function, having a designated air path to the intake. Drilling the hole makes air ALWAYS go thru, and not so much "controlled" by the IAC...

arnie

In your case, you don't need to. The entrance for the air that the IAC solenoid valve meters is between and below the throttle bores. The one referenced link is using a BBK TB as a model. That TB did not have any hole to begin with, so drilling was necessary. The AS&M already has a hole in that location.
They had better 'mimick' the oem TB. That hole is the entrance for the air that the IAC valve regulates, as noted above. (BTW, that hole needs to be large enuf to not be a restriction.) You are not bypassing the IAC circuit as the air supply originates from outside (bypassing) the throttle plates. Those that have drilled holes into the throttle plates themselves, are the ones bypassing the IAC circuit, as the idle air is now originating from the intake plenum. For the idle air to go thru the correct IAC circuit, the throttle plates need to remain closed and sealed. The air must then flow thru that hole between and below the plates, thru the IAC valve, and then thru the cast/drilled passages in the intake manifold/plenum.

sweetride45

I'm not sure you know what hole I was talking about Arnie. I think I know the hole YOUR referring to, and I agree, both stock AND my AS&M have that hole.

http://web.camaross.com/forums/showt...light=IAC+hole

That link is a better reference I think. It's an additional hole that is drilled thru the front and back of the TB where the IAC passage is. It's about 3/32" in diameter.

Knowing what I'm referring to, is that what YOU were referring to? If not, do I need THAT hole as well?

arnie

Same hole. As I described it's location above; between and below the throttle plates.

sweetride45

So I don't need to do that...only make the connection between the TB and the IAC "circuit"?

arnie

Correct!

sweetride45

Sounds good to ME! I have the holes ported now...once I get back around to it, I'm gonna fabricate a better way to make that "Connection"

Thanks to everyone!

adamz28

So I took the plunge and drilled out my AS&M 58mm TB earlier today. I used a .5 in copper pipe just like described earlier and sealed the hole I drilled from the TB to the port in intake. I could not be more please with the improvement in idle! My car had a terrible idle before this mod. This made a night and day difference.

One word of advice, when doing this mod use a trimmed GM gasket instead of an AS&M. The AS&M does not have the material in place to seal the copper tube to the intake the way the GM gasket does. Not sure if the metal to metal interface would leak with the AS&M, but after going through the trouble of everything else, why take the chance.

Thanks!

sweetride45

I used a 58mm Holley Gasket that worked PERFECT w/ some trimming...also, I didn't drill the bleed hole but made the copper connection and aluminum "seal" piece, and the thing works PERFECT...IAC is in the upper 30's mid 40's on idle and couldn't be better!

Munson

Could this also be the problem with my 54mm as&m? Ive been having idle problems since i put this thing on! but ive also gotten all sorts of random codes too