RPMs rise and hold at ~2200 unless I'm stopped.

[JakeRobb]

To add to what everyone else has been saying after getting the idle air figured out you will also want to make sure all your spark advance tables, high and low octane and the idle park/neutral and idle in gear spark tables all kinda "mesh" nicely together, you want your idle table to lead into your main spark tables to make the transition is as smooth as possible

At the moment, the spark tables are entirely factory -- I haven't touched them yet. So while I'm sure there's some tuning to be done in there, I think there should not be a problem with smooth transitions.

Now, if you tell me that my modifications (medium cam, lots more airflow than stock) won't play nice with stock LS1 spark tables, that'd be a different story.

[JakeRobb]

Have some time to work on it this evening for the first time in a while! I decided to continue giving the cheap TB a shot, just to gain some experience before I sign myself up to drill holes in a $4-500 throttle.

I adjusted my throttle stop back to where it was out of the box, and of course the car stalled immediately due to lack of air. So I opened it back up a bit and let the car idle for a while until it was up to temp. Then I sloooowly adjusted it back again, but the car still stalled (though not as soon). It was stalling when the TPS read 2%, which of course meant IAC wasn't coming into the picture. So I opened it back up again, then did a TPS reset. Started the car and got a 1100rpm idle with 0.4% throttle, IAC around 90. Then I backed off the throttle stop slowly, until the blade was fully closed. The car continued to idle, and IAC showed ~130. Time to drill!

So I popped the TB off the car. I was expecting there to be a small hole from the factory, but there isn't one that I can see. It should be right on the throttle blade, right? Does it matter where I drill? I skimmed YouTube a bit and found only a couple people drilling their factory throttles; somehow I found not a single video of anyone doing this to an aftermarket TB.

Anyway, I don't want to screw something up I can't undo. I'm supposed to drill right into the plate? Horizontally, I think I'll go with centered. Vertically, I feel like I could justify pretty much anywhere so long as it's not in contact with the pivot arm and not right at the edge. Leaning towards the midpoint between the bottom of the blade and the pivot. Is this okay? Is there any reason to do something different?

I'm shocked that I couldn't find an existing answer to this somewhere. I'll keep searching while I await a response. Thanks!

[JakeRobb]

I figured YouTube would be a good source, but no. Google Image Search showed me tons of examples. Seems like pretty much everybody does it horizontally centered, and vertically centered in one half or the other (halfway from the pivot arm to the edge in either direction). BRB, going to go drill a hole...

[bk2life]

I figured YouTube would be a good source..

factory GM puts it here

20240806_161442.jpg

[JakeRobb]

3/32" hole: IACs down from ~130->~120.

5/32" hole (~3x the area): ~117. Hardly any change.

What?

[Alvin]

Have some time to work on it this evening for the first time in a while! I decided to continue giving the cheap TB a shot, just to gain some experience before I sign myself up to drill holes in a $4-500 throttle.

I adjusted my throttle stop back to where it was out of the box, and of course the car stalled immediately due to lack of air. So I opened it back up a bit and let the car idle for a while until it was up to temp. Then I sloooowly adjusted it back again, but the car still stalled (though not as soon). It was stalling when the TPS read 2%, which of course meant IAC wasn't coming into the picture. So I opened it back up again, then did a TPS reset. Started the car and got a 1100rpm idle with 0.4% throttle, IAC around 90. Then I backed off the throttle stop slowly, until the blade was fully closed. The car continued to idle, and IAC showed ~130. Time to drill!

So I popped the TB off the car. I was expecting there to be a small hole from the factory, but there isn't one that I can see. It should be right on the throttle blade, right? Does it matter where I drill? I skimmed YouTube a bit and found only a couple people drilling their factory throttles; somehow I found not a single video of anyone doing this to an aftermarket TB.

Anyway, I don't want to screw something up I can't undo. I'm supposed to drill right into the plate? Horizontally, I think I'll go with centered. Vertically, I feel like I could justify pretty much anywhere so long as it's not in contact with the pivot arm and not right at the edge. Leaning towards the midpoint between the bottom of the blade and the pivot. Is this okay? Is there any reason to do something different?

I'm shocked that I couldn't find an existing answer to this somewhere. I'll keep searching while I await a response. Thanks!

Aftermarket throttle bodies often do not come with a hole. A big mistake.. The plate and bore are often made of different materials so that gap is different as it warms up. You can add a hole. Just start small. Typically in the lower hemisphere.

The IAC passages also usually suck on most aftermarket throttle bodies. I run into situations all the time with them were the engine is at 300 counts cold and 0 warm because there is just not enough airflow range in that passage. I only recommend NW throttle bodies.

This also explains the sticking TPS. The throttle stop should be set so that the blade doesn't hit the bore when closed. That is it's function.

In all honestly most aftermarket throttle bodes are a hot mess of garbage.

[JakeRobb]

Typically in the lower hemisphere.

I went with the upper half because there's a big "92mm" in the lower half and putting a hole there would look silly. Not that anyone ever sees it but me.

One advantage I would have had going with the lower half is that the throttle blade wouldn't have tended to deflect as I pressed down with the drill. A lesson for the eventual nicer TB, although I suppose I could just flip it over and drill from the back....

The IAC passages also usually suck on most aftermarket throttle bodies. I run into situations all the time with them were the engine is at 300 counts cold and 0 warm because there is just not enough airflow range in that passage. I only recommend NW throttle bodies.

That doesn't appear to be a problem with this model yet, but time will tell. It has yet to see an IAT below 80 degrees.

I plan to get a NW when I get around to replacing this one. (FWIW I've heard that Katech TBs are just rebranded NW models, but they only sell DBW types so it's not relevant to me at the moment.)

This also explains the sticking TPS. The throttle stop should be set so that the blade doesn't hit the bore when closed. That is it's function.

I've done a bunch of reading in the last day or so, and one thing I saw somewhere was that you can use the throttle stop to fine tune the baseline warm idle IAC once you get it in the ballpark with a drilled hole. Thoughts?

In all honestly most aftermarket throttle bodes are a hot mess of garbage.

Yeah, I should have done more research before I bought this one. But for $99 including OEM sensors, I just couldn't not try it, especially since I sold my factory sensors with the original engine.

[2xLS1]

The problem with a lot of A/M throttle bodies is how the iAC passage way and seat is engineered, not just what sensors or IAC is used on it. And if it really was $99 I doubt they are actually GM OEM sensors.

[JakeRobb]

The problem with a lot of A/M throttle bodies is how the iAC passage way and seat is engineered, not just what sensors or IAC is used on it. And if it really was $99 I doubt they are actually GM OEM sensors.

Yeah, fair. Maybe it was a lie.

Anyway, I'm looking at this NW92 from Summit for $399. It says it's compatible with FAST and other aftermarket intakes. Is there any reason it wouldn't work with a factory LS3 intake manifold?