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Member #804
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5,539 Posts
Discussion Starter #1 (Edited)
putting on speed inc. CAI earlier tonight noticed the throttle body has a hole drilled in it like 17/64th. size. From what i've gathered no previous Gen III TB has that hole drilled in it as its a mod most do after a cam swap. I've been a firm beliver in this RPO LS1 didn't get a revised cam and inherits the same .479/.467 cam vettes and fbodys have. Lutz specifically said changes were made to the camshaft and exhaust amongst 400 changes from monaro to GTO. The hole in the TB and LS6 springs I saw first hand have me curious of what is in our GTO motors.
 

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Can't help ya, Sorry.
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14,481 Posts
Just a question, Still Learning here,

Is the hole there to allow a small amount of air flow during idle? Wouldn't it be simpler to put a stop on the butterfly valve so it does not fully close?
 

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Member #804
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5,539 Posts
Discussion Starter #4 (Edited)
Thanks for clearing things up DY.

Alot of engines use an Idle air control motor PJ, all your doing with drilling a hole opening the throttle some or IAC motor is a controlled vacuum leak. You can have it where throttle plates stay tiny bit open for idle but to compensate for a variety of conditions it would have capability of moving the throttle plate at idle as drive by wire does.

The CAI is good, I found myself shifting at about 4800 instead of 5500 the power I was accustomed to was lower in the rpm. Gained 1-2mpg too.
 

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Knight Errant
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1,800 Posts
Same thing...

The same thing is done on Carbs all the way back to analog days. It's all good...
 

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Member #804
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5,539 Posts
Discussion Starter #8 (Edited)
Blitzu said:
Don't know exactly what this means but it looks like the GTO's have the largest lift cam shaft next to the LS6.

Bascially this...

Intake lift...
3.24 - LS6
2.92 - GTO
2.74 - Vette LS1
2.68 - Trans Am

Exhaust Lift....
3.22 - LS6
2.92 - GTO
2.81 - Vette LS1
2.74 - Trans Am

Wow... I guess that is why these heavy GTO's can still run low 13's... :
Where did you get thoes numbers from???? Y and F bodys with RPO LS1 have the same camshaft 2001 onward. So how could they have differnt lift. GM is a globalizing expert and wouldn't design a individual camshaft for the GTO, did they? or take another camshaft already in production.
 

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Member #804
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5,539 Posts
Discussion Starter #9
Shag Finger said:
My Z06 had that very same hole ;)
I dont' think Fbodys have that hole, my silverado didn't have that hole.

Looks like its time again to remove the valve cover and check lift this time.
 

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Upstairs in the basement
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GMH GTO said:
I dont' think Fbodys have that hole, my silverado didn't have that hole.

Looks like its time again to remove the valve cover and check lift this time.
I just got confirmation from one of my buds who went out to his garage and took a look, yup they have the hole on the Camaro SS version of the LS1 TB as well. :secret:
 

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I have done a lot of tuning with Weber DCOE's -a performance carburettor designed and built in Italy-, also known in the US by small engine tuners in the pre-FI era. As pointed out by one of you, a small hole through the throttle blade is intended to allow for a small amount of air to pass along the intake and lean the idle mixture whenever available idle jet combinations are ineffective. This is often the case when tuning mods include long duration cams or inefficient intake manifolds.

I have not researched the GTO's LS1 to be able to contribute significantly to this thread, however, based upon the same principle albeit in a different setting, the LS1 may only need a minute amount of air to idle correctly.
 
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