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2016 Scat Pack M6
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Discussion Starter #1
I am looking at picking up a larger throttle for my car, I am also planning on porting the manifold while I am at it as I am setting up to install my nitrous kit. My question is this: is the BBK 90mm throttle a straight through (non "venturi" design) or does it have a taper bore?

In the event it is a taper bore type (BOO!) I will wait and buy a fastman when he starts taking orders again, otherwise I can go with a BBK now even tho it is a slightly more expensive option. As always, thanks in advance guys
 

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I have a 95mm tb. Its straight. Getting ready to put hellcat 92mm tb on it though. Same thing, for the nitrous. I dont have a bbk except the one in the closet thats 85mm spare. My engine is a 5.7 also. Just make sure the butterfly is true 90mm. The taper is bull$hit and a waste of $$. Not a true mm size.
 

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2016 Scat Pack M6
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Discussion Starter #3
I totally agree, adding another choke point in the system by tapering down smaller than advertised does not help performance no matter how much smoke a company wants to blow up gullible people's @$$es.
 

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Ive read numerous posts that say bigger wont do anything. Hell ive got the 95 on a 5.7 and it screams. Others say buy ported. Like thats going to help. Lol. Crazy. Seems like everyone just jumps on a bandwagon and is scared to try anything other than what they read here. Yet youve got LS guys running 102 mm on 5.3's.
 

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2016 Scat Pack M6
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Discussion Starter #5
Anyone who understands the principles behind ITBS knows bigger is better when WOT response is what you are looking for...
996378
my ls7 I am putting together for my other car has 8x 55mm throttle bodies for a 441cid motor...
 

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Exactly. I see we are two peas in a pod. Seems we are about the only ones who beleive/run these set ups. Let the engine breathe. It will take as much air as needed.
Love those independent tbs, nice pic. Ive got a sbc thats 326ci. Big bore/short stroke, long rod 6.2. Its a screamer at 8700 rpm's.
 

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2015 RT Shaker (STP/A8/FORGED/NAPPA/NO SUNROOF)
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2010 R/T Classic 6M
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Venturi is good for carbs, not so good for EFI. Venturi causes negative pressure to suck in the fuel in a carb.
Now a larger throttle body isn't always gonna be better. Going from 80-90 isn't a big deal but throw a 120mm on a little stock 5.7 and you're throwing most of the throttle input out the window because at part throttle the giant TB is already flowing enough CFM to feed the engine at max lift.
I'm not sure of the stock 80mm flow #s but for reference the stock 90mm in the LS3 flows over 1,100 cfm. That means it can support ~750hp. Stock Apache/Eagle heads can support 700hp as well. So I'm gonna say that on an N/A motor, in ALMOST any case, the hemis will not need a bigger throttle body, and any gains you're feeling are just the fact you can make the same power at a lower throttle input.
 

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2016 Scat Pack M6
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Discussion Starter #9
The bigger the throttle surface area, the quicker the manifold will go from vacuum to atmospheric pressure by allowing air in faster. Any restriction which slows airflow down only serves to delay the car's response.

Yes, too big of a throttle will make part throttle act as if it is full throttle making the car more "snappy" however if you want faster response bigger is the way to go. You just have to self modulate more on the street. Most motorcycles run some form of ITBS, either individual carbs or throttles per cylinder, which is why they feel both very responsive and very touchy.
 
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