PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Drilling 90mm tb for idle

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Old Apr 22, 2007 | 07:42 PM
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Default Drilling 90mm tb for idle

I have a 408 with a fairly large cam and I was told to drill my NW 90mm tb to get the idle better. Is this common or should I try to get it tuned better. Thanks for any help.
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Old Apr 22, 2007 | 08:04 PM
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the hole on the NW is almost smaller than on the stocker, I'd drill if I were you.
I researched the same question a while ago and decided to drill.
Getting a 408 to idle ok without it would be tough I would think.
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Old Apr 23, 2007 | 12:50 AM
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Tune first, then drill. Often times the idle is liveable just through tuning (unless its fly-by-wire). Although if the hole is smaller than stock, it probably wouldn't hurt to enlarge it a little.
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Old Apr 23, 2007 | 04:06 AM
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I cant find it now, but I strictly remember reading a post a few weeks ago saying not to drill tb's anymore

I would search a little more before deciding to drill a perfectly good tb
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Old Apr 23, 2007 | 05:51 AM
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https://ls1tech.com/forums/pcm-diagnostics-tuning/177230-stop-drilling-those-tbs-fix-stalling-without-computer-tuning.html
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Old Apr 23, 2007 | 07:05 AM
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Use the Set Screw on the front of it to open up the Blade a little more to help it. I don't know about the NW, but the Holley 90mm has a screw. I was told not to drill it also.
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Old Apr 23, 2007 | 11:07 AM
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my 408 idles just fine without drilling... also has a very good sized cam in it.


its all in the tune..
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Old Apr 23, 2007 | 11:29 AM
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Well color me wrong I guess.
Just out of curiosity, what is the hangup people have on drilling anyway?
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Old Apr 23, 2007 | 04:14 PM
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I'm not 100% sure, my belief is that its just an unneeded mod. Other tuning and options are available without having to drill a perfectly working TB
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Old Apr 23, 2007 | 04:20 PM
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The way I see it is that if you drill for one cam setup and decide to go back to stock or lesser aggressive cam setup the hole you have drilled is now too big for the new setup, especially if all you have to do is follow the directions in the link that 8a8mfh has posted above, this is the post I remember reading previously.
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Old Apr 24, 2007 | 09:37 PM
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I have a 408 as well with a 264/272 cam and I have the throttle screw all the way in and it barely idles. I was thinking about enlarging the hole as well.
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Old Apr 25, 2007 | 12:20 AM
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I would try and replace that set screw with a longer one first.
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Old Apr 25, 2007 | 09:02 AM
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Originally Posted by fil131
The way I see it is that if you drill for one cam setup and decide to go back to stock or lesser aggressive cam setup the hole you have drilled is now too big for the new setup, especially if all you have to do is follow the directions in the link that 8a8mfh has posted above, this is the post I remember reading previously.
You can still make adjustments in the tune to compensate for a TB hole that is too large. Its the same as adjusting the tune for a TB hole that is too small, just in the opposite direction. The only downside is that there are limitations as to how much you can compensate for, which is why I mentioned to tune first, then drill (if needed).
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Old Apr 26, 2007 | 04:56 AM
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Please step away from the drill!! Traver
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