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got 2002 m6 and i want to noe Wat size drill bit for tb butterfly hole. i dint wanna take off/on/off/on the t-body to look for the exact readings. for those guys that have done this mod wat size bit for a 35 reading? thaks in advanced.

Constrictor 98TA

I think I have the general gist of what you're asking, but I drilled mine to 3/16" and it helped a little, however, nothing takes the place of a proper dynotune.

Dave Carney

jyeager

Doesn't that depend on your cam?

CAT3

iTrader: (9)

Yes, it does as well as all other mods as it changes amount of air needed for idle. Also factor in the differences in our cars stock, some make 277hp (my friends SS did, ouch) and some make 324hp stock. There is no One size for this cam, only close. And even then, I am not sure you can get it exactly right as Constrictor said.

Cal

iTrader: (1)

If you drill out the existing hole, I've never heard of anyone needing to go bigger than 1/4 inch. It will depend on which TR cam you are getting, and also what your target idle speed is going to be. I didn't remove my TB even once to drill it; just stuffed a rag under the butterfly and drilled away. I'm running a TR224/114 with a 0.250" hole, 950 rpm idle speed both with and without A/C on. Works good for me.

1320_PERFORMANCE

cal,
i got the TR224/112lsa cam, so wat size drill bit should i go with this cam specs.

Bink

Start with an 1/8" and bump up from there. Use the rag as Cal stated.
joel(Bink)

1320_PERFORMANCE

Thanks guys

Cal

iTrader: (1)

Unless you have a set of number sized drill bits, it's very easy to drill out the stock hole too big. Note that the size joel sugested is smaller than the stock hole size. That's because he's talking about starting a second hole, which is easier. The 0.250" size I was talking about is not for a second hole, but the max for drilling out the stock hole size. Anyway, the generaly accepted procedure is to drill one size at a time, checking your IAC count until it's in the 30s. In my case, I simply drilled until my car idled fast enough with the AC and cooling fans on and the engine hot. With all that stuff off and the engine at full operating temperature, my IACs now go to zero and the idle speed rises to 1000rpm, but I don't have a problem with that. What I'm telling you is you may have to make some compromises because the IAC may not have enough range for your setup.

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Thanks cal ill start of with the 7/32nd drill.

Drew778

iTrader: (2)

Thats what we started with

But since I got the S2 TB, mine is still stock size with the idle rpm's raised to 900 and it still surges once in a while when cold.

The best thing to do is get you idle raised with programming.

Cal

iTrader: (1)

Right, drilling the TB will help the engine maintain the programmed idle speed by letting in more air, but you also need to increase the PCM's target idle speed to something a bit higher with LS1edit. Having too low of an idle with a bigger than stock cam causes several problems. I like 950 rpm with my M6 and underdrive pulley.

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well i drilled my tb butterfly wit 7/32nd and hooked up gm's tech 2 and my iac counts went all the way down to 27 @ idle, well was wondering if thats about right? or can i drill it to the next step(15/64). when i start it up in the morning she starts right up but ones the engines in operating temp and i try and start her up again she surges a little and then starts up and idles fine. and when i finish work today on my way home i turned my a/c on and on a stop light and she died out> so wat do u think cal one more step up? 15/64 is b4 my 1/4 drill bit set. so should i go str8 to 1/4 or 15/64th first. keep in mind my iac counts went all the way down to 27 @ idle and operating temp.

Cal

iTrader: (1)

If your IACs are at 27, then 1/4 inch will probably be too much; go for 15/64, but even that could be too much. That's why I said you should have the number drill bits. Harbor frieght has them pretty cheap. If you go too far, the IAC will go to zero, then the idle will creep up 100 rpm or so. I had to do that to get mine to idle good with the AC on.

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With the 7/32nd my car is idling @ 790 to 810 rpm the desired speed is 800 rpm. Why does my car still surge @ wrm start ups @ times?

Cal

iTrader: (1)

If it only surges @ warm start-ups, sounds like the Main VE table needs to be scaled down some. It could also mean you need to change the IAC decay tables. Try loading these tables with straight 31's just to see what happens . . . you might get some cruise control effect, but it should take care of the surging. If the rpms won't come down, try some smaller numbers.

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Sorry Cal but dont have ls1 edit yet. But when i do get it ill be askin u lots of Questions. Gm's tech 2, is alright to use with ls1 edit?