Author Topic: Idle adjustment  (Read 374 times)

Offline Chuck466

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Idle adjustment
« on: April 28, 2022, 07:14:31 AM »
So after getting my timing where I want to start at my idle seems a little higher then I want it, it's around 1800 and I want to idle it down to 1500 on the big and ugly when I make that adjustment should anything else be checked? I read somewhere a while back to use a feeler gauge in the center butterfly should be .004 to .007, just wonder why is that so important?
1990 GMC S-15,  TBS HH 87-1 billet blower, SBC 410ci, Coan turbo 400 5500 stall, Mark williams 9".  3350lbs

Offline JEFF/21C

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Re: Idle adjustment
« Reply #1 on: April 28, 2022, 07:42:35 AM »
Just think of the butterfly as a big controlled air leak the wider they are open the more fuel is required the higher the rpm. Your rpm depends on ign timing at idle if you set the timing at 28* at full advance with a locked dist. is different than having option of advance curve where you can set your intial timing lower rpm will come down

Offline Chuck466

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Re: Idle adjustment
« Reply #2 on: April 28, 2022, 07:53:02 AM »
That's where I have it set at 29deg. locked and the idle is at 1800, so as long as the opening is with in the .004 to .007 at 1500 rpm I should be good?
1990 GMC S-15,  TBS HH 87-1 billet blower, SBC 410ci, Coan turbo 400 5500 stall, Mark williams 9".  3350lbs

Offline Paul New

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Re: Idle adjustment
« Reply #3 on: April 29, 2022, 09:17:10 AM »
1500 RPM’s how big of butterflies do you have in that Big Ugly?  It may be hard to get that low