Built a 17080260 for my camaro, help with idle

[montez27]

First my set up. 70 Camaro, 5 speed, 3.08. 350, 9.8:1, 186 heads, 1.94/1.50 valves, open plenum intake(holley street master), tri-y headers, isky cam 224/224, 480/480 with 1.6 rockers. 12 in vacume. Live in Denver over 5000 feet elevation.

17080260 olds Q-jet, sec modified to open fully(they were restricted to 60% or so)
Carb set up 75/50m Prim jet/rod, M hanger w/cv rods,
Idle down tube .035, I moved the IAB to the airhorn(i know you dont like this).041, Idle restriction .052.
 air bypass .082(added to the base plate)
Idle discharge .0935
   This carb was a huge improvement over my other q-jet. Drivability is much improved, BUT, The idle screws are only 1/2 turn out. What can I change in the idle system that will allow me a little more control??  Is the IAB to small. The throttle blades are only 1 turn of the screw in from seated.
   Would like a suggestion on the idle system and maybe an explanation as to why you think GM changed from the direct to the indirect IAB.
   Thanks for your time.
   Monte

[Cliff Ruggles]

Nothing wrong with moving it to the airhorn, the sizes you have chosen are pretty generous, it would have enough idle fuel for a Pro-Stock engine!

I seldom go past .038" on the idle tubes when the upper IAB's are in the airhorn at .050-.052"......Cliff

[montez27]

Thanks for your input Cliff.
   I thought I was being conservative with the idle system!
   OK I'll go up on the IAB from .041 to .045 or so and see what that does. I dont want to over shoot it.
   By the way, this is really good site and I commend you for your effort. I see that you always are able to take the time to answer members questions.
   Thanks again
   Monte

[Cliff Ruggles]

If the lower IAB is .070", .052" upper IAB, and .035" idle tube and .052-.055" channel restriction, there will still be enough fuel for what you are trying to do.

Are you using the 327/350HP camshaft with 1.6 rockers?.....Cliff

[montez27]

That cam is an Isky 270 mega cam. I have your book ordered and it should be here in the next couple of days. I look forward to reading it. I will contact you with any other questions I have after I read it. I also had the Doug Roe book so it will be an interesting read for sure.
   The Camaro had been idling fine with the .052 IAB. It still smelss rich but not as bad as it did before. Still running great and the responsiveness is fantastic.
   Thanks
   Monte

[Cliff Ruggles]

Something else to check is if the idle mixture screws are fully seated.  I've ran into cases where they did not seat after opening up the holes under the mixtures screws with those later carbs that used the metric threads.

With the baseplate removed, and screws fully seated, spray some brake clean or carb cleaner in thru the fuel supply holes and see if any leaks out past the mixture screws.....Cliff