Idle tuning issue

[carnut68]

Holley 950 [830 version]. Engine idles 12-1300 whenever you drop in gear it drops to 800. Go back to park it doesn't go back to idle cleanly.If you just blip the throttle it cleans up. IAB 70, MAB 28, IFR31 lower. Mix screws are 1.5 out very sensitive. T slot exposure is square. Timing 25 @ idle, 34 total. Cam is 271@50. 8 in 5200 convertor. MSD pro billet dist with 6AL box. What is blipping the throttle telling me?

[Markv]

What ignition? I had this on an old HEI. Weights were sticking.

[GTO Geoff]

You need a LOT more idle timing with that size cam, maybe as much as 50*.

[carnut68]

MSD Pro Billet Dist, 6 AL box MSD coil. I went to heavier springs[medium] and seems to have stabilized idle timing out/in gear. I'll just have to experiment with springs. Foot brake @2500 so as long as it's all in there I might be good.

[Ron Gusack]

I think I picked up this trick from Tuner years ago. If you take the weights and bend them in a vise, you can limit the degrees of advance and therefore increase the initial timing. I have a little less cam (262-270), the same ignition as you and similar idle issues. I don't think it's completely timing a timing issue and messing with bypass air helps too.

[RFSPHPbb]

there was a write-up on that either here, or the previous site or Chevelles.com. IIRC it was a trial fit type deal, no definitive measurement. I recall that the guy put a rod thru the hole in the weight to keep it from collapsing during the squeeze process. He was using an oxy-acetylene torch to prep the weights. If I can get a little time later I'll try to locate it.

[hipockets72]

If you were using the light silver springs, they often are not heavy enough to bring the weights back to their starting point properly. The size of your cam, locking out the dist would be best, and the engine will hit the converter harder. Was worth .1 in my 60' with a mild converter running locked out versus a 10 degree bushing and one blue/one thin wire silver spring.

[carnut68]

2 light silver springs made it worse, 1 silver and 1 blue was better, 2 blue really stabilized it. I might experiment with 1 heavy silver and 1 light one.

[Ron Gusack]

[ojh]

I'd question the idle rpm, it is great enough to pull fuel thru the booster to create over-rich so when you blip the throttle you effectively clean it out.