Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

17056240 Lean(?) at Idle

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TommyK:
I have found that manifold vacuum can make for an unstable idle due to vacuum fluctuations which make the timing wander. This is especially evident with a cam that has some lope to it.

Have you tried experimenting with ported vacuum and different initial timing settings? Might be worth a try if you haven't.

If playing with the initial timing and switching the vacuum source have no effect perhaps it is time to add a little more idle fuel by opening up the tube, down channel or both.

Rhett:
I already did open the ICR and idle fuel up some  -  what what would be the next to try? ICR to .057-.060?

Vacuum and timing arent making a big difference - the vacuum advance is so limited that it barely speeds up the idle...

Cliff Ruggles:
Too much timing at idle will make idle tuning difficult.  Some engines just don't want or like that much timing.  I'd try a lower initial timing setting and use ported vacuum to the distributor.

My 455 idles a bit "quirky" with manifold vacuum to the advance, even though it only adds 10 degrees. It's smoother and more "stable" in and out of gear without the additional timing....Cliff

Rhett:
Been considering that too, but if I go any lower on timing it just wont hardly run, even when I do connect the vacuum advance.

I thought 20 would be too much initial, but it still revs quick with no detonation. I keep thinking I have some kind of intermittant vacuum leak, but it'll slow right down if I start covering the intake.

One thing I will have to do is get the distributor on a machine - I know total timing and I know when it's in by, but for all I know it could already be coming in at idle. I used the stock springs, but who the hell knows?

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