fastshape

1967 289 Was running fine .. now idles fine until put into gear then extremely rough idle and stalls. Has good spark at all cylinders however 3,4 and 8 show no drop in idle when plug wire is removed. My initial thought is timing chain. As a side note the trans(auto) started acting up at the same time, not shifting into 3rd gear.

kenash

Hi,
OHM all of the wires. Check the cap for tracking. Still running points? Check the Dwell? Check the modulator rubber hose for signs of wear, cracking etc. You could have a vac leak. In fact, check the engine idle vac, while at it. I wouldn't think timing chain at this time.
Good Luck.

fastshape

wires are good, cap is good. have electronic conversion. vac is good.

kenash

So, being "good" it's in the high teens/low 20s? That is, if you're running a stock cam?
Could it be something as simple as the idle dropping off when placed in gear? If so, is the malady you mentioned concerning your C4 causing the drop due to unknown drag in the transmission?
You mentioned no change in engine cadence when you pulled those plug wires (assuming one at a time). As you know, that's a sure indication of dead cyl., that is, if the wire was completely removed from the plug? There should have been a change.

Al Newman

The vacuum line running from your intake manifold down to the passenger's side of the transmission is your culprit. There is a rubber line bent in a really tight horseshoe shape that attaches to the transmission that undoubtedly needs replacing, either because it has split or it has softened up to the point it no longer seals on the valve's nipple. That will cause both of your symptoms. Otherwsie, check the seal at the intake for an air leak. The problem is most likely vacuum related.
Best,
Al

fastbackford351

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jlg2002

I have also seen a bad power booster (leaking vacuum) affect the rear cylinders as well.