1971olds350

hey guys what can cause a lopey shaky idle on a stock olds 350 w/ 180k miles?
im suspecting low compression, bad timing chain, or flat cam lobes
i removed the fuel pump and the timing chain was easy to move

csstrux

Personally I would look at the simple stuff first. Look at the electrical, IE plugs wires cap rotor. a miss will give a lopy idle, and is much cheaper to fix than replacing a cam, or timing gears.

joe_padavano

I'd add vacuum leak to that list.

1971olds350

i changed the intake manifold gaskets, carb base gasket, rebuilt the carb, i also only have two vaccum lines one for the dist from the carb and one for the trans from manifold vaccum, a new fuel pump, stock hei dist, 8.8mm spark plug cables, ac delco plugs. and still a very unstable idle

captjim

OK, troubleshooting 101
With the engine idling, slowly cover the carb with a towel. If the engine picks up and smooths out, vacuum leak.
Unlikely that it is running rich, any black smoke?
Check timing, should be 36-38 total, around 20 or so at idle
Double check the firing order, especially #5 and #7, easy to mix up.
Do a cylinder balance test. Cancel each cylinder, one at a time. If you find a cylinder(s) that when you pull a wire or cancel the cylinder, there is no change, you have a dead one. Pull that plug and look at it. If it and the wire looks good, do a cranking compression check. Get back to us with results.

Redog

^^ I was going to say vacuum leak and mixed up plug wires too

OLD SKL 69

A vacuum gauge will help point you in the right direction. If the motor is healthy, a stock 350 should give you a steady reading range of 16-20. Depending on whether it is a steady low reading or a reading with slow or fast fluctuations can help you pinpoint the cause. Let us know what the results are.