99hatchR

i know this might not be a good site for 350 motor but werth a try mods:all stock besides intake manifold and msd dizzy...(?)when the car is running and once you cut off the car it pops(basically backfire)what issue might cause that?? ..car has no issueswhen running only when cut off....another thing that might be included is when your adjusting the timing(timing light) with the adv vac dissconnected to lets say 20 once when you reconnect it ..it jumps to 40 without even touching the gas pedal!

Dough_Boy.

is it carbeurated or fuel injected

actionpaintball

It's running rich and/or the timing is messed up (best guess with the info provided).

Want to get to the bottom of it? Do a compression check on all 8 cylinders (if OK), then re-time, then adjust your fuel delivery. Check for vacuum leaks.

M▲dh▲tter

pretty much the same thing I was going to say,
OP just a rule of thumb, pulling the plugs most of the tiome give you a pretty good idea of what is going wrong and where to start.

Fabrik8

You can also buy a wideband O2 sensor gauge/display and weld a bung in the exhaust for it. That's the most expensive route obviously (usually $200 or more), but it's a hell of a lot better than trying to read plugs or simply guess about what is actually going on. Even though you're using a carb, you can still take advantage of modern things to diagnose and tune.

At least I'm assuming it's carb'd...? It would be nice if the OP responded in his own thread...

M▲dh▲tter

^ Truths...
found an innovate LC1 DB or DR for $166.00
http://streetrays.com/store/index.ph...oduct_id=33722

Also, I like having an EGT gauge for a little more info as well.

audiophile24

Maybe the sphincter valve is too tight?