Thread: 350 aggresive surging in gear with moderate throttle.

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if that does not work out, does it have a solid mount or clam shell type motor mounts? if clam shell mounts maybe when the motor twists under load it is shorting out something somewhere. let us know when you figure it out, i am curios what the outcome is.

You installed a bigger pump/gas line for the 350?

How old is this 350? Could it be a worn out and stretched timing chain?

Maybe a broken vacuum hose to the distributor? Would be the easiest guess, sometimes it's the little things... I had exactly your problem and traced it to a cracked hose. you wouldn't even see the crack, but the moment you rev suddenly higher, vacuum gets higher fast (if your on ported vac), that's enough to drag a bit of air through the crack, f**k up your timing and get the engine into low revs again. when revving low the whole game starts over...
JMO, Max