Anyone having an engine shake when in drive only, check the intake gasket.
Check my old posts for more but my gasket fell apart when I pulled the intake/exhaust manifols. That was a REAL fun job, but I did it,so can you.!
Here were my symptoms: smooth idle in park,baadd shake in drive. So bad that the box bounced around.
White spark plugs, indicating lean(lean burn I thought) and really good mileage. One barrel carb I thought.........cool.
Idle mixture screw that did squat(lean,and uneducated about the issuses).
Instant detonation when using "quick start"fluid on that part of the intake,but don't do it often.
Thanks to this forum,I was able to make it run like a good dog, not a bag of dirt.I still call it Clifford though.........it's red.

Geetee150

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I call it Clifford, as in Clifford the Big Red Dog. It runs like a bag of dirt and its as slow as a dog.
This is why I signed up to this forum;to either shoot this dog or make it purr like a kitten

From personal experience, the Australian-made manifold gaskets are great. Everyone likes the Remflex gaskets as well. They can be an improvement over stock. You can spray carb cleaner at possible vacuum leak areas. If the idle increases, there is a leak.

Did it do this before the manifold replacement,and is this a 78 or newer car?

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V8?? We don't need no stink'n V8!!