347 stroker
+1y
Sounds like it can POSSIBLY be a vacuum leak... vacuum leaks can tend to have opposing effects... if the vacuum leak is pre-venturi in your carb it will accelerate the engine... if it's post-venturi it will run very poorly or not run at all depending on how big of a leak.
You can test if its a vacuum issue quite easily in your case, since it's running that is... Get some starter fluid, and while the engine is running spray some carefully around the vacuum hoses and carb... try not to get it in the carb directly... If the engine revs up that's a tell-tell sign that it's a vacuum issue. You should be able to isolate where the leak is using this method.
Be careful... don't spray too much, just little bursts at a time because you are already revving pretty high @ 5,500rpm, and if it is in fact a vacuum leak, the you will be increasing your rpm speed every time you spray.
If when you spray around the engine does not change in rpms, then it's safe to say it's not a vacuum leak.