Help Need Advice!

This is getting old, but….. I changed out the distributor cap and replaced the base gasket on the carburetor and got the engine to run. It ran at about 1000 RPM until I got it up to operating temperature in order to set the idle speed and timing. When I turned off the engine in order to hook up the timing light and tachometer the engine continued to run, then the RPM’s increased. I could swear the engine ran backwards for a few seconds and belched, once again, gas and flames out the carburetor. The engine now runs at about 3000 RPM.

The engine is a 289 with a Holley Street Avenger. Frustrating! All advice will be helpful.

I put the original Holley carburetor back on and problem is solved. I must have blown out something in the Street Avenger when it backfired through the carburetor. Live and learn. Now I have an opportunity to rebuild the new carburetor.