Join Date: Mar 2002
Location: Austin, TX, USA
Dennis is right. Check your jetting, choke settings, secondary opening, float levels and power valves. Holley power valves are prone to blow-out if the engine backfires. Some of the newer Holley carbs have blow-out protection which is a tiny check ball in the base plate to protect the power valve. Older Holleys do not. You can buy a kit to install one if that is a problem.
Use the spec sheet to set everything back to baseline and start tweaking from there. One problem with Holleys is that there are so many adjustments that you can get into trouble. Some folks who claim to be carb experts will apply fixes that they had success with on one engine that are totally whacked on another. Starting at the baseline should give you acceptable performance.