All Holley carbs built since 1992 have power valve protection built in. All Holley clones that I've seen also have this protection. It's nothing more than a ball bearing in the vacuum path that acts as a check valve when the engine backfires. These are great when you need them but can cause their own tuning issues.
Certainly your carb needs some fine tuning but you should not discount the ignition system. You can't go wrong with an MSD Pro Billet unit and a 6AL ignition box.
Check out the Innovative LM1 wideband AF meter. It's a great tool for tuning your carb.
Last edited by pbrown; July 14th, 2007 at 05:38 PM.
Patrick Brown
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