When did Holley start installing power valve protector valves in all carbs? I have a nearly new 80508S...shouldn't it have a protector valve?

Reason I ask is because I had a severe case of dieseling after shutdown and now the car runs terrible, I'm thinking it popped a power valve but I've never heard of a power valve failing with anything less than a hard backfire.

Anybody have one fail after dieseling on shutdown?

You know the check balance system went into those things sometime in the mid 90's. I remember when I blew them regulalry on my 3310 series one. Yet what you got doesn't sound like blown power valve, but rather poor gas or vapor lock!

Mike

I believe your holley has PV protection & that a blown one is not your issue. Check by let your warmed up eng idle & turn idle mixture screws all the way in. If it DOESN'T die the PV IS leaking.(assuming that your throttle isn't opened so far that you are into the transition slots of the carb which would make this test invalid)

This is going to be one of those head scratchers. It ran perfect before the dieseling incident and terrible ever since.

I pulled the carb apart, checked the PV and it's OK, checked for blown gaskets, etc. and found nothing out of the ordinary. Put it back together and it still runs like crap; swapped on a spare 3310 and it runs perfect again so the 80508 carb is the problem but what could have happened during the dieseling incident to screw up the carb?

John. Could your timing chain have "jumped" when it was dieseling?

OOPS, sorry, looks like you swaped out carbs, in your troubleshooting.

Timing is right where it was and the carb swap cured the problem so the 80508 carb is the culprit.