Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Holley off idle backfire problem
View Single Post
  #30 (permalink)  
Old 05-22-2013, 01:19 PM
eric32 eric32 is offline
Registered User
Last photo:
Join Date: May 2008
Location: ohio
Posts: 2,671
Wiki Edits: 0

Thanks: 143
Thanked 262 Times in 243 Posts
All right guys here is the final results. I went down to a .028 shooter and the backfire still happened so in order to rule things out as it no being enough I put a .037 shooter on and that still did not get rid of the backfire and it hurt throttle response as at that point it was getting too much shot.

Best results for throttle response is with the stock .031 shooter so that is what I put back on and it give a nice clean crisp throttle response. Now the backfire problem does not happen all the time just at certain times. I reved the throttle once and just barely touching the throttle it backfired in park so I don't know what else to check on this damn thing.

Shooter size is not the issue as nothing gets rid of it and I opened up my idle feed restriction on the primary block to .033 from .031. This is a older block and checking the new one I just got its .031 already so I did not make too much of a change to it and now hooking up my vacuum gauge my idle is a lot more stable since its not so lean and the idle mixture screws are at 1 1/8 turn out and I also checked my float level and they are at the half way point on the glass window so they are good.

Everything had checked out ok and I don't know what else to do with the dang thing. It runs very strong on 2000 and up and also cruises very good and idles good just the occasional backfire if you hit it really fast and hard. Even unhooked the pcv valve to hook up my vacuum gauge and did not make any difference so I know it is not an issue.

One interesting thing I tried is I put a towel over top the primary and the engine died so could that mean anything? Doing it by hand does not do anything.

Its had so many backfires it looks like a cannon that was shot. I checked the power valve and its still good.

Holley was no help and looking through all my books I did all the checking and tricks and don't know what else to do. Might take it totally apart and pull the base plate off and check for any casting flaws as I read someone had a off idle stumble but no backfire problem and he finally took his carb apart and he had casting flash in the throttle plate keeping the mixture almost blocked off but still run. O well back to the drawing board. Thanks folks for input.
Reply With Quote