Author Topic: Backfire/ popping like mad!!...  (Read 2720 times)

Offline blaq71

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Backfire/ popping like mad!!...
« on: November 13, 2012, 07:38:24 PM »
Ive got a 308 with a quadrajet thats backfiring/popping like crazy when idling and idle screws dont seem to make a whole lot of difference. slight popping started after i changed all the vacuum lines and swapped the rocker covers over so the PCV was on the drivers side. slight popping under deceleration and at idle. as i just bought the car and it smelt like it was running real rich i figured a new needle/seat/gaskets and a clean out would fix it, but cleaned out and back on and its worse than ever, continual popping at idle but throughout revs sounds lovely and doesnt smell like fuel as before.. I set the float at 3/16 as per the kit instructions than tried in between 1/4-5/16, 7mm to be exact and it was little better but still popping like mad.
It’s on a 71 HQ Holden, these are the casting numbers located on the carby which don’t seem to match the car.
17045281
2686
17051602 circular casting number.

After reading a few posts i now question is it running too lean on idle rather than too rich as i first thought? hence the intial backfiring after replacing the vacuum lines and changing over the covers. ( would that have even made a difference?) or is it a float level issue or as im new to quadrajets is it something that i got no idea about?? lost and confused :o :o  also it is leaking some fuel from the air horn gasket is this part of a bigger problem??

Offline Cliff Ruggles

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Re: Backfire/ popping like mad!!...
« Reply #1 on: November 16, 2012, 02:10:01 AM »
"Backfiring and popping" is most likely ignition related.  Could be a worn cam lobe, broken/weak valve spring, or other valvetrain related issue as well.

Double check the carburetor part number, should be 1705XXXX not 1704....Cliff