Re: IML: Misfiring/backfiring...

["Stevan Miner" <miner@xxxxxxxxxxx>]

Hi John,
At the risk of sounding over simple-are you sure there isn't a couple plug 
wires mixed around? It's pretty easy to do on a big block Mopar. # 5 and #7 
are common ones that we see get switched.
Steve Miner
Miner Auto Service
Winnebago, MN
----- Original Message ----- 
From: <commenace@xxxxxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Monday, August 08, 2005 11:33 AM
Subject: IML: Misfiring/backfiring...


> Just put about 500 miles on my new 440. So it was time for a major 
> tune-up. On my way to my friend's work (he's a very gifted Mopar mechanic) 
> the engine starting bogging. Misfiring and backfiring out of the tailpipe. 
> After the tune-up, new plug wires, plugs, timing set, carb tuning, we 
> noticed it was "missing" as in running roughly as if a plug was not 
> firing. All plugs were firing, but we were still "missing." My mechanic 
> theorized I might have an intake manifold leak. I tested it by spraying 
> starting fluid where the intake manifold meets the heads. It seemed I did 
> have a vacuum leak.
>
> I replaced the intake manifold gaskets using aviation gasket sealer (good 
> stuff!). Started her up yesterday... Guess what? Still backfiring! I don't 
> really feel it misfiring. It seems that all the plugs are firing, but it 
> is backfiring. It should be noted that on one particular backfire, my 
> muffler exploded. This was completely my fault, I won't get into how, just 
> trust me, it was my fault. As such, without a muffler, the engine, 
> obviously feels rough. Therefore it's hard to judge whether or not it's 
> running smoothly.
>
> My qusetion (at last!) is: what other problems would cause a backfire out 
> the tailpipe (as opposed to in the carb)? Could the timing be too 
> advanced/retarded? Would that cause a backfire?
>
> Any suggestions would be greatly appreciated...
>
> John.
> 1965 Le Baron.
>
>
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