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Random Backfire
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robins44
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Joined: 29 Dec 2007
Posts: 632

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PostPosted: Tue Jul 16, 2013 1:16 am    Post subject: Random Backfire Reply with quote

Finally got the 383 running again after sitting for two years. Installed a set of hooker super comp headers, and currently running them open. Pulled all the plugs out and cleaned them, and added 5 gallons of fresh fuel to the little bit of fuel I had in the tank. Changed the oil and fired it up. She started right up after I pumped the carb two times and squirted some brown nasty fuel down into the intake. Idles nice and sounds good, but im getting some really loud knarly backfires out the exhaust. They seem to be random. I triple checked to make sure no plug wires were crossed. I ordered up some fresh plugs and I have a fresh carb to throw on. Anything else I should check? Could it be the open headers???? Engine runs smooth and doesn't miss, just has that backfire (throws flames out headers). Could it be the old fuel????


Thanks


Cody
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10sec.et
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Joined: 29 Mar 2006
Posts: 3473
Location: Houston,Texas
346658.74 points


1969 Oldsmobile Cutlass

PostPosted: Tue Jul 16, 2013 1:17 pm    Post subject: Reply with quote

misfire, flooding, slow timing.
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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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af2
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Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Tue Jul 16, 2013 7:17 pm    Post subject: Reply with quote

10sec.et wrote:
misfire, flooding, slow timing.


And crappy gas..
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Tue Jul 16, 2013 9:11 pm    Post subject: Reply with quote

My money is fresh plugs will solve it. Every time I've seen random popping or backfiring in the exhaust it has been a fouled plug (from flooding and crappy gas as previously mentioned). Clay
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I have done so much with so little for so long, I can now do anything with nothing.
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af2
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Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Tue Jul 16, 2013 11:42 pm    Post subject: Reply with quote

clay wrote:
My money is fresh plugs will solve it. Every time I've seen random popping or backfiring in the exhaust it has been a fouled plug


yes and from crappy gas.. Laughing
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squeeezer
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Joined: 02 Mar 2007
Posts: 2427
Location: new richmond WI
191524.76 points


1991 Chevrolet Camaro

PostPosted: Wed Jul 17, 2013 10:38 am    Post subject: Reply with quote

how ya gonna get the crappy gas out???
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robins44
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PostPosted: Wed Jul 17, 2013 1:06 pm    Post subject: Reply with quote

plumbing a new fuel system, so that will be a good time to get all the "crappy" gas out.

Thanks guys for the help.
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89Gmcsierra
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Joined: 28 Oct 2012
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Location: Hazleton, Iowa
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PostPosted: Wed Jul 17, 2013 11:59 pm    Post subject: Reply with quote

I have done an expensive thing to car with Varnished gas. just filled the rest of the tank with 110 octane and ran it dry then changed fuel filters and it was golden afterwards.
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Big Dave
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Location: Tampa Florida
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PostPosted: Thu Jul 18, 2013 4:33 am    Post subject: Reply with quote

That is because 110 gas contains about 40% Toluene by weight. It would be cheaper to just add a gallon or two of lacquer thinner that is 33% Toluene, and 5% Xylene to clean out the varnish.

Big Dave
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Paul P
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Joined: 15 Aug 2002
Posts: 2403
Location: Townsend, Mass.
81572.74 points


1971 Chevrolet Chevelle

PostPosted: Thu Jul 18, 2013 12:20 pm    Post subject: Reply with quote

Too Rich a mixture. I had a backfire issue with the old Pro-Jection and changed out the valve springs and all tune up items to find out that it was a bad tach signal feeding the Pro-Jection dumping too much fuel mix in mid to upper rpm range ( POP-POP-POP). I guess tune up is where to start but it might be a tad rich.
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2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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robins44
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PostPosted: Thu Jul 18, 2013 1:38 pm    Post subject: Reply with quote

No popping or backfires when I put it away. So I'm assuming the jetting is okay.
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Paul P
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Location: Townsend, Mass.
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1971 Chevrolet Chevelle

PostPosted: Thu Jul 18, 2013 2:55 pm    Post subject: Reply with quote

Maybe it is like an STD just give it a while to incubate and it comes around. Laughing
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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af2
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Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Thu Jul 18, 2013 5:41 pm    Post subject: Reply with quote

Big Dave wrote:
That is because 110 gas contains about 40% Toluene by weight. It would be cheaper to just add a gallon or two of lacquer thinner that is 33% Toluene, and 5% Xylene to clean out the varnish.

Big Dave


Dave, So called lacquer thinner in California is Acetone now, just so you know. It is marked lacquer thinner. Then the ingredients say ASSSSSATONE........ Brilliant advertising.. Way worse on the human body than lacquer ever was.
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Paul P
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Joined: 15 Aug 2002
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Location: Townsend, Mass.
81572.74 points


1971 Chevrolet Chevelle

PostPosted: Sat Jul 20, 2013 12:15 am    Post subject: Reply with quote

I wish my girls would use less of whatever is in their nail polish and remover. It is worse than my shop sometimes when I check on them. Rolling Eyes

Sorry wayyyyyy off topic now.

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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af2
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Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Sat Jul 20, 2013 12:28 am    Post subject: Reply with quote

Paul P wrote:
I wish my girls would use less of whatever is in their nail polish and remover. It is worse than my shop sometimes when I check on them. Rolling Eyes

Sorry wayyyyyy off topic now.


Not off topic at all Paul.... Kind of rhymes.. Look up acetone and you will crap!
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