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JTMoney

  • Karma: +3/-0
460 backfiring through carb
« on: September 09, 2014, 05:21:58 PM »
So last trip out after a long run The motor started backfiring through carb.  Now this is an all of the sudden problem.  I'm suspecting bad gas as I was in a hurry and had to fill up at a suspect gas station.  What would cause this?  Am I on the right track or can there be more to it.  I've never had an issue prior to that day.  If I stay off the secondaries it doesn't do it.  But it now idles a little rougher than before.


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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #1 on: September 10, 2014, 08:29:04 AM »
Any motor guys with any suggestions????


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jimpen

  • Karma: +68/-0
Re: 460 backfiring through carb
« Reply #2 on: September 10, 2014, 08:39:49 AM »
Check you distributor  and make sure it has not moved.  Just a thought.
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  • Boat #1: 18 CP
  • Boat #2: Xcursion 23 RF
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mash on it

  • Karma: +29/-0
Re: 460 backfiring through carb
« Reply #3 on: September 10, 2014, 08:52:36 AM »
Take a good look at your ignition system- carbon tracking in the dizzy cap, leaky plug wires, and possibly a cracked spark plug. Points system? they might be shot or out of adj.
I had a broken rocker, #4 exhaust i think, that did funky things and would barely idle/run (I unhooked #4 wire and ran on 7 cyls. quite well)
A lobe on the cam might be going away, too

'Suspect fuel' might be an issue, more likely water in the fuel, if anything (mine's had 50:1 premix and diesel ran thru it at times and never missed a beat)

It also could be a lean sneeze, which is a different problem all together.

Good luck

Dan'l
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CJ/RR 212...under construction  "Pistol Annie"

MPKardell

  • Karma: +1/-0
Re: 460 backfiring through carb
« Reply #4 on: September 10, 2014, 09:17:53 AM »
Check the simple things first: Fuel filter? Collapsed fuel line?  If it ran lean after the problem started, you might have wiskered a plug, causing a miss/rough idle.
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  • Boat #1: 1991 Dana 22' day cruiser
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gsmitty

  • Karma: +10/-0
Re: 460 backfiring through carb
« Reply #5 on: September 10, 2014, 09:38:45 AM »

Quote from: MPKardell on September 10, 2014, 09:17:53 AM
Check the simple things first: Fuel filter? Collapsed fuel line?  If it ran lean after the problem started, you might have wiskered a plug, causing a miss/rough idle.
also if running a power valve in your carb after sneezing threw the cab that will now be junk!!!


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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #6 on: September 10, 2014, 11:25:18 AM »
Ya  gonna replace all the fuel filters and blow out the lines.  I guess checking the plugs would be a good idea.  Do you guys think that if I dump 10 gallons of av gas in that would help?  Also I have an HEI.  How do I check that?  I don't think it has points?


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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #7 on: September 10, 2014, 11:26:34 AM »

Quote from: gsmitty on September 10, 2014, 09:38:45 AM
also if running a power valve in your carb after sneezing threw the cab that will now be junk!!!


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How do I know if I have a power valve?


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brchris

  • Karma: +2/-0
Re: 460 backfiring through carb
« Reply #8 on: September 10, 2014, 11:30:41 AM »
Hei dont have points. What kinda carb do you have

big river chris

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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #9 on: September 10, 2014, 02:34:19 PM »
Holley 1850-5 vacuum secondaries


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MPKardell

  • Karma: +1/-0
Re: 460 backfiring through carb
« Reply #10 on: September 10, 2014, 02:50:04 PM »
Quote from: JTMoney on September 10, 2014, 11:25:18 AM
Do you guys think that if I dump 10 gallons of av gas in that would help? 

I wouldn't put ANY more fuel in if you think it's questionable.  Siphon a quart from the BOTTOM of the tank to see if you have water.  Bad fuel + good fuel = more bad fuel.

Do you have a fuel pressure gage?
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  • Boat #1: 1991 Dana 22' day cruiser
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gsmitty

  • Karma: +10/-0
Re: 460 backfiring through carb
« Reply #11 on: September 10, 2014, 05:58:47 PM »

Quote from: JTMoney on September 10, 2014, 11:26:34 AM
How do I know if I have a power valve?


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pull the bowl off and you will see it right there most likely you will have one there aren't to many people that don't run it. We just have always plugged are on the race car so just have done this on all my cabs is just a personal preference!! 


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Your Mom

  • Karma: +20/-0
Re: 460 backfiring through carb
« Reply #12 on: September 10, 2014, 06:07:55 PM »
Pull the distributor and ck for a broke roll pin.  It could of broke an turned the gear just a bit...happened to me a few years back. The pin is under a dollar at most hardware stores.
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berkbryan

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #13 on: September 10, 2014, 08:38:03 PM »
A vacuum leak will do it to

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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #14 on: September 23, 2014, 09:44:04 AM »
Just brainstorming as I am headed out to the river Friday to check the boat.  I have a mechanical choke.  Which way would be off.  I never tied it up and maybe I hit a wake and it moved.  Do my symptoms sound like that is a possibility?


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boatsnores

  • Karma: +0/-0
Re: 460 backfiring through carb
« Reply #15 on: September 25, 2014, 06:22:24 PM »
Id remove the choke and the choke flap on the carb and then take it out to be sure. No need for choke anyways.

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SS-201

  • Karma: +0/-0
Re: 460 backfiring through carb
« Reply #16 on: September 27, 2014, 12:11:37 AM »
Backfire thru the carb relates to a exhaust problem somewhere.

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berkbryan

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #17 on: September 27, 2014, 04:18:18 PM »
Quote from: SS-201 on September 27, 2014, 12:11:37 AM
Backfire thru the carb relates to a exhaust problem somewhere.

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back fire thru carb can be many things timing to advanced vacuum leak running to lean ect.

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novajoeyg

  • Karma: +0/-0
Re: 460 backfiring through carb
« Reply #18 on: October 04, 2014, 04:36:49 PM »
Remove valve cover check if any rocker arms are loose possibly took out cam if you have factory front sump oil pan and make hard turns, happened to me 2yr ago
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JTMoney

  • Karma: +3/-0
Re: 460 backfiring through carb
« Reply #19 on: October 05, 2014, 07:11:19 AM »
Well it turned out my float needle was stuck and the o-ring was flat.  Also I think the gas I had was crap.  I drained it and put new gas in and wide open it ran great.  At idle it was running crappy.  And was hard to start like it was flooded. I opened up the float window and gas poured out.  Which made sense. Ripped the bowl off and replaced the needle and seat and it ran great the rest of the weekend.  I'm glad it was a simple fix and I don't have to think about it all winter.


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