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Topic: Fire in the hole!!

in Forum: C3 Engines


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Fire in the hole!! (1/12)
 7/27/15 9:15pm
kbrin
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coral springs, FL - USA

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I just had my second carb fire. It seems if my 81 350 L81 doesnt start after 6-8 rotations it lights up in the throat on the second attempt. I just put a new long block with all edelbrock intake and carb. The engine also has a intermittent stumble at 3000 rpm. any ideas?? I am getting tired of replacing KN air cleaners!!

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Re: Fire in the hole!! (2/12)
 7/28/15 12:46am
johnu
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http://www.ehow.com/how-does_5012996_causes-fire-through-carburetor.html

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Re: Fire in the hole!! (3/12)
 7/28/15 12:58pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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Check your timing first. Then check the cap and rotor for a cross-fire inside the cap. New or not, it can happen.
Most likely problem is the carb itself as far as the stumble, but a carb with a vacuum leak can also cause a misfire.
Does it pop and spit back out thru the intake when this happens?


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Re: Fire in the hole!! (4/12)
 7/29/15 6:41pm
kbrin
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coral springs, FL - USA

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Thanks, good info. I will check cap,rotor etc. I don't notice any spitting or popping from the intake but have recently noticed exhaust backfiring.

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Re: Fire in the hole!! (5/12)
 7/30/15 12:36pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

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How long ago did you put the new engine in it? It's possible the valves are not adjusted correctly. That could cause both a spitfire out of the intake, and exhaust backfire if the valves are too tight. An exhaust leak will also cause exhaust backfires.
Ignition timing, plug wire cross-fires, lean fuel, vacuum leaks.....any or all of these can create the issues you have. Just gotta eliminate one at a time until you find the problem. Thumbs Up

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Re: Fire in the hole!! (6/12)
 7/31/15 10:07am
kbrin
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coral springs, FL - USA

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This engine has 200 or so miles. Just replaced the holly 600 with a new one and the stumble is gone. but still concerned!! Can i check the valves without pulling it apart ??

Thanks


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Re: Fire in the hole!! (7/12)
 7/31/15 10:08am
kbrin
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Im now thinking of going EFI???? any comments on this?

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Re: Fire in the hole!! (8/12)
 7/31/15 12:34pm
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Checking/adjusting the valves will require removing the valve covers...and whatever might be in the way of doing that(smog equipment, etc).
Has it belched fire since the carb change? New carb may have fixed all of your issues....
Some folks here have gone the EFI route....hopefully they will chime in on that, or you could start another thread asking for info about it. Thumbs Up


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Re: Fire in the hole!! (9/12)
 8/6/15 11:51pm
kbrin
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coral springs, FL - USA

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new carb and no light ups anymore. BUT it still stumbles when its warmed up. on the road it is ok but around town it will "load up with fuel" at stop lights and take a few seconds to run it clear, then its ok until the next time i idle for a bit such as a light? I am thinking ignition. the engine setup is all new BUT I have the original distributor with new points,cap rotor etc. I haven't looked into valves yet (just lazy!)

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Re: Fire in the hole!! (10/12)
 8/7/15 11:43am
lukesvetteLifetime Member
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If your idle adjustment is good, sounds like a blown power valve to me... Simple to fix...
Re: Fire in the hole!! (11/12)
 8/7/15 2:00pm
kbrin
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coral springs, FL - USA

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81 beauty all original (not anymore!!) Its more fun now!


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Thanks for the info. Call me stupid but what exactly do you mean by power valve.
Id like to check this out and maybe fix and kill this gremlin!


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Re: Fire in the hole!! (12/12)
 8/13/15 7:36pm
kbrin
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coral springs, FL - USA

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81 beauty all original (not anymore!!) Its more fun now!


Joined: 3/25/2014
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Ok Guys.. I have a new carb (not rebuilt) installed to see if I could eliminate the stumble and loading up at idle. 
81 350, Starts perfect, runs at speed perfect but around town its still stumbling when taking off from a light or idle condition for more than 30 secs. temp stays at 200 +/_ in south florida where the outside temps are averaging 92 so I am pleased with this. I have a TKO 5 speed so in first no problem second she will load up and I have to back off to burn off the stumble? then ok until the next light. Timing OK, does not idle or run rough so I am looking for other reasons She seems to not burn everything at idle. I was going to EFI her but I am thinking its just going to do the same thing. Im thinking ignition, maybe hotter plugs? any Ideas would be great..
Thanks


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