Backfired .....
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Twin 454 mags ..one with 10 hours one with 30 or so .... at WOT or close one motor will backfire ... so far only twice ..and just once per occurnace .... I am guessing carb but dont really know which motor .. Everthing seems ok oil pressure temps ect .Suggestions on where to start ? Thanks ..
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Originally Posted by offthefront
Twin 454 mags ..one with 10 hours one with 30 or so .... at WOT or close one motor will backfire ... so far only twice ..and just once per occurnace .... I am guessing carb but dont really know which motor .. Everthing seems ok oil pressure temps ect .Suggestions on where to start ? Thanks ..
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I would say that you have a valve hanging up or going bad.
At WOT I dought the carb could be the cause.
If it was a lean condition it could cause the valves to get TOO hot and that could cause a backfire.
At WOT I dought the carb could be the cause.
If it was a lean condition it could cause the valves to get TOO hot and that could cause a backfire.
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Originally Posted by cuda
What type of carb do you have?
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Is it popping back through the carb or out the exhaust? A lean mixture will cause the carb to pop at sustained high RPM as the engine starves for fuel.
Usually if a cap or rotor is bad the idle will not be good, but not always. Are both engines pulling the same RPM?
How much time is on the valve springs?
Usually if a cap or rotor is bad the idle will not be good, but not always. Are both engines pulling the same RPM?
How much time is on the valve springs?
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Originally Posted by Edward R. Cozzi
Is it popping back through the carb or out the exhaust? A lean mixture will cause the carb to pop at sustained high RPM as the engine starves for fuel.
Usually if a cap or rotor is bad the idle will not be good, but not always. Are both engines pulling the same RPM?
How much time is on the valve springs?
Usually if a cap or rotor is bad the idle will not be good, but not always. Are both engines pulling the same RPM?
How much time is on the valve springs?
Last edited by offthefront; 01-01-2005 at 09:36 PM.
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After a good run I would pull a few spark plugs and see if they read lean. Are these Gen V engines with the mechanical fuel pump mounted on the raw water pump?
You may want to hook-up temporary fuel pressure gauges to each engine and see if one side has a bad or clogged fuel pick-up in the tank. Did you have the carbs gone through?
I wish you were here in SE Florida where I could help you HANDS ON!
You may want to hook-up temporary fuel pressure gauges to each engine and see if one side has a bad or clogged fuel pick-up in the tank. Did you have the carbs gone through?
I wish you were here in SE Florida where I could help you HANDS ON!
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If you can not verify that the motor is leaning out try the ignition system. Had the same problem. It was the coil. Watch the tachs while you are coming up to WOT rpm. You will see the tach bobble on the motor that pops. Change the coil on that motor (hell or both motors, coils are cheap). Also change/check plug wires, plugs, distributor cap and rotor.