SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: Santee_Native on July 24, 2012, 11:56:33 AM
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Had my rig out at El cap on Sunday all was working good but I had a slight backfire popping sound coming from my engine at wide open. Fuel pressure is at 6.5lbs and it's a new Holley 4150. Would that mean its too rich or lean? It was also lil sluggish out of the hole if I stood on it too hard it would stall. Would that mean the primary's are a lil rich?
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More accelerator pump? I don't know Holleys... Mine pops if I jump on it too quick, but if I flick throttle before I mash it to give it an extra squirt.
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Could be electrical/ignition
check for -
vacuum leaks
plug wires burnt/ worn
carbon tracking in dizzy cap
cracked electrode on spark plugs
worn cam lobe/lobes
burnt valve/ bent pushrod
there could be more
Daniel
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is it a backfire or a lean "pop"?
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Could be a lean pop it's only a wide open throttle. I'm thinking the primary's are rich and the secondary's are lean.
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Could be a lean pop it's only a wide open throttle. I'm thinking the primary's are rich and the secondary's are lean.
assuming your bowls are staying full, what are your jets set at? i was jetted too low and if i stood on it i would get a lean pop from the exhaust... almost like it was stuttering.
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If I stand on it dies out. If I just ease into it all is fine until the very top end thats when it has a pop.
Like when I'm coming off plane I watch for the wake as soon it's time to goose it I do and it stalls out.
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Did you ever get worked out? I have a chevy 350 doing the exact same thing.
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Sounds like weak valve springs. They are not closing fast enough. In a new Holley with the correct fuel pressure it should be close with the jetting and most likely it will not be that lean. A carburetor only passes so much air. I have had this problem an it was valve springs.
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have you looked at the spark plugs??? they should be able to tell you something!
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I would check your ignition system if thats a new holley. Timeing wires cap rotor etc. good luck. ;)
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check your timing, and advancement, if you're running a mallory unilight throw it away
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Sounds like weak valve springs. They are not closing fast enough. In a new Holley with the correct fuel pressure it should be close with the jetting and most likely it will not be that lean. A carburetor only passes so much air. I have had this problem an it was valve springs.
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Bingo! Problem solved!
Ray
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Well it is the off season guess its time for a new top end and get rid of my peanut port heads. Any recommendations on a complete set up?
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some 781 or 049 can be reasonable if in good condition, but if buying new, there is some good deals on aluminum heads too. then a single plane manifold (Eddy vic jr airgap, etc.) or tunnel ram, if $$ permits.
Might look into a cam upgrade too
Daniel
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Sounds like weak valve springs. They are not closing fast enough. In a new Holley with the correct fuel pressure it should be close with the jetting and most likely it will not be that lean. A carburetor only passes so much air. I have had this problem an it was valve springs.
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Thats my 1st thought...or a valve thats just set too tight...or both.