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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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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22714
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
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?
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?
Joel Adams
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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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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22714
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
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.
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.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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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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Im now thinking of going EFI???? any comments on this?
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22714
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
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.
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.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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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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If your idle adjustment is good, sounds like a blown power valve to me... Simple to fix...
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in Forum: C3 Engines, Driveline and Handling
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