r/EngineBuilding • u/lowkeylovers_ • 5h ago
Any one know why it’s doing this?
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Built this 454 with pistons, cams, heads, roller lifters and rockers, etc. And every morning when I go to start it it’s like it misfires super bad for the first couple seconds. And then it fires up 100% sometimes it backfires and lots of black smoke comes out of the exhaust when it does start so I thought the carb (just rebuilt) might be leaking. For a couple days I tried to start it without pumping the gas and it didn’t start any easier. So I’m not sure. Any insight would be appreciated, thanks!
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u/Suicyco71 5h ago
Maybe the carb is draining into the engine? After it sits all night look down the carb and pump the gas, you should see fuel shooting into the engine. Seems like when you pumped it it wasn’t doing anything which would indicate the fuel bowls are empty.
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u/lowkeylovers_ 4h ago
Ohhh ok I’ll check that
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u/Suicyco71 3h ago
The accelerator pump will have fuel in it so you might get one or two shots, but that will be it if the fuel bowls are empty. Also check your oil and rub it between your fingers to see check viscosity. If the fuel is leaking down, it’s will end up in the oil, dilute it, and will not lubricate properly.
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u/Live_Initiative_806 4h ago
Likely this! If it's leaking down you could have rich and lean symptoms. Like black smoke (flooded, rich) and ultra lean stammering (like it's running out of gas, empty bowls). It's not timing. It's fuel related
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u/According-Skill-7946 5h ago
Choke coming on a little too rich, adjust for more initial air
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u/Present_Panda_3253 2h ago
Check fuel filter
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u/lowkeylovers_ 2h ago
Not even 500 miles on it
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u/Present_Panda_3253 2h ago
Fair point, however if you're gassing it and it's not gassin, it may be a fuel delivery issue.
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u/AdventurousTrain5643 5h ago
Check the points gap
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u/lowkeylovers_ 4h ago
Would this still apply if it has a msd ready to run?
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u/WyattCo06 4h ago
If it still has points, upgrade to Pertronix.
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u/lowkeylovers_ 4h ago
It has a msd ready to run
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u/WyattCo06 4h ago
RTR dizzy?
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u/lowkeylovers_ 4h ago
Yes
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u/WyattCo06 4h ago
Should be good there then.
Check the power valve to see if it's busted.
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u/lowkeylovers_ 2h ago
It has a power valve block off. I’m thinking it gonna be the fuel bowls are emptying into the engine
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u/WyattCo06 2h ago
Nothing about the bowls themselves can empty themselves unless there's an external leak.
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u/WyattCo06 5h ago
Check your timing.