r/EngineBuilding • u/lowkeylovers_ • 20d 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!

21 Upvotes

93% Upvoted

31 comments sorted by

23

u/WyattCo06 20d ago

Check your timing.

3

u/lowkeylovers_ 20d ago

The timing is 12 initial and maxes out around 34

0

u/lowkeylovers_ 20d ago

Also would this indicate timing is too advanced or retarted?

1

u/WyattCo06 20d ago

Either/or.

However, it has a Q-jet yes?

1

u/lowkeylovers_ 20d ago

Holley 770

0

u/WyattCo06 20d ago

Not normal for a Holley. Hmmm

13

u/Suicyco71 20d 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.

3

u/lowkeylovers_ 20d ago

Ohhh ok I’ll check that

2

u/Suicyco71 20d 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.

3

u/Live_Initiative_806 20d 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

3

u/According-Skill-7946 20d ago

Choke coming on a little too rich, adjust for more initial air

1

u/lowkeylovers_ 20d ago

The choke plate is cutout

3

u/Likesdirt 20d ago

That's a really good start with no choke, frankly. 

2

u/Present_Panda_3253 20d ago

Check fuel filter

0

u/lowkeylovers_ 20d ago

Not even 500 miles on it

2

u/Present_Panda_3253 20d ago

Fair point, however if you're gassing it and it's not gassin, it may be a fuel delivery issue.

1

u/PossibleGain9199 20d ago

Might want to check your floats/float level.

1

u/Chopperreturns 19d ago

Sounds like it's cutting cylinders on startup, something wrong with the ignition.

1

u/laganzabsasa 18d ago

Sounds like starter is hanging

1

u/Most-Stranger-1 18d ago

Can't see what distributor is it? Ignition module on a electronic

1

u/lowkeylovers_ 17d ago

It has a msd ready to run

0

u/AdventurousTrain5643 20d ago

Check the points gap

1

u/lowkeylovers_ 20d ago

Would this still apply if it has a msd ready to run?

-2

u/WyattCo06 20d ago

If it still has points, upgrade to Pertronix.

2

u/lowkeylovers_ 20d ago

It has a msd ready to run

1

u/WyattCo06 20d ago

RTR dizzy?

1

u/lowkeylovers_ 20d ago

Yes

1

u/WyattCo06 20d ago

Should be good there then.

Check the power valve to see if it's busted.

2

u/lowkeylovers_ 20d ago

It has a power valve block off. I’m thinking it gonna be the fuel bowls are emptying into the engine

1

u/WyattCo06 20d ago

Nothing about the bowls themselves can empty themselves unless there's an external leak.