OMC cobra new long block back firing when first starting

[Rob2024]

Just replaced my long black with a rebuilt one. I have checked the timing, the carburetor all good. What would cause this back firing. Took video but unable to attach

 

[Rob2024]

Just replaced my long black with a rebuilt one. I have checked the timing, the carburetor all good. What would cause this back firing. Took video but unable to attach

 

[alldodge]

Not knowing what long block I'll ask is the cam and crank timing correct?

 

[Rob2024]

Not knowing what long block I'll ask is the cam and crank timing correct?

 

[alldodge]

Thanks, 4.3 reman
I'll guess it's either crank and cam timing is off, or the valves are not adjusted correctly

Do a quick compression test

 

[Scott Danforth]

What did you set the timing to?

 

[rolmops]

When you say long block, did you get a block with a warranty and was it tested as michigan motorz does or is it a local shop?
I had the same problem. It turned out that I had set the timing on to the exhaust stroke instead of the compression stroke

 

[Bt Doctur]

incorrect firing order, the V6 is 1,6,5,4,3,2 clockwise

 

[Bondo]

Just replaced my long black with a rebuilt one. I have checked the timing, the carburetor all good. What would cause this back firing. Took video but unable to attach

Ayuh,..... Welcome Aboard,....... What killed the old motor,..??
Generally speaking, a lean condition would be my 1st guess, or the timing is off,...

 

[Lou C]

Or one of the intake valves is too tight and staying open allowing the flame front to travel back to the intake manifold