Timing problems

[tommy8604]

1994 Crownline bought boat with locked up 5.0. I installed a 5.7 and have yet to get it to run correctly. Had issues before so I replaced fuel filter, blew out all fuel lines and vent, plug wires, new NKG plugs, distributor cap and rotor. Now the issue I'm having is its backfiring through carb. I've adjusted timing over and over and no stop to the backfiring. So I'm thinking it's the ignition module. Guess my question is could or would this 5.7 need a diffrent timing curve than the 5.0 that was in it? It is a thunderbolt IV mounted to cap. The number on it is 3F24A V8-22

 

[achris]

Is the back firing only at idle or at all speeds? Could you have the firing order wrong? If its not ignition, then it's a lean condition in the fuel system or an air leak in the intake. ...

Chris. .....

 

[tommy8604]

Idles really good now. Starts backfiring around 2500+. Carb was rebuilt last year and motor probably has about an hour on it.

 

[achris]

Check the firing order anyway (cheap, easy, quick, can't hurt). I'd also look at rocker adjustment. If they are both ok, check timing is advancing correctly, then look into the carb.

 

[tommy8604]

Ok thanks, at lake now and forgot timing light at home. Will go through it when I get back.

 

[bruceb58]

You are going to need and advance type timing light or timing tape to see if the advance is correct.

 

[tommy8604]

Checked valves and had a loose one, adjusted it. Cleaned sensor in distributor and rechecked plug wires, plug wires all good. Messed with timing (by ear for now) and now runs like a top. Thanks

 

[bruceb58]

Messed with timing (by ear for now) and now runs like a top. Thanks

Never set timing by ear. Please tell me you haven't run it that way on the water!