Carb acting up and need advice please

[351windsorbronco]

Ok i have a built 351w as described in my signature. It has a Holley 670cfm street avenger carb on top, with good aircleaner. My problem is that it is backfiring every once in a while, and i know it doesn't have to do with the timing. My father has been saying it is the power valve, but i don't think he really knows what hes talking about. do you think it needs to be rebuilt? its not that old *added last year to my list of mods.* Do you think its got some dirt in it or something? give me some advice please.

 

[Justshootme84]

Usually, backfiring is caused by improper timing or flooding. Try adjusting the float level or replace the jets. I think the Avenger series has a Power valve protection unlike the older carbs. You can also get advice directly from Holley thru their website. JSM84

 

[351windsorbronco]

i am almost totally sure its not my timing because i have had it at anywher from 8-16 degrees and it still backfires, i think its in the carb somewhere, but im gonna take a look at it and see what i can do!

 

[wrachet]

That absolutely has to be the cleanest engine I have ever seen.

Are you backfiring on acceleration?

Good luck. /emoticons/[email protected] 2x" width="20" height="20" />

Colleen

 

[351windsorbronco]

That absolutely has to be the cleanest engine I have ever seen.
Are you backfiring on acceleration?

Good luck.  /emoticons/[email protected] 2x" width="20" height="20" />

Colleen

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thanks, yeah, its just when i accelerate a little hard. but it doesn't always happen

 

[wrachet]

thanks, yeah, its just when i accelerate a little hard. but it doesn't always happen

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Okay, another question for you...

When you accelerate hard and it backfires, are you starting from being stopped and idling such as at a stoplight?

Colleen

 

[351windsorbronco]

Okay, another question for you...
When you accelerate hard and it backfires, are you starting from being stopped and idling such as at a stoplight? 

Colleen

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yeah that is correct

 

[BroncoBubba]

yeah that is correct

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Check your accelerator pump for adjustment...Backfires are also caused from not enough fuel especially off idle (Lean Backfire).

Also, since it has been backfiring you might have damaged the power valve (I am not sure if the new street avengers have them so check that out first), which will make it run very inconsistent especially off idle.

Good Luck... /emoticons/[email protected] 2x" width="20" height="20" />

 

[92 3/4 ton bronco]

Do know know the diffenece between backfire and muffler explosion? Not to be sarcasict or anything just a question. Is it coming from carb or exhaust? If it is coming from carb then its backfire usualy caused by the fuel in the intake being ignited. This comes from lots of causes. I would check the ignition system first, that is plugs, wires, ect. Also the acclerator pump can cause this but usualy only when cold as the engine needs more fuel. When it is hot most of the time it will not. But as far as power valve, if you have the usuall ford 2 bbl. then the power valve will be blown because the backfire destroys them usualy.

 

[351windsorbronco]

im sure its in the carb, its a holey 4bbl, the street avengers supposedly have a protector that keeps the power valve from going bad., so that eliminates that. P.S. do these things have fuel filters in the frame hidden somewhere. i looked but didn't find one, do you think that that could be it (dirty fuel or something getting in the carb.