454 backfire

[BADSS70]

Recently, my 454 has developed a backfire under a heavy load. Specifically, when I jump on the engine just as the car is shifting to second the engine is backfiring. Thought someone might know what I can try to solve the problem.

[BowtieThunder]

Could be a timing Issue or even a coil going bad

[BADSS70]

The engine is all original and has points. I was thinking of changing it over to HEI. Do you think it would help?

[BowtieThunder]

HEI would be better for sure...

[cny first gen 71]

Just a single backfire or a rappid backfire like poping back through the carb many times when accelrating?

[BADSS70]

Just a single backfire. The car accelerates fine up until it is about to shift and as is going into second I get the backfire.

[cny first gen 71]

Mine did something simmiler to that but was breaking up a bit to but not all the time I found a plug fouled, replaced that and all was good. I would try to narrow down the problem before switching over to electronic ignition. But the switch over is worth it eather hei or pertronix. I went with pertronix and havent looked back

[TrunkMatt]

Is it a backfire in the Carb or Backfire in the Exhaust (aka Afterfire)?

 

There are very different causes to each...

 

Carb Backfire usually = you could be going too lean, or your timing too advanced.

 

Exhaust backfire = too rich (fuel burning in exhaust), timing not advanced enough.

 

There are other reasons... those are just the most common. Your timing could have slipped just enough (distributers do move with time... they have to have the retainer tightened once in a while)

 

Also, pull the plugs... make sure they look the right color. If you have one getting fouled, it could also cause backfire under load when your timing is all the way advanced.... as it is misfiring, building up mixture --- and then backfiring.

 

 

[BADSS70]

The backfire is in the carb, I will check the timing and plugs to see if fouled. After that I will check the carb setting.

 

Thanks for all the advice I will post again when I find the problem.

[stangeba]

Plug wires may need to be checked also and the cap.

[Mike 57]

I think I would start with a tune up. As points wear the timing retards. If you have access to a dwell meter that is the best way to adjust the points. Lots of carb issues are ignition related.

[BADSS70]

Procrastinated a little because of the winter but it was nice this weekend so I took a good look at the engine to find the problem. I took it for a ride and the problem got worse. I noticed that it would run fine but when I was going up hill or pushing the engine it would backfire and loose power. Because the problem would get worse when under stress I figure it was fuel problem and not an ignition problem. Well I was right I check the fuel lines and the rubber was cracked. There were no immediate leaks but when I moved the rubber around I saw some drips of fuel. After replacing the lines the problem was gone.

 

Thanks for all the suggestions and all the help!!!

[Machtuck]

I had a similar problem a few years ago. I was completely stymied as i had changed everything in the ignition. I hooked up a fuel pressure gauge and fuel press went to zero at WOT. Changed fuel pump and no joy. After inspecting everything from tank to eng, i found that fuel hose from chassis to pump was collapsing when i revved the eng. it was a new line but had no backbone. I then used a piece of trans cooler line...problem soved.