I have a 71 455 with 44,000 original miles.. runs great when cold.. warms up backfires and blows mufflers off... rebuilt distributor, new plugs wires, gas tank, gas lines, rebuilt carb.. Some are saying bad cam or sticky valve? Help...
this car sits for very long times and I would like to enjoy it... thank you Todd

 

Backfiring out the exhaust typically means the engine is too rich (excess fuel in the exhaust ignites when it hits the mufflers). This is likely caused by a choke that isn't opening when the engine warms up.

 

New carb no choke..

 

Hard to provide useful information with such a cryptic response. Is it a "rebuilt carb" (per your first post) or a "new carb"? What does "no choke" mean - is it not hooked up or is the choke plate removed completely? And what else is not hooked up or not stock? The mind reading thing isn't working yet.

 

Have the original carb. Had it rebuilt.... still did it put a new holly on with no choke on it..... still did it.. put a 3rd carb on new Edelbrock with a manual choke same thing...

 

Stock car 44000 miles on it never touched

 

Pictures and model numbers of the carb(s) might help.

 

Edl-1407 is the edelbrock number 750cfm
hly-0-3310s is the holly number 750cfm
the original is a Rochester quadrajet
It is the one I want to keep on it because it is original
I can take pictures when I get home I guess

 

Both the Holley and the Edelbrock carbs you listed are manual choke models. Unless someone has gone to the trouble to mechanically remove the chokes on both carbs, which would be crazy to do since a carb needs a choke to operate properly when starting and in cold weather, then what you are experiencing is exactly as Joe described in the first reply, that the engine is too rich since the choke is not opening.

Installing a manual choke cable is pretty easy, and I am sure that there are many threads here on how to do that.

Good luck.

 

It would appear that the carburetor has been touched several times.

 

Pictures will tell the full story.

 

Do this ! Good advice !

 

Both new carbs one with out choke......... butterfly’s gone from factory other open all the time... no pictures yet weekend got away from me...

 

Retarded ignition timing can cause this also.

 

Hey @The Tin Man any updates? Are you all good now?