I have a 1972 454 all original. The car runs great, smooth idle, good power, and cranks with just a touch of the key, but with one exception. When I accelerate hard to get the rear jets to come in, the car just floods out and I can see some black smoke coming out of the tail pipe. If I continue to hold the accelerator down, it will finally catch up and the car comes on with full power. If I slowly accelerate up to full throttle everything seems to go Ok. This is particularly annoying when I am going to pass a car. The carb was rebuilt before I got the car, so I am assuming that there was a problem with the rebuild from the beginning. Does anyone have any ideas what the cause might be. I was even told by one mechanic that it might be a bad coil. I haven't changed it out to see if that is it, but it seems a little far fetched to be a coil problem. Thanks, Jimmie

Ignition breaking down under load doesn't sound so far-fetched, but it still sounds like a carburetor problem. If the carb was rebuilt, it may have simply had a zip kit put in rather than truly rebuilt, or whomever rebuilt it wasn't that good at it. Quadrajets are excellent carburetors, but it takes someone who knows what he's doing to rebuild one and set it up properly.

Has the engine been modified from stock? That could change the jetting appropriate for the car. It could be the float level not set properly or the accelerator pump. I would suggest finding a good carburetor shop who has someone who knows what to do with a Q-jet.

check the choke pull-off . it slows the opening of the rear meatering rods leting too much fuel !

Yes, check the pull off first. Then check the secondary air horn flap spring tension. This looks like the rear choke plate. On the right side (pass) of the carb is a tension screw the proloads the air flap tension. There is a small set screw with an allen head pointing down to hold the adjsutment screw in place. It likely has too little tension and allows the air flap at the wrong speed. Too fast or too slow will cause severe problems. This is a very overlooked adjustment when these carbs are rebuilt, but very important.

Ken Styer

Well it certainly sonds like carburetion and once again Im gonna echo what gunslinger said about it. Any mods? And what was the disposition of that rebuild? a few gaskets and some gumout? metering jets? who did it? I also tend to think a bad coil would cause a bog or break up when not under a load, i.e. if it revs right up in neutral with no problem its alot more likely to be fuel that an ignition issue.Good luck and let us all know when you get it right.

|UPDATED|12/23/2003 3:33:22 PM (AZT)|/UPDATED|

Thanks, all for the replys. I think I am going to just take it to a good reputable mechanic and let him rebuild it. I would try, but a carb has a lot of small parts that have to be calibrated just right to make it work properly. Jimmie