: 472 Onion

05-16-04, 09:44 PM
Hi all,

Need a little bit of help. Its been a while since I've been on an old school car. Got this 71 caddie that had a replacement 1973?? 472 put in it. Supposedly the new motor was locked up when it came to me. I put the plugs back in and got it to run, but not well. THe wires, cap, rotor, pickup tubes in the carb, and the resistor wire(newer motor had HEI so i removed the resistior wire) were all repaired by me. THe car runs and idles better, but will dog down at speed, and eventually not be able to move. It will also backfire badly with high throttle.

I suspected a fuel pump, but volume seems to be good. Client supplied a new pump, but for wrong year. In the meantime, I dropped the tank since the filter had already clogged up with crap. Strainer was ripped open, but otherwise spotless. I'm going to recommend a new pump, strainer and filter and choke pull off to keep the secondaries from flopping open.

Engine idles and runs relatively well otherwise. Did I miss anything? One thing I noticed is the mixture adjustments don't seem to make much difference. Maybe with more fuel it will. My only other thought is to get a rebuilt carb since sometimes kits won't fix the problems. Since this isn't the original carb for the car (came with the junkyard motor) I'm not sure how far to trust it. Thanks for reading a long post.


05-18-04, 04:05 AM
Check your distributors vac advance it might be your problem.

05-19-04, 02:47 PM
Try a new set of spark plugs. I have seen all of the symptoms you have described caused from bad plugs. The plugs may look perfect but may not fire reliably. The 472 needs frequent plug replacement (every 6000 miles or less).