Hi. I have a 455 Centurion 73. I recently exchanged the old rochester carb with a new Edelbrock 750 carb. I changed it because the rochester was starting to have difficulties starting, using to much gas and running very bad while the engine was cold. With the new one with electrical choke it started like a dream but the same problem has been slowly re appearing. When its cold it runs like a dream. cant hear anything but when its hot it starts running un even. That started only when it was on idle, now its doing it on higher rpm as well. first only a little while drivig slow and now it does it when having medium rpm at the highway. The Sparkplugs is Adelco and new last year. The cables is also new. I have no idea what this could be but im guessing the ignitor or fuel pump have been getting bad? The distributor cap and rotor is also new last year. Any advice here? If it simply turning some screws i most likely will be earning some money tonight so a quick response would be sweet. Most of all, i just want the car to run nice because it deserves it Thanks
I hope that you did not discard the Rochester carburetor. The Edelbrock is OK but the Rochester is what is right and will perform best for your engine. That being said, it sounds like you may have a problem that is not related to the carburetor. We will need more information to help you straighten your car out.
Well, first, what is your name???? then,,, we really need more info..... when you say that it runs uneven,,, do you mean like a dead miss.. or a surge,,, there is a difference.... that said,,,, a hole in the vacume cannister diaphragm can cause a surge at speed , with a even throttle.... and so can a lean condition.... and so can fuel supply problems.... when was the last time the fuel filter was changed....?? a hole in the rubber parts of a fuel line on the suction side can suck air into the line causing disruption.... a engine that is running hot or cold can run erratically.... To start out,, go back to the basics,,,and get each thing right so you know each item is good.... check and set the ign timing... then check out the fuel pressure/supply/ filter,,,,it aint the carb because you changed it out and the car is still doing the same thing... does a 73 have the little vacume doors in the snorkel of the air cleaner,,,and does it have the thermal vacume /heat switches there????? all the mechanics back then cussed that stuff because they caused problems that made the car run goofy if something got wrong with one of them...... systematically go thru each item that can cause a problem , eliminate them one at a time and get back with us so we can help....
Yep, what they said. sounds like it is likely not carb related. More of a vacuum issue somewhere. And, if you want to sell that quadrajet core, I'll take it.
I just rebuilt my carb and am noticing similar issues. Since your carb is new, you can rule that out. Unless there is a bad seal somewhere with your carb. or you forgot to put an o-ring back on like i did!!! :ball:
Hi. My name is Kristian. Thanks for the replies, I will start summoning up what we have done and hopefully that will help you experienced guys to find a solution to my problem because i would really like to go out in my beautiful centurion and cruise. As it is now, i dont dare to in case the car will stop. http://img845.imageshack.us/img845/8047/blablas.jpg This picture shows the engine before the carb was changed. The distributor was connected to a vacuum "tower" and the vacuum cannister on the torpedo wall was hooked to the carb. http://img59.imageshack.us/img59/9350/20120707163602.jpg This picture is after the new carb is installed. According to the innstallation video from edelbrock we changed the vacuum hose from the vacuum "tower" to the carb itself. We also routed new vacuum hose from the vacuum cannister to the vacum "tower" Since there was no vacuum connection on the rear on the edelbrock as the rochester. We also changed to a new fuel filter from edelbrock. After doing this modification the car started at first try and the new electric choke was acting like it was supposed to. After a while and the engine was warm the idle was fine and the test drive showed that the car was running smoothly at all engine rpm's. A great improvement compared to the old carb. The only problem experienced was the lack of control of the heater system. The ac compressor did start and stop accordingly, but not possible to change the air flow and different modes. The vacuum hose at the vacuum cannister was removed and checked for vacuum. No vacuum found. The vacuum hose was removed from the vacuum "tower" and was connected to the carb. This restored the heater controls to normal function. The car started easily both cold and warm. My problems started after a few days and grew for every trip with the car. When starting the car cold it starts normally and runs fine. In the beginning of this problem it was only at idle that the car was running uneven/misfireing. http://www.youtube.com/watch?v=hVxoxcrUbxA&feature=youtu.be Video and sound of idle behaviour. After the problem started is hard to start when warm. Must use lot of throttle and turning the engine over for several seconds. Further on the problem is showing up at higher and higher rpm's. We have tried to look for vacuum leaks by using start gas around the carb and all the vacuum connections when running. We have added hose clamps where possible to ensure no leaks. The last ride i took with it it started getting real bad. I was having problems getting home and had to have as high rpm as possible to not make it misfire. And when at idle it stopped. we have also been adiviced to check the compression for possible valves not closing properly. Before this problem occurred we could not feel any blow through from the crank case hose going to the air filter. A local mechanic has informed us that this kind of behaviour could be the result of valves not closing properly. I hope this explains my problem better @DeeVeeEight The rochester is stored on the shelf. I wanted to changeto the edelbrock of two reasons. Didnt have the skill or time to rebuild the rochester and im going for the Edelbrock performance kit this fall. The rochester will be kept on the shelf as long as i have the car.
Sounds like the basic idle speed is too low.... raise it up to factory spec.... on a factory air car that would be about 650-700 rpm with a fully warmed up engine....also sounds like the ign . timing may be retarded.... if the vac advance is not hooked up right , the timing will be retarded....I think you may have the vac hoses routed wrong.... get a diagram of the vac hoses and follow it.... I dont think you have any major problems... it will be something simple that you changed someway....
What he said. Make sure your vacuum advance is connected to manifold vacuum, not ported. Not all vacuum ports on the carburetor are vacuum. If in doubt, run the vacuum advance hose directly to the manifold and see if that changes your engine activity.
