My truck has always had a funny idle since I bought it this summer. I notice today that my fuel pump is leaking gas. I replaced the hose and now it looks like it is leaking out of the seam where it is put togather. Would this cause my truck to idle funny. I mean it runs fine but when I try to set the timing the timing light shows the idle going from 590 rpm to 700rpm just a idle up and down so I got to guess a middle area to set the timing. The mark wont stay still it jumps up and down. I figure this is the idle doing it since it wont idle at a steady rpm. or would it be the carburator. Either way I am going to replace the fuel pump today and hoping in a few weeks to be able to buy a new intake to put the edlebrock 4 barrel I got on to it. Also my new carburator I want to put on well I bought it this summer for another truck I had and now that it is gone I took the carburator back off and put it up in my shed do I have to worry about any seals going out in it? I know the come dry buy after i can gas though it I wonder if there is anything I might want to do to it before I put it on my truck I got now. It a eldelbrock 1411. I know a 750 is too big but when I bought it I was thinking bigger is better and thats was on my 390 so going onto a 351m Iknow its way big. BUt I am hoping to lean it out enough so that it would be okay.

 

It could also be leaking into the crankcase which will enrich the mixture thru the PCV valve etc and cause idle stability problems. If your dipstick smells like gas change the oil.

Just drop it in a bucket of gas and let the seals swell etc for an hour or so.

Being to big does not mean you need to "lean it out". A carb only delivers fuel according to the airflow thru it and load. Too big means that driveability and throttle response will be decreased. Fuel economy will be affected because of efforts to make it drivable.