engine wont idle

[PromiseKeeper]

I finally got the 305 that I picked up in my truck. It is an 83 and had the early fuel injection system. It didn't have an intake on it, so I put my old one on it and installed a fuel pump. It has a 2bbl Rochester on it. The Rochester worked great on my old engine, but since the swap, I cant get it to idle. Runs great on the road, no hesitation, good acceleration. Pull up to a stop sign and it dies. I've replaced all the vacuum lines and put a new mounting gasket under it. Seems to run the best at about 4 turns out on the adjustment screws which seems like a bit much and have the idle set high to try and keep it running. Any suggestions on what to try? Also, I did set the timing with a light at the specs on the sticker under the hood. Thanks guys!
Scott

[rich weyand]

I am assuming you disconnected the vacuum advance when setting the timing.

The proper idle adjustment should be about 1-1/2 turns out from stop.  Sounds like a blocked fuel passage or orifice in the idle circuit.  Blocked orifice is probably more common.  You could back the idle screws all the way out and see if you can blow out the orifices with some air.

[PromiseKeeper]

Rich, yes I had the vacuum advance disconnected and the line plugged. I'll try blowing out the orifices and try again. It just seems strange that this carb worked great and suddenly doesn't? I guess you can dislodge lots of stuff when you take things apart! For the record, I replaced the fuel filter as well. Thanks!

[Fairlane514]

Rochester carburetors usually have a 3 turn out starting point of the idle mixture screws.  What degree did you set your initial timing?   How do your brakes feel? There is a check valve in the booster that can create a vacuum leak when bad.

[Powerdriver1958]

Everything I've read so far points to a vacuum leak of some sort .

[Fairlane514]

if you turn the screws all the way in while its running does it kill the motor?   If you put your hand over the choke horn does the idle pick up? 

It does sounds more a vacuum leak. Its possible the leak is around the intake gaskets, since you said you just installed it. 

[rich weyand]

Yeah, a serious vacuum leak will make it lean as heck, and above a 16:1 air/fuel ratio, the fire will go out.

[PromiseKeeper]

Not saying it is impossible, but the intake was just installed before the motor went in. There seems to be good suction when putting a rag on the choke horn. Brakes feel OK, I think the timing was set at 12, compensating a bit for the high idle that was needed to keep it running. Would you guys still try taking the screws out and blowing it out? I ha vent had time to do anything yet.

[Fairlane514]

Try turning the screws all the way in while its running and see if it kills the motor.  Use a vacuum gauge on a full manifold vacuum source and see what kind of reading you get and how the needle reacts.

 When you place your hand over the choke horn does the idle speed up?  If so, you have a vacuum leak. 

If you have another carburetor, you can try that.

Try removing all sources of vacuum from the carburetor and plug all ports and see if it runs better. Then start reinstalling your vacuum lines one at a time until the problem returns, then you may have found your leak. This includes the PCV and power brakes.

[PromiseKeeper]

I took the adjustment screws out of the carb, shot carb cleaner into the orifices, cleaned up the screws, and blew about 30 lbs of air pressure into the orifices. There was a noticeable improvement, but still not the way it should be. I think I'm on the right track, just need to fine some time to play with it. Everything I've done has been a step in the right direction. Looks like its a combination of several things! Keep the suggestions coming! Thanks!

[Fairlane514]

There are several suggestions you haven't tried, so let us know when you have done all of those.

[PromiseKeeper]

yes, right now life is busy so its on the back burner. Thanks