Chevy 350 will not idle

[jack/ny]

I recently replaced the points in my chevy 350 which is in a 69 m715,
along with plugs,wires,cap roter coil with built in condenser. the motor will
idle fine while cold, but once warmed up it gradualy looses power untill
it stalls. The timing and points are dead on.

I've since had the carb rebuilt,and adjusted the valves with no change.
A friend of mine who has a shop came over to take a look. One thing he
did was spray starting fluid around the intake manifold and the idle did
pick up. He sugested maybe a new intake manifold gasket? One thing I'm
going to do today is replace the fuel filter, easier than pulling the manifold.

Any sugestions before I pull the manifold off.

Thanks
Jack

[brute4c]

First though is the coil...though you have a new one in there...

Have you checked the fuel tank vent line? If it is plugged or partially plugged, the the fuel will flow till there is too mch resistance in the line due to the vacuum in the tank...after it shuts down and relieves the vacuum it runs again fine...till the vacuum builds up again...

When it uits, take off the fuel cap and listen for the tank to inhale...if it does, then theres a vent issue...

[jack/ny]

After I did the first post I thought about putting the original coil back in.
I'll try that along with your sugestion about the fuel tank. I hope I still have
it?

Thanks
Jack

[jack/ny]

Well I replaced the fuel filters. I have one in the carb and one inline just
before the carb, the original coil was put back on also. Motor still idles
rough. I think it's air or fuel related. I cuped my hands over the carb and
the idle picked up and the motor sounded great, aslo sprayed a little starting fluid around the intake again with the same results, motor sounding good.

I had a thought about the intake, what if I took some gasket sealer like
Indian Head and just put it around the intake as a temporary fix. I don't have the time right now to pull the intake with the New Jersey MTA show
next weekend.

Ideas anyone.

Thanks
Jack

[randyscycle]

Sounds like you definitely have a vacuum leak somewhere up top.

Check very carefully around the carburetor base gasket and any vacuum hoses like the PCV hose or brake booster hose (if you have power brakes). Also check the PCV valve itself to be sure it is still intact. I've seen them fall apart and cause some rough running issues too. Pull it out of the valve cover while idling and put your thumb over the end. You should feel a click and then hear a slight change in the idle. If no change and the valve doesn't click, replace it.

If it does turn out to be the intake gasket, on a small block Chevy it isn't a big job to do at all and could be done in a couple hours with hand tools.