Hi all, I have a '75 W200 with a 360 and a holley 2bbl carb. I bought a new carb for it a few months ago and I've been having trouble getting the mixture right (at least, I think that's my problem). It is used primarily as a plow truck, but it does see some highway use. It seems that however I just the mixture screws once the truck warms up it wants to stall out when taking off from a stop. If I'm easy on the throttle and take off slow it runs fine, and if I take off hard it does ok, but as soon as I try to take off like a normal person it wants to stall. I have to pump the gas to keep it running. Any ideas as to what my problem could be?

 

If the truck idles well, it is not anything in the adjusting screws. You should set the idle with a vacuum gauge and shoot for the highest vacuum with the correct idle rpm for your motor. this should be done after the engine has warmed up. Three things come to mind with the stalling problem; 1 accelerator pump problems 2 vacuum advance in distributor not working correctly 3 jetting to small. (maybe 4; power valve. mildly possibly but not likely)
Does it go down the road smoothly once you get going or do you feel a "surge" in the engine while cruising at a steady pace (not much load on engine)? Any surge while driving at a steady pace could indicate jets that are too small (lean).
You should see a solid stream of fuel coming from the accelerator pumps if you look down the throut of the carb when you are operating the throttle lever. Even if the engine is not running, it will do this (if the fuel bowl has fuel in it). So this is a good way to see if the accelerator pump is working. No stream means it is not working. A dribble or weak stream means it is not working up to par or just partially working.
For the vacuum advance, pull the line off the vacuum canister while the engine is idling at 1500 rpms, you should notice a change in rpms.
hope some of this will help, if not, we'll keep trying.

 

if it keeps stalling you could adjust the timing so that it should not stall as easily.

 

i had a similar truck and called summitt racing got a aluminun dual plane intake and 650 holly 4 barrel carb and changed out the troublesome 2 barrelactually it ran alot better after the switch and did not hurt mileagae , mine used to whistle , and it always had a cold stumble even after a rebuild kit

 

Thanks guys, still can't figure it out. I set the mixture screws with a vacuum gauge, so they should be fine. The accelerater pump is working fine, there is a nice stream of fuel when I step on the gas. I haven't actually unplugged the vacuum advance line, but I did look it over and sprayed some starting fluid on it and nothing changed, so I don't think the line has a leak in it.

Should I see anything physically move at the distributor when I open the trottle? Like any kind of rotation of the distributor?

I'm not sure what size jets are in there, I'm assuming they're the same as what was in the old carb, but I'd have to open it up to be sure, and that's a real pain! But I guess if it comes down to that...

Could it be an ignition problem (other than timing)? I had a spark plug wire fall on the exhaust manifold which melted the rubber coating on the wire and caused the wire to short directly to the block. I didn't replace the wire, I just ziptied it so the bare part wouldn't touch anything. Could the bare wire be an issue?

 

Replace the wires. Any moisture in the air will cause arcing and less than optimal performance without the insulation. If you are in there working on anything and brush against it you will wish you replaced them. LOL