80 cheiftan 440-3 stalls out when put into gear(vaccuum drops)

[mahend]

i have to have my idle set all the way in to keep motor running and get 15 on vaccuum gauge, than when i step on brakes and put into gear vaccuum drops to nothing and dies any ideas? have replaced vaccuum lines,but not sure wich ones should go where looks like the motor has had some tinkering with.

[DaveVA78Chieftain]

Your problem could be carburator, vacuum, egr, ignition, or timing related.
For 78-82, if you have a M300 chassis, this could be a brake booster vacuum leak.  M400 and later do not have a vacuum brake booster. 
If you are not sure the vacuum lines are correctly installed, then you need the service manual.  There are good picture diagrams in Group 25 of the service manual.  If you do not have a manual, one is available in the store.  The chassis service and parts manual will save you tons of pain and frustration.

Dave

[GWINGER]

Spray carb cleaner near the base of carb and varoius areas of the intake manifold. Listen for a change in RPM's. The change in RPM indicates a leak in that area.
J

[RV Mech Tech]

mahend - for the engine to shut down with the idle all the way up you definitely have a major vacum leak - look for both the leaks Dave has suggested and definitely check for intake manifold leaks as Gwinger suggested - it sounds like your intake manifold gasket around one of the port(s) between the intake and the heads has burned out and anything you spray in that area will get pulled in to the intake port- if the gasket has burned or cracked at the bottom of the port you will hear a large hissing sound on that side in that area - (on Chev motors this covers the lifter valley and oil will get sucked into the intake port(s) - also check the base gasket for the carb -if it has burned near a large vacum port (large vacum port going to the vacum booster as Dave has suggested or the booster itself) - when you put your Winnie into gear the engine is under a load even at idle and the engine then receives more air than fuel because of the vacum leak and then stalls - RV engines are subjected to higher operating temperatures that tends to shorten the service life of some things such as gaskets and seals    Hm?

[mahend]

 thank you all i found base gasket leaking, and adjusted the mixture screws on the holley and was able to get idle down to a nice 750 rpms than found split in plug on 1 of charcoal cannisters and fixed ,i can now place in gear and not kill motor. this rv still needs lots of work but i am making progress. thanks again