I'm working on my 88 W350 w/360 and 727 automatic. My first question is about the basic settings for the idle mixture adjustment screws on the Rochester 4 bbl carb. This carb was rebuilt by PO, and has the idle screw plugs removed so the screws are visible. I read in my Mopar service manual for this truck that I should do some hocus-pocus with propane to set the idle screw adjustment. My thinking is that is just plain nuts! Neither the Mopar manual nor the instructions that came with the carb rebuild kit give any "basic setting" info the idle mix screws. I am familiar with the old method of setting them for max vacuum with the RPMs set to a very low idle (but that might have been 40+ years ago??).
Can anyone give me the basic info needed to set the idle screws? P.S. This truck will never have to get smog tested, so anything close will probably be good enough. As it sets right now, she will start and run but has a very rough idle. I did find some major vacuum leaks the PO did not discover. So he might have adjusted the idle rich to make up for the vacuum leaks. The engine seemed to idle smoother (but not good) before I solved the obvious leaks.
The engine balance might just be related to the idle screw settings, but it definitely has a harsh vibration, very noticable at idle, and less so at driving RPMs, but it still seems to have some vibration that my older 86 360 does not have. I suppose anything is possible, like maybe the converter threw a balance weight. But are there any engine balance issues to be aware of? I did a compression check and found all 8 to be within 5 psi, from 135 to 140. This engine supposedly has less than 50K miles on it, so I doubt it is a cylinder problem. All new plugs, wires, and cap and rotor, and I have pulled all plugs, set them on the exhaust manifold and watched for a good strong spark at every plug while cranking it over. So I doubt I have an ignition miss.
Your thoughts and replies are appreciated!
Thanks,
Paul in MN
Can anyone give me the basic info needed to set the idle screws? P.S. This truck will never have to get smog tested, so anything close will probably be good enough. As it sets right now, she will start and run but has a very rough idle. I did find some major vacuum leaks the PO did not discover. So he might have adjusted the idle rich to make up for the vacuum leaks. The engine seemed to idle smoother (but not good) before I solved the obvious leaks.
The engine balance might just be related to the idle screw settings, but it definitely has a harsh vibration, very noticable at idle, and less so at driving RPMs, but it still seems to have some vibration that my older 86 360 does not have. I suppose anything is possible, like maybe the converter threw a balance weight. But are there any engine balance issues to be aware of? I did a compression check and found all 8 to be within 5 psi, from 135 to 140. This engine supposedly has less than 50K miles on it, so I doubt it is a cylinder problem. All new plugs, wires, and cap and rotor, and I have pulled all plugs, set them on the exhaust manifold and watched for a good strong spark at every plug while cranking it over. So I doubt I have an ignition miss.
Your thoughts and replies are appreciated!
Thanks,
Paul in MN
Comment