Hello wizards of the lost art and practitioners of Q-jet magic!
I've recently purchased and done a top-end job (bought with blown head gasket) on my first carbureted 4-wheeled vehicle (pretty familiar with sidedrafts on bikes though). It's an '84 C2500 with the M code 350. I ordered and installed a rebuilt M4ME from National, and have been having trouble getting the thing tuned.
I live in Flagstaff, AZ, where the altitude (depending on what part of the mountain you're on) ranges from 6800-7400 feet. This truck floods. BAD. At first it would idle for a few minutes, but if the truck was turned off and restarted, would flood and not restart. I appear to have fixed this by changing out the size 73 idle jets for 70s, but now it still floods on acceleration. I was able to drive around my neighborhood at sub 20mph speeds, but once I opened up the secondaries and got onto a larger road at about 45mph, it flooded at the stop light.
I've been working with National, and after many minutes of holding on their line, arguing with the service people, and being sent RICHER metering rods instead of LEANER, I've picked up a new hobby: pulling my hair out.
I currently have size 70 idle jets, primary rods are .052 M, and secondary rods are size DP with short/no power tip. Hanger is size L. The knuckleheads sent me secondary rods with long power tips, which, unless I'm mistaken, will cause earlier enriching of the secondary mixture (which I don't want). They are thinner around the base as well.
Anyone know a guide or have some info on tuning an M4ME for high elevation? The GM TSB I got from Alldata just suggests raising idle and advancing timing. The timing is good, but I can't take this out anywhere without flooding. I should mention this is a run-of-the-mill M4ME, no aneroid, no high altitude package.
Thanks for the help!
