The Stovebolt Site Forums The Shop Area Engine Shop New 350 HELP

Just bought a '63 1/2 ton from a friend. He put in a new LM1 350 crate motor and I have two problems. It is set up with a '69 Z-28 intake and Holley 600. The engine only has 3K miles on it. I just got the timing set up correctly and put the vacum advance line to the correct port on carb. It runs 10 times better now. Here is the problems I still have. When running at cruising speeds 45 to 50 mph. the engine lunges and jerks irratically and intermittenly. When engine is pulling up a hill at this speed it runs smooth though. When I accellerate hard it runs fine as well. I changed the carb to a new Edelbrock 600 but exact same problem. The next problem that scares me is I noticed after running the engine and getting it hot I noticed exhaust smoke (blue) at idle and more from the right side than the left. What could cause this?

Any help appreciated,
Mike

Blue smoke generally means that it is burning oil, from what I know.

Drew

What's the total timing advance with the engine running at cruise speed, and the vacuum disconnected? It should be 37 degrees or less, increasing to about 45 degrees when you connect the vacuum. On a pull, the vacuum goes away, and you're left with centrifugal advance only. Just a few degrees of over-advance will cause the symptoms you're describing, trying to run the engine backwards at full advance. I do a distributor recurve on some applications, actually reducing the centrifugal advance and making up the difference with the initial advance. This gives better acceleration without getting too much timing at cruise speed. A too-lean carburetor in the midrange and/or cruise range can also cause surging at light throttle.

Check your PCV valve vacuum line to see if it's pulling oil through the line and burning it. If the inside of the vacuum line is wet with oil, it's the source of the smoke. Some aftermarket valve covers don't have enough baffle built into them to prevent oil from entering the vent system.
Jerry