Gregofracine
New member
1993 MCM 4.3LX with 600hrs. Accelerates well to WOT (4000 RPM), but only for 30 seconds. Engine rapidly decelerates, "pop-pop-popping" as it comes down off plane (overly lean?). Retarding throttle will catch idle RPMs. Engine will accelerate again, and decelerate again. Timing has been checked, ignition components have been changed, spark plugs have been replaced, a different fuel tank and line has been used, bypassing the fuel/water seperator, carburetor has been replaced, all with no improvement. Compression check reveals middle 2 cylinders at 80psi, remaining cylinders at 125 psi.
Engine has been removed. Heads show nothing extraordinary. Spark plugs look normal. Head gaskets appear intact. 2 Cylinders "show some rust near top with minor roughness". Exhaust risers have 1/2 of each water baffle missing. Past engine history includes 2 sparkplugs with electrodes melted away--gone. Timing was suspect as engine resisted starting rotation and might run on or diesel at shutdown. Timing issue has been corrected (I believe). Mechanic wants to install a Long Block, replace ignition components (again) and tear down to inspect and rebuild carburetor (3 seasons new). Thoughts?
Engine has been removed. Heads show nothing extraordinary. Spark plugs look normal. Head gaskets appear intact. 2 Cylinders "show some rust near top with minor roughness". Exhaust risers have 1/2 of each water baffle missing. Past engine history includes 2 sparkplugs with electrodes melted away--gone. Timing was suspect as engine resisted starting rotation and might run on or diesel at shutdown. Timing issue has been corrected (I believe). Mechanic wants to install a Long Block, replace ignition components (again) and tear down to inspect and rebuild carburetor (3 seasons new). Thoughts?