Occasionally you will get a phone call from a shop stating that the engine you just sold is “locked up.” Although this can be caused from numerous possible issues, let’s discuss spacer plates.
spacers on both sides of the flexplate
The missing spacers can also allow the flywheel to hit the back of the block locking up the motor, or the torque converter bolts to hit the block when rotating causing a lock up or knocking noise. Some of the engines with spacers also can have a no start situation due to missing or in the wrong place spacers due to the crank signal tone wheel being part of the flexplate.
This is also a good time to bring up the use of a thread sealer on engines with drilled through cranks. It is always good to use a thread sealer (required on many) on the flywheel bolts to prevent oil leaks through the threads. This is a simple mistake that happens more times than you might think.
Christian – Lead Technician / Tech Support
Some engines are designed to use spacers on the back of the crank before the flywheel, after the flywheel, and some on both sides. The cranks on these motors are also often drilled all the way through the crank instead of being a blind hole.
When the flywheel is swapped over or rear main seals are replaced, which should be done on all engine installs and required on most warranties, these spacers are sometimes left off allowing the flywheel bolts to go all the way through the crank hitting the block or main cap on the inside. This will cause the engine to lock up.
