r/LSSwapTheWorld

LQ4/4L60E crank spacer won’t sit flush—crank pilot/register sticks out too far. What am I dealing with?
I need some help from people familiar with LS crank spacing and 4L60E swaps because my current combination doesn’t make sense.
I have a 6.0L LQ4 that I’m mating to a 2003 4L60E with a Circle D 3200-stall converter.
Originally, I installed it using a factory-style dished 5.3/4L60E flexplate. That combination should have bolted together with the correct converter spacing. However, when I first assembled everything, it appeared that the torque-converter pilot was bottoming out in or against the crank before the converter pads reached the flexplate. This left a large gap between the converter mounting pads and flexplate.
Based on that, I mistakenly concluded that I had an early LQ4 with the longer crankshaft. I sent the Circle D converter back and had the converter pilot/face shortened so it could be used with a long-crank LQ4.
I later determined that my engine actually appears to have the standard short crank.
To compensate for the converter now being modified for a long crank, I purchased the approximately 0.400-inch crank spacer/adapter intended to be used with a flat 4L80E flexplate. My understanding was that the spacer and flat 4L80E flexplate would effectively give my short-crank engine the long-crank spacing that the modified converter now requires.
Here is the current problem:
The crank spacer will not sit flush against the crank’s flexplate-mounting flange. The raised center section surrounding the converter pilot bore—possibly called the crank register or pilot register—projects too far beyond the flat mounting face of the crank.
The spacer’s center counterbore bottoms out against that raised crank register before the back of the spacer reaches the flat crank flange. This leaves a visible gap between the spacer and crank flange.
The first time I tightened the bolts, I didn’t realize the spacer was bottomed out in the center, and tightening it broke the spacer. Obviously, I will not try pulling another spacer down with the bolts.
What I cannot understand is how this crank can have what appears to be a recessed flexplate-mounting flange but an abnormally long center pilot/register. The spacer is supposed to sit flat against the crank flange, but the center register prevents it from doing so.
Has anyone encountered this before?
Could this be:
An unusual or different crankshaft installed in the LQ4?
An existing pilot adapter or sleeve stuck on the crank?
The wrong crank spacer or an incorrectly machined spacer?
A crank that has somehow been modified?
A different engine/crank configuration than I think I have?
The original reason my converter pilot appeared to bottom out with the dished 4L60E flexplate?
I have pictures showing the crank, the spacer sitting against the center register with a gap behind it, and the spacer installed from the front.
I’m going to measure:
Crank-flange mounting face to the end of the center register
Depth of the spacer’s rear counterbore
Outside diameter of the crank register
Inside diameter of the spacer counterbore
Crank-flange position relative to the rear bellhousing surface of the block
Any ideas about what I’m looking at or which measurements/specifications I should compare would be greatly appreciated.

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