Drivetrain T5 bellhousing differences: 83-85 vs 86-93

The is more of a general FYI. I don't want to issue a blanket statement based on testing between only 2 samples.

Since I had an 83-85 bell and 86-93 bell, I decided to see what the differences were. There was a lot of statements about the early bells being smaller, or then being the same. Decided to see for myself with the two castings I happened to have.

E3ZR-6394-AA 83-85 T5 v8 bell on left

E6ZR-6394-AA 86-93 t5 v8 bell on right

My method was simple, i rotates the flywheel/clutch assembly around probing to find the tightest spot, and then I used clay to measure.

Parts were a Ford Racing billet flywheel and a FR cobra clutch setup (from the early 2000s). These clutches are notorious for being close, but that doesn’t matter for this test as i'm just measuring distance from pressure plate to bell.

If you search around, there are various threads stating contact between pressure plate and bell in this area depending on what clutch setup is used. The Kink Cobra setup I have was notorious for this as you can see by the very close proximity. I wonder if this adds to the rumors about various bells being "smaller". In my case, it was tight on both year bells.

The test area

Here’s the 86-93 bell.

The initial imprint


Sliced view


Measures about 0.050” clearance

The 83-85 bell

As you can see...same measurement in same spot

So what is the difference? As far as I can tell after searching all over is the lack of this casting boss feature circled here This boss appears to be a vestigal casting feature that would allow an SROD transmission to be bolted up to this bellhousing. Appears that adding this matched the D9 bellhousing.

This could very well just be differences between various foundries churning these out, but it's really the only detail that is notably different on the two bellhousings i have