Is the block to transmission bell housing plate necessary (the large metal plate)? Obviously it helps keep the bellhousing free of water/debris etc. but other than that is it truly necessary for any other reason?

1.8 mated to a 6 speed.

I am a moron and forgot to install it before I put everything back together. Just realized it and I have everything together ready for first startup on my new build.

Since I am this far I would like to do a first startup/motor break in and make sure everything works before I rip it all out again. Just want to make sure this will not be a serious issue for a Break in drive?

 

Most people are going to say yes, myself included.

Have i ran without one for years? Yes.

Can it cause issues, also yes.

 

If memory serves, that plate holds the dipstick tube fastener and the mounting point for the ground strap by the brake booster. Might need those, or at least accommodate for em.

 

Should be OK for a break in drive, so long as it is not wet out.
It is a dust shield primarily, the lack of small spacing it creates should not cause a problem with the input shaft/pilot bearing mating.
Long term dirt and dust and water would be more of a problem if you keep it that way.

You could try cutting up the shield in two parts, removing the starter, pulling/prying the Trans part way back and inserting it when you do put it in, rather than a full disassembly. I have done that after the same mistake.
Once the trans is bolted back up it stays where it belongs.

 

I like this idea. I had also thought of that, but was a bit worried about it possibly moving around enough to rub the flywheel? Sounds like it is rigid enough to avoid those issues though.

 

There are two dowels from the block that mate with the transmission, and a circular hole in the plate for the starter. Plus circular hole for everywhere the bolts go through.
If you do this the real challenge is pulling the trans back far enough to clear the dowels, without completely un-mating it from the clutch and having to spend all the time re-engaging it and wrestling it back on.
But once the trans is back in place and a bolt or two is partially, the dust shield is not going anywhere.

I cut it at the bottom and the top, into two roughly symmetric pieces, so both has a dowel to position it before it goes fully together.

 

I have a tip for this problem...
If I have to change a flex plate on a V8 rear drive (usually a truck) I will use 2 very long bolts in the 2 lower bell housing positions to hold the tranny up while I move it back the 4-6" I need to access the flex plate.
It's a bunch quicker this way.
This would work OK for this issue. You would have to remove each side individually to slide the 1/2 plate pieces in but It might reduce tranny wrestling.
You would not need super long bolts if you were just trying to clear the alignment dowels. The stock ones might be long enough for this.