Can I bolt an older (pre 1990) Bravo lower to a newer (post 1995) Bravo upper? The only real difference I can see is an oil hole in the newer drive. Thing is, some of the IMCO lowers have this oil hole blocked.
So, can I run an older lower with a newer upper?
Can I also do this visa-versa? (newer lower W/older upper)?
Thanks,
Gordo

Also,
I have seen a newer "replacement" lower that had the "boss" for this oil hole, but the hole was not there.
Can I drill out this oil hole to use with newer upper? Do I even need to?

I don't think so,the old bravo upper has a oil vent hole in top cap and fill hole in the side where its normally vented. As far as I know if you put a new upper on a old lower no oil could get to the top from the bottom and it would melt down because there would be no oil passage between the two. I have a old style upper in real good shape with good looking gears and bearings I'd like to sell if anyones interested,Smitty

You can put an newer lower on an older upper. Simply put a plug in the extra oil in the newer lower. I've run one that way for 2 years.

I've done this too with no problems.

What does that hole connecting the upper to the lower do,allow oil to drain back,let oil from churning in lower pump to the top or is it a vent? I have a nice early upper I just could have sold a few days ago to a friend but didn't think it would work,at least I know now though,Smitty

Thanks Payton.
Now, is it possible to run a newer upper with older, (non oiler) lower if I simply plug the upper hole?

no you can not run newer with older its an oil hole and provides improved oil circulation on the drive which inturn lets them run cooler I wouldnt recomend "plugging it" to anyone bravos need all the help that they can get

So heres the big question,once you've plugged the new style lower and bolted a old style upper on it would the drive work exactly like a old style upper and lower (no better/no worse than what pre-91 bravos came from the factory like),just without the extra cooling a newer one would have OR would it create a new problem,Smitty

That is what I was told by the company that I bought my new style lowers from. They are known for doing performance upgrades on Bravos. The lowers I bought had been replaced with some shorties.

GOODT tell me if I was told wrong. And how can it be fixed?