Ok... this is going to sound a bit wierd, but here goes. For background, look up my 4age 20v MG Midget in readers rides.
I had an issue with a remote oil filter adaptor (cheapy aluminum one) when I moved from CA to HI which destroyed the crank and a rod. I rebuilt the engine (no small feat with a JDM only engine) and it worked great. Changed the oil filter adaptor for a canton billet piece and no more problems. Low(er) oil pressure when hot, but didn't chalk that up to much (slightly less than 20 at idle, but right up to 50 once above 1500). All is well for two years. I ride it out to "cars and coffee" in Great Falls, VA on the wrong day last weekend (Sunday vice Saturday), and I get a noise above 4k on acceleration. Oil gets hot(ter) and now its all the time, except at very low rpms.
I'm thinking main bearings, but I haven't done a lot of diagnosis. Imagine an ostrich, head planted in sand. That's where I'm at now.
So back to the thread title: the transmission has always leaked and is a bit weak for the plans I want (~220hp turbo setup). Original plan was to adapt the miata trans to the 4age, but with that on the outs... why not just put a '99 1.8 in there and modify the ppf to meet the miata-based independent rear I've got? I've found two different motor/trans sets for $799/$899 respectively.
Is this (any more) stupid (than what I've already done)? I figure the engine mounts were the easy part... get an ebay turbo manifold, .... how much work can it be to (re)convert to another engine? Would have loved to go S2k, but those are still $4k++ and my budget to start is $1k+ turbo stuff as I go.
ca18de 
for a 200 hp goal with turbo even the 1.6 is capable, but there si no replacment for displacement so why not go for the newer 2.0? cost? the ca 18det is in your range
If you're worried about cost, look at a 1994-97 engine instead. They're less valuable and you can stick that '99 head on later if you want. The 94-97 engine also has a lower intake manifold, which can be useful in tight quarters. But if you can get an engine and trans for $800, that's a good deal.
It's easy to mount a Miata transmission like a normal trans. The PPF is a cool thing, but not magical and it can be replaced.
Thanks guys. Evil- don't know much about the ca18, but I like the availability and excellent transmission attached to the miata 1.8.
Keith, will look for a 94-97, as that low intake manifold will help with hood clearance. Sort of a bummer to re do my re do, but this might work out best in the end. Unless I trip over an S2k engine. WRT the PPF, I think it still might be the easiest method to locate the diff nose. Now I have it located with a boxed in section for the bolt holes and a massive u-bolt for extra security across the nose. Oakey, I know, but it works. Might be more elegant with a modified ppf.
Might want to keep in mind, turbo kits for the 1.6 flavor of the engine are pretty cheap. We just picked up a Greddy kit for $300, without any frills.
If you do go with the 1.8, make sure you grab the oil sending unit from an earlier 1.6, for a proper oil press. sending unit.
It's too bad you're not closer to florida. I have an extra block sitting in my garage.
-meaty
It's actually going into the MG, which has a mechanical Smith's oil pressure gauge, so I think the only challenge there might be getting the adaptor fitting to fit the 4an female fitting I've got sorted now.
Are 1.8 turbo kits more expensive than 1.6?
Teh E36 M3 wrote:
It's actually going into the MG, which has a mechanical Smith's oil pressure gauge, so I think the only challenge there might be getting the adaptor fitting to fit the 4an female fitting I've got sorted now.
Are 1.8 turbo kits more expensive than 1.6?
Yes, but only because GReddy (the cheapest offering) only makes a kit for the 1.6. Once you start looking at higher end kits, the cost is pretty much a wash.
We have all the parts you need for a -4 AN fitting for oil pressure. No problem there.
The 1.6 is physically smaller by an inch or so in all dimensions, that's a good thing for Midget builders. As for the availability of cheap turbo kits, I think the GReddy is out of production so there's no real advantage between the 1.6 and 1.8 in terms of turbo cost anymore. Besides, given the unique chassis, you'll probably only really need the manifold and a turbine outlet and there are several sources for those. I know one 
Everything else will have to be built for your application.
If you do get a GReddy manifold, be sure to put some cuts in the flange for expansion or it will crack.
