OK, so here's the problem. I've only ever found a smallport 4A-GE once in my area, and that was over a year ago. At the time I didn't want the complete swap so I pulled the head, dizzy, ECU, intake, exhaust, and most of the connectors. But I didn't get the AFM since my plan has always been to go standalone. Now I have a bigport RWD 4A-GE, about 99% complete, including the AFM. Can I wire up the bigport AFM to the smallport ECU? I'd hate to hack up the RWD GT-S harness I have just for that damn AFM. If I could buy that AFM plug w/ wires somewhere, that would be better since I'd have to piece together a custom harness anyway. Or can I pull an AFM from a junkyard donor (other than a 90-91 GT-S or 90-92 Prizm GSi) and wire that in? I would already have to make up my own harness. Hell I still need a 12p connector for the ECU because I somehow forgot to get that from the Geo Prizm GSi.

Another question I have is about compression. Long story short I can't use the 4A-GE block I have because of my transfer case (AE95). So I was thinking about using my 4A-FE block and crank (cast instead of forged, I know) and the bigport pistons and rods (40/18) under the smallport head. I don't have a 42/20 crank or rods so I can't just get smallport pistons. What kind of compression would I get using those 9.4:1 pistons with a 7A-FE head gasket? Is that even advisable without having the block & head cleaned/resurfaced?

I think you can use the large port afm as long as it comes from the 88 - 89 corolla gts. according to toyodiy it says they use the same afm. as for the large port from the ae86 im not sure about how it will work with the small port ecu :/

about using the 4af block, it will work. you should check the 4af crank as it might be a 42/20 and therefore be able to use your small port rods and pistons. also check to see if you can use the 4af rods with your high comp pistons. if you want to use the 9.4 pistons your compression with the 7af gasket will be about 9.7 - 9.9:1 comp ratio with no milling to the head or block. you can go with out milling if your head and block deck are not warped or scared. iv done it. just make sure you have a clean mating surface and use new gaskets

Any AFM from the 88 ae92 and up should work correctly, the only thing is that the smallport uses a knock sensor and 4 wire o2 sensor. If the 4a block that you are using has a place for the knock sensor then you are good. I think at one time I used the blue top AFM and the engine ran fine, give it a shot to see what happends, i think that atleast if all the pins are in the correct order the AFM should work, same voltage signal and sweep range.

OK, thanks! I'm debating whether to do this. 4A-FE is just so weak. ~30 HP gain would be nice.

At least one of my 4A-FE blocks ('97) has the threaded hole for the knock sensor. Not sure about my '88 block.

I don't have smallport rods / pistons or 42mm crank. That's part of my problem, I wasn't smart enough to pull the complete smallport swap, just the head 'Course I also went alone to the junkyard so it's not as though I was going to heft that engine around by myself.