1st Gen 13b into a 2nd gen...?
 

hi, i am very new to the rotary scene and i dont have that much knowledge about them...i recently picked up a rx7 s4 fc and the motor blew a water seal, now i need to replace the motor...i was looking around for a good used one and ill i can really find is 13b off of a 1st gen rx7...so my qustion is, can i put a 1st gen 13b short block into an fc (swapping out all the necessary parts)?

The short answer is no.

You'd have to do a lot of work and spend a good deal of money to be able to get the 13b from the first gen. to run in the second gen. With the money you'd spend doing that you might as well get the engine thats blown in your second gen. rebuilt.

the 13b from the gslse is mounted off the front cover. fc mounts from the sides of the block. it probably can be done, but with alot of fab work. can't use the fc intake so don't know how the fc ecu would work with the se intake and i'm sure all the sensors will be different. more of a headache than rebuilding urs, and would be cheaper.

i'll put this out there, but unfortunately i'm not home to confirm each detail on my SE engine. most of this is from memory, so bear with me.

if i'm not mistaken, the SE engine is equipped to mount from the intermediate housing, like the Gen II engines - it's just that they were never needed for the Gen I. :) i never pulled my oil pan, so i'm not 100% positive, about the passenger side, but i'm pretty sure. i am positive about the driver's side though. it "should" just be a matter of bolting on the mount brackets.

it's been several years, but if i recall, the front covers have a slightly different shape and bolt pattern, so in order to mount the Gen II oil pan, you'd need the Gen II front cover (and of course, the pickup tube). the next issue would be swapping over the intake manifold because the SE did not have secondaries.

all in all, i've never had to go SE-to-FC, but when i did FC-to-FB the first time, i learned what bolted up and waht didn't. it really shouldn't be all that bad. if you're in a pinch, i'd say go for it, but if you have the luxury of waiting or if you don't feel like you're up to it, i'd say wait for a proper S4 engine. if you have any plans to keep the car for a long time, you may be better served just rebuilding your old engine, especially if the SE engine you speak of is unknown to you.

thanks everyone, i really appreciate all ur post...ive learned something new ^_^...but ill take ur advice diabolic...ill jus wait around for a proper s4 motor...but as for rebuilding it...i read that if ur water seal goes bad and u decide to let ur car set for awhile (which i did)..the internals get rusted, which will conclude to replacing it because it will no longer be rebuildable...so im left without a choice to getting another motor...=(

what you read is not true in all cases. there are a few variables involved - certainly enough for me to say not to condemn the engine until you see it for yourself. you won't know what's what until you pull it apart, clean and inspect everything.

If I remember right the water seal is the equivalent of blowing the head gasket on a piston engine, its the outer most seal on the housings. The internals would rust more if all of the fluids were left in the engine vs. the water seal going bad, I think. I'm sure that if some parts were rusted internally there would still be salvagable parts too. If you buy a used engine who's to say that there isn't something wrong with that engine either like low compression, blown seals, etc.