I HAVE alredy buy a 13bt s5 engine complet and I have rx7 fd3s
but my problem is the rear rotor housing and rotor is scratched,
my question is:

can I use the 13bt s5 blocks directly in my fd, I KNOW the mounting is not like fd, i want to take only the fd rear housing and front cover from fd3s and compined to the s5 block? can I ?

 

You can install any engine into any car, but it is going to cost you more time and money then just buying an FD engine. Nothing is compatible, from the oil pan to the intake manifolds, nothing will bolt to the FC block. Then the motor mount locations are drastically different.

 

The rotor housings can be used but you'll have to get the coolant passages blocked off somehow. On the fc engine go to the lower intake, the fd does not have coolant passages there at all.

 

Ok thank you
I know about the coolant but can i combine
1- the fd rear housing to rear fc rotor housing
and2- front cover from fd to front fc rotor housing because the interior of fc best than my fd is blown rotors and apex seals

 

If you are asking if you can mix irons, the answer is No. The intake runners are at different heights on the engine.

 

If you're just asking if you can use FC rotor housings in your FD build, then you can but you'll need to block off the coolant passages as has already been mentioned.

Pretty sure he is re-using his FD irons..... sucks to blow an engine in Kuwait, I've spent time there and it gives new meaning to the term 'desolate'

 

Right