Ive seen the "rotor housing compatibility" thread.....Im looking for a straight accurate answer, can I use a fc s4 13BT rotor housing with a fd rotor housing? I know about the plug locations diff, but they run the same timing, correct? BDC had success using a s4/s5 rotor housings..........thanks.

-Marc

The ONLY reason i have seen as to why you cannot run s4/s5 housings together is beacuse of the timing. However with the Fd housings I don't know about the timing issue.



Another thing, don't the Fd housings have a different coating on them. Thats why they only needed 2 oil injectors total. But I don't know if that would be that big of a problem.

They worked fine for me, practically speaking, even with lots of power (400+rwhp).



You can also use FD rotor housings but they lack the oil injector up top I think.. Don't quote me on that, though. https://www.nopistons.com/forums/pub...DIR#>/wink.png



B

Yes you can interchange them? are you building a motor for a FC? you can mix and match many parts but you have to becareful about the engine mounts

The "timing issue" is wrong. Changing the spark plug location doesn't change ignition timing; ignition timing is a reference to the eccentric shaft. Moving the spark plug just changes where combustion starts, not when.

The motor i'm running right now in my FC is made up of 1 FD housing and 1 20B housing. Its working fine https://www.nopistons.com/forums/pub...IR#>/smile.png

Yup, the engine is for my FC. FD's run oil injection just on the rotor housings, so that wouldnt be a problem. I actually found two FC rotor housings for sale that according to the seller are sweet. My next question, Walbro 255lph fuel pump, universal from FD to FC?



-Marc

He's talking about exhaust port timing, not ignition timing https://www.nopistons.com/forums/pub...DIR#>/wink.png

Put S4 rotor housings next to S5 rotor housings and you'll see that the exhaust ports are identical; exhaust timing is not any different between the FC series.



What he is referring to is a common misconception about ignition timing... the spark plug location was revised after the S4's, and the spark plugs physically moved in location for the S5's. The altered locationg alters where combustion starts, although many people hold the perception that it alters ignition timing.

I used FD housings in my FC N/A engine. No problems at all. Just check all your tolerances as you would before any rebuild.