I just picked up this motor and I don't know what this hole is for. It's right above the spark plugs, one on each housing. Theres cracks around it and I don't know if I should worry about them. They don't go into the threads and stick out so I don't know for sure if there actual cracks or not. Thanks for the help.

 

That's the hole for the knock sensor. Not sure if the cracks are okay or not.

 

Theres one for each rotor? Thanks for the help.

 

you only need the knock sensor if its a turbo though.

 

And it's only on the front rotor housing

 

on a s4 , my s5 block has it in the middle plate

 

It's a turbo. And it's on both housings. Did this guy seriously sell me a motor with two front housings?

 

Those cracks would just be casting marks. People think there front covers are cracked all the time but are just casting marks. Who knows, maybe it was a rebuilt motor and they replaced the rear housing. Sure does look nice though!

 

So it's ok to have 2 fronts? I don't see why not. Yeah I was kind of thinking it might be something like that. Or maybe just a coating cracking. And thanks I've been spending a lot of time cleaning it up.

 

its ok to have 2 fronts. Good luck with everything.

 

Thanks man I'm going to need it! It's my first swap and I'm putting an s5 into an s4 so it should be.....interesting.

 

It's nothing man. Well if you dint have to deal with emmissions it's even easier. Just make sure you use all s4 electronics. And either swap your front cover or run premix.

 

Just in case you don't know exactly what you need then read this

http://www.rotaryresurrection.com/2n...o_s4_swap.html

 

I had another thread about the swap. Someone else sent me that same link. I think it might of been you. lol

 

lmfao, awesome. Good luck.

 

the blue and silver tag near the CAS indicates that the engine was a mazda rebuild at one time. probably a nice low mileage engine.

 

I have an S5 non-turbo block in my car, both are REAR housins (R stamped on top), & both have knock sensors. I think whoever did the castings in the 80s/90s of these housings used the same base mold, so front & rear have knock sensor holes

 

Can that tag also be a sticker that looks just like that? My S4 n/a engine has the same thing but its a sticker thats worn out. I always thought mine was rebuilt before.

 

Yep it's the rebuild badge. Motors only got 13,000 miles on it I'm told.

 

This is exactly what they are. Actually, they're marks from cracks in the steel mold they use to make the housings.

The only thing to worry about concerning using two front or rear housings is the bypass air hole drilled in the exhaust pasage. It is the only reason there is an
"F" and "R" stamped on the housings. Everything else is the same. The rear has the hole to the front and the front has it to the rear so they can each pick up exhaust gases coming through the center plate.

Of course, if you have blocked off everything and aren't using emmisions, then it doesn't matter.