Is there a difference from the front housing vs the rear housing other than one is stamped F and the other R.

I was told there was because of the EGR ports, but I can't see any differences at all between the two housings.

Does it really matter when rebuilding an engine.

I have three motors and out of the three we were able to salvage 2 good housings. They were both stamped "F" for front. So we used them. Now I've been told they will work but may not pass emmisions.

We have the core ready for all the intake part to be mounted, but we stoped to verify incase I have to hunt for a rear housing.

The motor is going into a 90GXL N/A. 5 speed

Please comment your facts not your opinion.
So only engine rebuilders with experiene please respond.

 

Take a air gun and blow thorugh every hole - what you will find is they are the same. At one time they were different. I believe mazda just added the extra hole to make them universal.

I have a stack of each (S5's)in my scrap pile. I spent a sunday afternoon (a long time ago) looking for that difference - never found it.

 

WE did the same thing at the exhaust port but could not find a difference. The parts manual does show different part numbers but that could be because they stamp "F" and "R"..

We just need this to pass emisions

 

Yes, the EGR ports are mirror imaged between the two. It took me a while to find it, too, and that is the only difference I found after a good bit of investigation...

This was on two new housings...

 

FYI
There is definately no difference on our 90GXL N/A. Both housing were stamped as F (front housing) We have >600 miles after the rebuild and it passed Mo state emissions test with way below standard levels. We installed a Racingbeat Header and a hi flow cat with Apex N2 dual cat backs. I was surprised when it passed with such low level emissions.

Note: everthing in the engine bay was put back in stock form other than the header.