In case you don't know form my other posts, I'm going to be rebuilding my engine in the near future and I'm trying to get everything sorted out now so I know what to buy/get.
First of all, last time my engine was rebuilt, I was told by the first rebuilder that TII center irons would give me more power because the ports are bigger. Is this true, or BS? And if it is true, would it give me more high-end power at the expense of low-end power?
Second, what are the differeneces between s4 and s5 irons? I have a friend who is putting a v8 in his low milage s5 and he is probably going to give me the engine. I have no idea what condition mine are in, but I'm expecting the worst. I think the port openings going to the LIM might be different sizes, but I'm not sure about other differences.
Thanks in advance.

 

so do you want to use series 5 irons with series 4 rotating assembly?

 

the only thing I have ever found is the front irons have a different milled area for an oil o-ring. Mazdatrix has a complete write-up pointing out the two and how to avoid loosing the o-ring after rebuilds. Once you read it you'll be able to identify the two different ones.

dDub also had something on his web page.

if you install the oil o-ring incorrectly or use the S5 o-ring on an S4 iron. The o-ring can move and cause you to have low oil pressure for a seemingly unknown reason.

 

Actually I plan on using s5 rotors and was wondering about the irons in case mine were toast.

 

T2 irons are 4 port and n/a irons are 6 port so unless you do a full conversion it won't work. the T2 middle iron does have a slightly larger port, the difference is a tradeoff of low end torque for upper end power but the differences should be slight.

it wasn't said if it was a turbo motor but the only difference in n/a is like Jhammons said, the front cover o-ring milling is slightly deeper on an s5.

 

Its an NA motor. So I guess I'll just stick with what I have. It only ran with a popped seal for about 3 seconds, so hopefully the irons are fine. I'm planning on just buying new rotor housings. I'm prob going to get TII housings so they are easier to port and Ill just plug the coolant hole.

 

you can use the irons, just use a slightly thicker o-ring for the oil pump feed line seal. with this setup you will have no EGR though and the EGR passage below the intake ports on the middle T2 iron will need to be sealed.

 

Well, this was mainly a just in case question. Its also a last ditch effort because my current irons have a street port.
Also, thank you very much for mentioning the front seal problem. I just read the page on the mazdatrix website and it was very good info, as I prob would have done it the wrong way. That also could have been the cause of my oil pressure problem. I had no oil pressure at idle, but I always thought it was a problem with the sender unit. I hope thats not the case because I might have more internal wear than I thought....

 

S5 to S4 - S5 front IRON has a larger front oring casting and S5 front and rear had a larger port runner 1/8in and the port timing opens 10* later. S5 temp sensor hole is larger. S5 rear IRONS some were the same some had triangular reinforcement on the oil pedastool dowl, some had a larger casting same as the REW with the reinforcement.

The TII intermittent Iron P port is much larger then NA it opens earlier and closes later. This will increase top end HP and lower your TQ. However the port runners are identical. If you port the motor this will mean nothing. However if you have a USDM Iron the S4 will have a EGR valve and the S5 will not. The S5 TII wil also have a knock sensor on it.

All Irons are interchangeable though as well as housings.

 

So basically any differences would be negated with porting, correct?

 

Correct.

Should read
The S4 TII will also have a knock sensor on it.

 

what series aside from REW isn't threaded for a knock sensor in the middle iron?

 

S4 is in the INT iron and S5 is on the front.

 

front rotor housing but the middle iron can still accomodate the sensor.

 

Can it? I think I should get me a S5 to take apart :-)

 

I'm trying to use one of my S5 turbo irons in my 86 NA because the original blew a "water jacket rim". I saw a rotary evolution said you just have to seal the bottom EGR passage on the center iron if using the turbo iron. I noticed that they were different in a minute ago after I started taping the stuff up the paint it. I guess I can just stuff some JB Weld down there? Is there anything else that I'm going to run into you is using this iron? I'm using stock (s4 NA) everything else

 

Sorry for the typos, I just had a panic attack! Thanks in advance

 

I stuffed it with red RTV. I hope this is enough..

 

Rtv will probably melt. But only really matters if using stock exhaust manifold.

Either way you shouldn't suffer from an exhaust leak, just a lot of carbon build up in the exhaust manifold to that opening