You all have prob been over this several times but I couldn't find it........so what is the deal with everyone sayind to go 13b 4-port with a street port.....I have an 84 SE with the 13b 6-port and I'm getting it rebuilt with a heavy street port......Are you not supposed to port the 6-port 13b???

 

I also have a 85 SE and used to wonder the same thing. The 4 port 13b's are the older (pre-7)rotarys and had 4 ports as opposed to 6.. Everything Ive seen doesnt really seem to encourage porting the 6 ports because of the closeness to the coolant jacket and apparently it wouldnt make the huge diff it does in a 12a. When I rebuild my 13b (I now have 2 SE's and 1 spare engine) if I have a bad housing I may look into any templates out there and take a stab at it with a junker. Now we patiently wait for any errors I made to be corrected by the people you really want to answer your questions!

-Erik

 

If you're keeping it N/A I don't see why you wouldn't use the 6ports, they have considerably more intake timing than the 4 ports.

 

You can port them. You can also bridgeport the aux ports only and keep your idle and low end torque. You may need to upgrade your injectors and add fuel only management, SAFC etc. Street port the primaries and secondaries, bp the aux, could be fun.

 

You'll get much more worthwhile practice in, if you practice on an iron (where the intake ports are) as opposed to a housing (where the exhaust ports are)

You won't be able to perform as drastic of a street port on a 6port as you could on a four port. But if you're rebuilding anyway, it is deffenatly worth your while.

 

Again, I don't understand that. The primarys can be made equally as large, and the secondary/aux have more port timing than you can get out of a 4port. In terms of size, the 6ports will allow more.

 

Say I went with just the heavy sp......I am planning on getting my injectors cleaned......instead of getting them cleaned should I upgrade them?? This is just with the heavy sp though......and what about the fuel only managament?? Is there anything else I should be upgrading???

 

N/A...?.?.?. I still haven't figured out what that means yet......haha.....is it non-turbo??.....that would be my guess

 

N/A means naturally aspirated, pretty much non-turbo and non-supercharged.

 

I have always been told otherwise. Watter jacket clearance issues blah blah ect.

I could very well be wrong. I hope I am.

But every engine builder I've ever talked to, and everyone else on this forum has led me to believe that a 6p can not be street ported to the same extent as a four.

 

The primary plates are the same, so I know those can be ported equally (although the castings had different port timings, they can be ported identical). The secondary ports is what would be in question, the aux port bowl doesn't need to be made any deeper, just additional port timing can be added (and smoothing). I think you'll run into the waterjacket sooner if you try to make a deeper bowl on the secondary port sooner than a 4port, but I'd believe the additional timing makes up for that lack of additional volume.

 

Interesting.

Atkins ported my motor. I wonder what all they did

 

I've seen both styles make equal ammounts of power, (190rwhp range), so they both work well, I just think theres some more potential with the 6port irons though.

 

ok.....atkins told me that a 13b 6-port rebuilt and street ported with header and exhaust will give me around 200hp.........the rotary warehouse told me it would give me around 170.......which 1 is it???

 

If you stay with the sp, the injectors may handle it, but keep in mind the 2nd gens have 4-460cc injectors, which should be good to 200hp. The SE's have 2 680cc injectors.

I'm not claiming to know what you need, but it's something you might want to check out.

 

You'll definatly want 4 injectors, and either an aftermarket ECU or a 2nd gen ECU.

I would guesstimate an atkins port to net around 170rwhp.

 

Ok, here goes...

When porting a 4 port engine, you are mainly adding port timing, both on primaries and secondaries. If you are good at porting, you will have a slight benefit from shaping the port runner well.

The primaries are MUCH larger on the pre 86 4 port engines as opposed to the primaries on the 6 port engines AND there is alot that can be ported out from them. In fact, they are identical to the 4 port secondaries. The 6 port primaries are small and there is not much that can be ported from them in comparison but it is still definately worth doing. The benefit to the 6 port center housing is the provisions for fuel injectors. For this reason I am using a GSL-SE center housing on the 12A that I am building.

When streetporting 6 port engines you are not adding much port timing to the secondaries and auxiliaries (if you know what you are doing). You are mainly improving the flow of air into the engine, specifically through the auxiliary ports. The primaries do add about 10-15 later closing when streetporting versus 20-25 for the 4 port primaries (both have the same opening and closing duration stock).


4 port streetporting in progress pictures (center housing from 6 port GSL-SE because of injector provisions) Look on page three

http://community.webshots.com/album/374839276FEScYG

6 port streetporting in progress pictures. The engine is a 1991 NA engine.

http://community.webshots.com/album/527175054lXOfxX

 

The port timing on the primary is quite different stock (for s4/s5 turbo to n/a), but their cast the same, they can be ported identically. The only difference is the secondary/aux versus the turbo secondary (on a 4port). Unless you're using early 4 port irons, then the limits are quite different, however I don't believe even those can be ported to exceed the 6ports port timing on the aux/secondary.

N/A - 32/45
TII - 45/50

 

i was thinking about doin a aux bridge so when i move to cali i can still pass emissions ( soory to high jack) but i need a template and would the stock amf handle that amout of air flow w/o it choking out. i think that Rx7Carl flow tested it at 352 cfm would that be enough?

 

The early style 4 port primaries casting is WAY different than ANY 6 port casting, GSL-SE or FC. The TII irons do have the same casting as the 86-91 NA center housings but since he has a GSL-SE none of this matters because the irons are not interchageable between pre 86 and 86-up. This is coming from someone (me) who has ported various housings from different years. You don't need the extremely late port closing on a 4 port because the ports don't have all of the restriction like the 6 port housings. Stock 4 port closing is 40 degrees, both primaries and secondaries. Stock GSL-SE auxiliary closing is 70 degrees. A large streetport can delay the port closing to about 65-70 degrees on a 4 port IF YOU KNOW HOW TO SHAPE THE PORT SO THAT YOU DON'T BREAK INTO THE WATER JACKET. Racing Beat's template closes at 60 degrees and is plenty. There are people making considerably more than 200 flywheel horsepower on an old style 4 port 13B with Racing Beat's template.

FYI, my ports on the 12A close at around 50 degrees ATDC and the ports are my own design. Please do not try to port your first engine without using a template, It is easy to port into an area should not be ported if you are not familiar with porting a rotary and this can ruin the housing and possibly more of the engine if you try to run it.

 

So what your saying is that if your looking for N/A RPM, go 6-Port. If your looking for FLOW N/A, go 4-port?


I've always considered doing a 6-Port N/A Build. I would Bridge Port the Primaries (Center Plate) and Street Port the secondaries (End Plates).


How do you think that would hold up? What kinda numbers would it turn. Would it be better to use a 12A Centerplate for more Flow because the runners are larger? (Im all about carbs. No EFI here. I wont miss the Injector holes.)

 

You might wanna check out the SE forum as well. I know some people down there that have bridgeported six port motors with holley carbs. I know one in particular that run 10's consistently at the track on a 6 port bridge with I think it was 150 shot or nitrous in a datsun 1200 for few years now.

 

i bet hes in good ol FL i check it out bc i really would like to bridge the aux ports i just dont know the basics to design my own bridge if i cant a tempplate for it.

 

Summary:

The 6 port engine will give a broader torque curve if you use the acutators. If you are running a Holley (not my choice of fuel delivery but that is another debate), you MUST get rid of the auxiliary port acutators and run them open regardless. So, if you plan on going carb with a streetport, use a 4 port engine.

The 4 port engine will net a little bit more power when streetporting.

Both of the engines that I pictured earlier will be run with standalone engine management. If you are set on running a carb and distributor, I like the Weber DCOE/Mikuni sidedraft but for the money that you will spend on the carb, any parts that you may need, and the costly jets that you will need to switch you are better off going with Megasquirt EFI.

 

If I were to switch to a carb'd 13b 6 port from the efi I would go with a 12a streetported centerplate, streetport the secondaries and street & bridge functioning 5th&6th ports with a side draft intake (there was one that fit on the 13b lower intake). Here's a pic of the template over my stock ports.