Gsl-Se Center Iron vs. 12a Center

[TheDriver216]

Im deciding on which way to go with a project and was wondering which Iron has more material that can be ported.. I was informed that the 12a iron can be ported farther then the Se.. any truth to this?

I want to use the Se center in a turbo Efi app and use teh Se injector bungs for my primaries and a throttle body injection for my secondaries.

Thoughts on which can be ported bigger would be greatly appreciated.

Build thread to come soon!

[Whizbang]

well if we break down that GSLSE motor tomorrow we can probably compare to the 12a visually. Not going to cut them in half though...

[TheDriver216]

Awww man, i thought thats what you bought the chop saw for?

[Whizbang]

if we had another 12a center plate and a BAD gslse center iron, that would be another matter.

[Rogue_Wulff]

As a general rule, most 6 port center irons have less available area for porting than the 4 port center irons. If you look at the 6 port center iron, and compare the stock ports to a 4 port iron, you would see the 4 port has larger ports to start with. This tends to support the idea that a 4p center can be ported more, since there was less casting needed around the ports on a 6p center.
This is not a "Hard" rule, but is the general findings of many engine builders. Even RB makes mention of this on their website, in the porting area.
It is entirely possible that *some* 6p center irons can be ported to the same extent as a 4p center, but most cannot. The 6p center didn't need the ports to be as large, since the secondaries were so much larger total area compared to stock 4p secondaries. This also allowed for an improved idle quality on the 6p engines, in spite of the more aggressive overall port design, and resulting higher HP.

[el canito rotary]

what i did with mi engine ihave gslse iron plates, i use 3 12a plate and i did a agresive street port and i use 13b housing and rotors and a 600 holley, is work pretty good so far

[PercentSevenC]

12A intermediate plates have much more porting potential than -SE plates. Only use the -SE plates if you want the injector bungs.

[RotaryProphet]

The route to go would be to either have someone with a mill machine some injector bungs into your 12a center housing, or weld some bungs onto your intake manifold.

Like I told you when you were going to buy that center housing off me, there's definitely more horsepower potential in the 12a center.

[Rogue_Wulff]

Just how much more power can be made with a 6 port 13B, using a 12A center iron? I know there isn't much to be gained by porting the end plates, but does the 12A center iron give a real power advantage?
I have a SE 6 port converted to 4bbl carb. I have no plans to rebuild it currently, but as we all know, that could change anytime since the engine has over 200K on it. I figure on doing the porting, and swapping the center iron, when the time comes. I wonder what kind of HP numbers could come from this type of hybrid?

[BigTeddy]

Mira loco...

I have gsl-se housing witht he exhaust sleeves taken out, and im running front middle and rear 12a irons ported the only thing is you have to get the racing beat holley intake mani for this setup...

And in all honest im running all motor to break in my motor running a 600 cfm holley im pushing in the ball park of 290-300 un-tunned...

http://i101.photobucket.com/albums/m76/teddyrx2/100_5214.jpg

[Whizbang]

what porting?

[BigTeddy]

huge street ports on the plates and huge bridges ports

[Jeff20B]

I'd only recommend a GSL-SE plate if you were EFI so the primary injectors have enough velocity to work heap big. Otherwise with a carb, use a Y plate. What you lack in low RPM veloctiy, you make up for with midrange power. Add porting and power goes up. You can't really port the SE plates much.

[Rogue_Wulff]

Jeff, any idea of how much more power can be made by swapping the center iron, and porting, vs just porting the 6p to the max that it can go?
If I ever crack open the SE engine, I plan to swap the center iron. Though, that would leave me with a totally cool looking injector blockoff, and no where to use it..... I dunno who made it, but it has the piston with a circle/slashed across the middle logo etched into it. Very noticable under the hood.

[Jeff20B]

Maybe somebody could use it. Someone like me who would like to use a GSL-SE plate in a 6 port 12A, which would be a nice port size increase over stock, but Y ports would be too big. I do have a basic injector blockoff already though.

Atkins probably made it. The design sounds familier.

[BigTeddy]

I'd only recommend a GSL-SE plate if you were EFI so the primary injectors have enough velocity to work heap big. Otherwise with a carb, use a Y plate. What you lack in low RPM veloctiy, you make up for with midrange power. Add porting and power goes up. You can't really port the SE plates much.

Jeff is right...the only advantage of using the gsl-se plate is for the use of fuel injectors...

Not much porting can be done to the gsl-se irons...

[Rogue_Wulff]

Yeah, I am aware that the stock 12A primary ports are larger than what can be achieved on a 6 port center iron. Simply swapping the center iron for a 4 port, on an otherwise stock 6 port, gives the same benefits as porting, but even more than what can be got from porting the 6 port center.
With a moderate to large SP on the 4 port center, and the limited porting available on the 6 port end irons, combined with exhaust porting, one *should* be able to make even more power than a "Monster SP" on a 4 port, since the secondary ports of a 4 port cannot achieve the size of the 6 port.
This is my plan, should I ever open up my SE 6 port. I already have a RB holley style intake for the 6 port, so I will use it on the "Hybrid" 6 port. To convert to a 4 port 13B would require the purchase of a different intake, and I'd rather not have to do that. The 4 bbl carb also helps the idle quality on a 6 port, since the aux ports have the sleeves removed to use this style intake. With a big 2 bbl, it is idling off both the primary and secondary ports, but with the 4 bbl, only the primary ports are utilized at idle, unless the intake has been modified or an open spacer is used.

I'm just curious as to what kind of power is realisticly achievable thru the "Hybrid" 6 port, using a 4 port center iron, along with moderate porting. By moderate, I mean something still street freindly, that really comes alive when the loud pedal is depressed....
Of course, the stock 6 port with the RB intake and 600 edelbrock is already a HUGE improvement over my SP (mild) 12A with stock intake/carb.
BTW, I also have a 650 Holley DP for the 13B, but haven't tried it yet. I might even go blow-thru, once I have the "Hybrid" 6 port built and broken in.

[Jeff20B]

Wulff, you may be in danger of having too much port area if you streetport the Y intermediate. Heck you may have too much just with a stock ported Y.

I basically suck at math but I know rotarygod ran the numbers for 6 port intakes and discovered that there is a happy ratio between total port area and total flow capability of the stock intake manifolds, resulting in a little bit of natural supercharging. The RX-8 is basically perfect in port area and total manifold CFM, and that's why it has so much all around good drivability.

If you're up for a little experimenting, I'd like to recommend a course of action for you. If your current setup is pretty well dialed in and you know its quirks etc, it would be very educational to swap in a non ported Y plate and see how it changes things. Then at some later point you could do a port job on the Y and see whether it increases power or decreases. Be sure to get dyno runs as well as daily driving in on it. Then we'd have a body of information to show others contemplating bigger ports on a 6 port, and whether to recommend against it.

[Rogue_Wulff]

Jeff, You bring up some valid points.
My actual plan, is to swap the 13B in place of the 12A, since the 12A has oil control ring issues. This 12A would then be set aside, as a "backup" engine, in case the 13B gives up on me.
As i have time, and funds, I had planned to freshen up the 12A, then reinstall it, and freshen up the 13B. During the 13B rebuild, swapping the center iron, and mild porting is planned. I doubt I would go very radical on the porting, unless the 12A really worked well for the daily driver. Any radical ported engine would likely find a home in my SE chassis, and relegated to use as a weekend toy/track car/autox car.
The SE needs more suspension attention than I really want to do, before it can see action as the primary autox car next season, and the 12A car has coilovers and other goodies, but a smoking issue.

As for doing multiple porting/builds, I'd rather avoid doing that, as my shop time is not easy to acquire. I hate not having my own shop/garage to work in.

[BigTeddy]

Okay hold on guys I'm a little lost in what your talking about? Are you guys talking about the divided section on the 6 ports plates on the end irons? If so, it has been done...I got a motor sitting here in my garage with the divided port taken out and ported all the way through making it one huge port...

And might i add it was a hell of difference in performance, airflow, and just over all performance of the car and motor... Lots of tunning and hours went into it running the holley 675 avenger carb, but in the end was well worth it...

[Rogue_Wulff]

Nope. We're talking about the center iron.

[BigTeddy]

lol...okay now i follow...

[scarsofcarma]

Cool thread! It never occured to me I could use 12A irons w/13B housings... I think I am going to try this at some point. :D