12A Street vs 13b 6 Port or 4 Port for race car?
 

I have read several pros and cons of the 12a vs 13b. I am trying to make a decision as to which I'd want to build for a GT1 or GT2 car. What is the difference in dissplacement vs HP gains between the 2? Does the HP gain out do the lighter displacement of the 12A? I also hear of people saying the 12A Street is more reliable? I am trying to decide what to build for my race car. Can use some help and also interested in who are running bridge and periferal port motors?

what are the rules of those classes with regards to the engine?

the difference in size is relatively small and it's due to the fact that the rotors of the 13Bs are 10mm wider than the 12A rotors. so generally speaking, the 13Bs will out muscle the 12As, which should not be a surprise. they are larger after all. keep in mind i'm talking about direct comparisons, meaning stock vs. stock or with the same modifications. i remember back in the day, RB was pretty much pulling an extra 30 to 40 HP over 12As with their 13Bs (again, when everything else was the same except the engine). these days with technology available (fuel injection, ignition parts, engine management, fuels, etc.) i truly have no ideas if that difference holds true any more.

however, 12As are a dying breed now, so it makes sense to me that if you are allowed to work with 13Bs, then they'd be the better choice if for nothing more than they have more available parts - new and used.

as for the 4-port vs. 6-port issue, the 6-port has it's place, but they are somewhat limited. they can be built to run pretty hard, but i've always believed 4-ports to be better all around, particularly if you have real racing in mind.

use the 12A irons, and 13B rotors, and you get 4 port 13B!

the 12A vs 13B thing, the 12A is harder to get parts for. you can argue that the 12A is a little more efficient, but the 13B is bigger, so 13B is more power.

the 86+ 13B's go on a diet too, so there isn't much difference in weight.

Honestly I am a newb and working on a budget to prep my car for road racing. One expert tells me I should do a spec car to start but I don't want that. I know I'm capable of handling a faster class and besides I hear the spec rx-7 first gen class is dying out to the Miata. I am trying to decide the best motor to build for a high rev N/A road race platform. My budget on the motor is around 2k and I already have a nice long block 12A or 13B 6port to choose from

:scratch: How do you know what you can handle? Starting off with a slower "spec" car will teach you more than building a fast car and having HP cover your mistakes. Starting with a SM/ SE30 etc will teach momentum and how to carry speed thru a corner. This will make you much faster once you have a faster car. Honestly $2k engine budget is an IT engine. Need to add some more k's if you want Production or GT engine. Just my 2 cents

FYI- You would need a 20b in GT1. GT2 is probably a P-Port 13b but it's been a while since i read SCCA rules. Also to be competitive you would need a tube frame chassis, Dog ring box, fancy shocks, lots of sticky tires etc... And a budget to piss away
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You're right I can't afford a Gt car. I think I'll be going for a Production/EP1 or 2. That should allow me to do all the mid range tuning and suspension upgrades I want.

I agree with most of this. However I will say the 13BT and T2 trans I had in my FB was taking names on GT1 class cars at my local track. So, just saying you don't need a $10k+ 20b build to win them over.

Now, in saying that, what you said holds true for the engines. I had $3k in my 13b keg alone and that was with pulling favours...

I'm definitely upping the ante . 3K minimum if I'm lucky... that's why I'm a dilusional newb. It's really hard to have the patience to save all I need. I'm looking at a 13B 6 Port FC series with the S4 Rotars

Do you own a race prepared car already and just need a powerplant or do you need to build the car as well?

I wouldn't advise starting in EProd; realistically speaking it's another dogbox class, the slicks aren't great to learn on, competitive power takes a lot of wringing out the engine and it takes some learning to have a reliable engine. If you're building from scratch, which it sounds like you are, it's going to be around $20k to have a competitive car. If you have experience with what works and what doesn't, fab your own stuff, have spare parts, jigs and bodywork molds you might be able to drop that to about half that (Tom Thrash, RIP, said he could replace his cars for less than that but he had a *lot* of experience and knew what was and wasn't necessary for him) but you could just as easily have more money into it. Then there's the consumables cost.

If you want to roadrace a 1st gen RX-7 with SCCA and don't have prior experience with rotaries or roadracing, run it in ITA or ITS. The suspension will be broadly similar to lower level EProd cars, but on more forgiving tires, and you won't have to try to figure out how to make an EProd style street port be reliable.

Well I surely don't have 20K to invest. I was hoping not to have to need a dogbox. Eprod class is not tube chassis is it? I was thinking more along the lines of peicing my car together for around 10k is what I hope.

EProd is unibody with widebody fenders and the like; it's basically the most modified non-tube frame SCCA roadrace class, and it's just a matter of all the prices for everything stacking up. Improved Touring could be well within that sort of budget without too much trouble though.

If your budget is $10k, buy an ITS (2nd Gen) or ITA (1st Gen). You aren't going to build a winner from scratch for $10k but can buy a mid-pack IT car for that price. As far as EP, $20k is what it would cost you if you had already spent $60k+ figuring out what to do and what not to do and did the work yourself. The costs are way more than you think, I wish someone had told me the truth before I got hooked.

Learn from us who have made the mistakes. You will have a lot more fun in a spec miata and it's realistically the only thing in your budget from what I am hearing. Even a PT/IT car to make competitive is either, a lot of in-house resources and 15k+ or more like 20-30k with limited in-house resources.

So many racers have told me point blank they wish they would have started in spec miata, because when they try it after doing all the other forms of club racing they have far more fun in a spec class than other classes.

I agree with both of these statements.

To give you an idea. We do all of our own labor and fabrication ( I have access to MIG, TIG, Plasma Cutter, Mill, Lathes etc). The only thing that we had to pay labor for was Balancing the Engine and Lengthening the Pinion Shaft. Other than that it was all on us and materials. We are into the car (NASA PTD) approx 13k.

The rolling chassis with bad engine was $300.
Few Hundred spent on other blown up cars for "Spares"

Things that we "Saved" on.
Roll cage was traded labor.
Wheels are used Mustang GT 15x7
Gauges we picked up used.
Suspension (double adjustable shocks, Spherical bearings, Speedway sway bar and torsen Diff) was purchased from an aborted EP project for pennies on the dollar.
Fire system, Accusump, Coilovers, Camber plates, Seat, and assorted other pieces were acquired from cars that we owned and parted out.
Tires are used Continental from a Grand Am Cup team
Paint was free from a sponsor

Hopefully you get the idea that we didn't buy the high end of everything as we have a budget to work within.

Besides getting the car track worthy, you need a Helmet, drivers suit, gloves, socks, shoes, Hans (over $1k in driver safety)

Also don't forget you need a Truck, Trailer, Storage

Thanks, I just got the truck and trailer , I have a garage. I can see you pieced a car together through many resources. I have been slowly piecing it together through the same sort of means. There are a few people around from whom I've gotten great deals . I'm trying to do as much work on my own as I'm capable of. I really want to get on the track soon, so I'm really gonna leave this project with a lot to be desired. I just want to get out there and have fun expressing my driving skill at whatever level I will be able to afford.

If you can get the engine here, I can definitely help out.