Build questions
 

I have a 1980 RX7 that is now my race car project. I have built 2 Hondas for racing, but i really don't know alot about rotaries yet. I am shooting for a high hp n/a class. Here are my questions:

Do i need to swap to a 13b?
What rotors would be best and where do i get them?
Ceramic or steel apex seals?
2mm or 3mm apex seals?

I think I can handle the rest. Thanks

13b will make more power, but you can get 200 rwhp from a race ported 12a.
Most are using stock rotors, having the entire rotating assembleys balanced. Racing beat sells lightend rotors. Others sell them as well. Ceramic seals will make the most power and last forever. Someone else will need to chime in on the size of the seals.

What do you consider high horsepower? In what class do you intend to compete? The answer dictate the direction you need to go.

The first question is what class / sanctioning body are you building the car for? Then build the car to those specific rules.

I can only speak for SCCA and ICSCC here in the NW, but many classes do not allow engine changes between differing models. Or if they do, then you have to change everything that was different between the models.

SCCA E-Production is what i am shooting for. From my research i need about 280 to be competitive.

Also what are some of your 1st gen suspension setups?

Check out Jim Susko at G Force Engineering. He is a retired GM suspension engineer and has a complete line up of 1st Gen parts.

Jim worked for Cooper Tire, not GM. (You still should call him for your suspension,though)

With the porting rules in EP I think you're a little high on your HP estimate. I think about 220 whp get you in the hunt.

what would a good balance and port job, ignition system, fuel system, lightened rotors and ceramic seals put a 13b at hp wise?

Jim is a great guy. Most of the front runners run his parts. RE Speed is making some nice stuff as well. Remember if you run the 13b there is a weight penalty of 140#.

I'm going to guess about what jgrewe said...220, maybe a little more with your max build motor. I've never heard of a 12a pulling more than 205 range. This assumes building to SCCA street port specs.

^ and there are venturi size limits for the carb, off hand I don't know what they are for a 12A FB but FC's are limited to 42mm. So no matter what you think you can get with great ports, you will still be limited by breathing through a straw. lol

do i have to use a 13b out of 79-85? that is what i thought the e-prod rules were stating? does anyone know?

You can only update and backdate on cars that are listed on the same page. IIRC you are correct, only the early 13B can go in the FB.

Nobody will care until you beat them but why take the chance. I'm pretty sure all the fast guys with FB's are running 12A's.(I stopped keeping track when I switched to FC's, its hard enough to keep up to date on one chassis)

Right, except for Bob Neil, you can see his car build pics on Mazdatrix.com. You must run the 6 port housings from 84-85 no others are allowed. There are a few others running the 13b but no one else has been in the front pack at the runoffs consistently except for Bob.

I did quite a bit of research and asking around a few years back and decided to go 12a. One of the reasons was that the lower rotating mass of the 12a lets you spin the motor faster and rebuild less often than the 13b. You can get the car lighter, and for you really fast guys the tires have a better change lasting the entire race. A lot of the mid pack guys go 2-3 seasons on a 12a motor. No doubt the 13b will have more power. As a matter of fact the current EP champ experimented with the 13b during the season and went back to the 12a for the runoffs and won. He blew up several 13b motors during the season, for whatever reason he could never get them right.

What transmission and gearing is best to use if I use the 12A?

Also, i need to replace my steering box. Is there a better box that i can replace it with or do i need to stick with the same one?

Have to keep stock steering box.

The best tranny would be a dog ring box purpose built for racing. Figure on $5,000 for one of those. Spreading your gears from about 2:1 to 1:1 is a good start, its all track dependent. Second best would be a 6sp miata gear set in your tranny case but you only use 5 gears. A few hundred for a donor box and some machine work and you're all set for less than $600 if you do it yourself.

best setup for the 12A? 1) Nikki Carb w/ primary choke bored to match secondary choke on a stock manifold or 2)Auto-type 2BBL w/ 38mm choke on a "dual y" manifold

Tough call on the carb. I would say the Weber 48 IDA w/ the 38 chokes. You can get a lot out of the Nikki though, it might take some dyno testing to get your answer. I would start with what ever you have available and then worry about the few HP difference later.

Pretty much everyone in EP with a 12a is running the Weber, as posted above. There is a guy in the first gen forum Carl PB&J racing that modifies the Nikki to flow enough to run in ep.

Weight reduction: even with the gutting and replacing all needed glass with lexan the car is probably not going to be down to its minimum weight. What is the most cost effective way of shedding some more pounds?

You can get them down to minimum weight no problem. Just look at the car and take off everything that doesn't make it go, stop, or turn.

If you keep the car simple you can get it below 2000 lbs easy. Cut off every unused bracket, door bars, remove headlight assemblies, brake booster, the list goes on.

Here is a couple of build pics. Dry ice works great to get the stuff off the floor. Still expect to use some solvents and scrape.......

where can someone get dry ice from? i hate that sound-proofing material.

I got it from a place called Airgas here locally. They supply to welding houses and the like. I've heard of grocery stores having it. I recall an entire thread in this section devoted to this issue. Search for dry ice and I'll bet you find it. The guy at the cage shop said mine was the cleanest car he'd seen that had not been dipped. I even got the stuff off the bottom of the car. I was going to seam weld it but there is so much seam sealer in these cars, that I figured it be fine. If I had a hook up I would have bead blasted it, but way to expensive. I was quoted over a grand.