lnbrown5981

i just got a 85 gs yesterday, and i am eager to start modifying it. it is a beautiful car, 0 dings, white, and the body has only one penny sized rust spot on the lower passenger rear panel. i am new to carbs. and 1st gens, but not rx7's. right now i am debating a 13bt or 13b-re into my 2nd gen n/a, which leaves me to another decision. should i do a rebuild with jumbo streetport on my 2 gen engine (which has 5/6 ports removed, emissions removed, alluminum flywheel, act clutch),and convert to carb and drop it into the 85? or should i forget about my 2 gen engine and drop a 12a turbo in there? which would be the best route to go for a good ? is the 12a just a drop in replacement? i know custom mounts would be required for the 13b engine, but as i have all the other neccesary parts from my 2nd gen i'd be willing to go either way.


thanks

lamar

vipernicus42

iTrader: (4)

12a turbo would be drop-in, but 12a turbos are either horrendously expensive (j-spec) or a pain in the *** to build. If you take a regular 12a, rebuild it and put a blow-through turbo, you're gonna be looking at a good amount of custom work... Moremazda did one, it's in the archive here:
https://www.rx7club.com/forum/showth...ight=12a+turbo

Just to give you an idea of what you'd be dealing with turbo'ing a 12a. If you can get a j-spec one, or an already built one though, it would defintely be the easiest swap.

Both the 12a turbo and the 13b street port make alot of power, I'm sure you'd be happy with either of them. So let money, availability, and the effort involved determine what you do.

Since you already have the 13b, dropping it in wouldn't be *too* bad.. The wiring on the ECU is a nightmare, but once you're done that it's worth having fuel injection. You can convert it to carb, but you'd wanna buy an aftermarket carb like a weber or holley. Racing Beat has some great aftermarket carbs that work wonders on rotaries. www.racingbeat.com . I'd just stick with Fuel Injection, and spend the week re-wiring it.

To do the swap you need:
A better fuel pump
A 13b exhaust header
Custom Mount Bracket (can be bought from RB)
GSL-SE front cover and oil pan too I think.

and some other stuff I can't remember, check the "TII into GSL-SE Swap" thread, it has a lot of great info, even for a GS, and it's stickied right at the top of the section.

Basically, the cheapest way to go is with the engine you already have. It may even be the easiest. The 13b sure can make some mad power, and the swap isn't *that* scary. Just do a search in this section and in the archives, you'll come up with LOADS of info on 13b swaps. You could probably also find some 12a turbo info, which would help you make the decision.

All said and done, my call:
13b from your second gen

lnbrown5981

just based on your info i would only need to get the 13b engine rebuilt w/street port, and the mounts and be ready to go. i already have a 13b header and presilencer on my 2nd gen, and if i stay e.f.i. i wont have to buy a carb set up. time will tell if i stay with the e.f.i setup, because i always wanted to learn more about carbs. i am now leaning more toward the 13b swap but i just had to hear from someone more experienced to be sure which way would work out better.

thanks again vipernicus42

johnrocks

13B only cuz I have one.



Peace-

FB II

12a turbo kneegrow! not the jspec, build your own. its just so much more fun to say you beat someone with one of mazda's smallest motors that was never turbo'd here in the states. WOO WOOOOOOOO!

Sk8r_dude

put a 13B in it, plenty of power, and naturally aspirated reliability.

nlc1179

go with the 13b, but use a 4port.