Teach me about rotary swaps

aussiesmg wrote: porting is very subjective and depends a lot upon experience, a street or extend port is a moderate improvement on stock, monster port is a large street port, bridgeport becomes 2 ports as they cross the apex seal line leaving a bridge, a J port is radical and best left to those with a lot of experience as it really pushes the limits of the bridge. Bridgeports etc are rough running and not very street friendly. If you want to keep it for street use I recommend going to an extend port

No street use whatsoever.

Brett_Murphy wrote: If you take a 13B six port and wire the secondary ports open all the time, you get a really good high RPM engine that runs on pump gas and will last a long, long time.

Wha? I don't understand. explain "wire the secondary ports open" please?

The six port 13B has a set of vaccuum operated ports for better high-rpm breathing.

aussiesmg wrote:

tuna55 wrote: OK, how much power can they make with a iffy header and a tiny bit of carb work and porting? How much is the weight difference?

Depending upon the engines strength, stock 12a made 115 hp when new, with the mods I had it made around 150hp which was a nice street car but not world beating. A 4 port 13b with similar mods should be around 165hp, but they are getting hard to find. 13b 6 port should be similar but keep the fuel injection.

I presume this means that the six ports are FI only? So I am looking at 13B with 4 port or a 12A. Sounds interesting.

You can run the six port on carbs, but you need to wire open the additional ports IIRC .

That said, I'd look for a street ported 4-port 13B.

Tuna, You can have the '85 12a that I've got sitting in my parents barn if you promise to put it in your LeMons Volvo. It's 8 hrs away from you though.

cghstang wrote: Tuna, You can have the '85 12a that I've got sitting in my parents barn if you promise to put it in your LeMons Volvo. It's 8 hrs away from you though.

Can it wait? We are talking about resurrecting Charlie in a few years when my kids take less than 130% of my time. I'll totally take you up on it at that point, though. 'd even make the drive to pick it up probably

It's been waiting for a couple of years, probably not going anywhere too soon. I did get rid of the trans/header/driveshaft last year though.

aussiesmg wrote: Bridgeported RX4 http://www.youtube.com/watch?v=rKmK-paBLcE

Just for the record, I hate the way they sound, and that one was no exception. Oh well...

I am wondering...the 13b engines seem easier to come by. But they are FI. What's the easiest AND cheapest way to carb them? We're talking LeMons $$ here.

Racing Beat makes an intake for a Holly carb. For Lemons I wouldn't port it. You really need to talk to Jensenman / Curmudgeon. He has done several rotary swaps and just finished a 13B in a Jensen. Knowing him, he'll probably pop in this evening.

volvoclearinghouse wrote: I am wondering...the 13b engines seem easier to come by. But they are FI. What's the easiest AND cheapest way to carb them? We're talking LeMons $$ here.

Mike, I think they're just saying if you want to do that, just get a carb intake and slap it on. The distributor is the only hurdle if the FI means it has some sort of electronic ignition to boot.

Plus, we have a free 12A up there a few posts anyway...

Toyman01 wrote: For Lemons I wouldn't port it.

Why?

The spinning triangles are loud, like really really loud, does lemons have a dB rule, if so you've got to find a way to hush it up and EGTs are known to be really hot as well, putting a lot of stress on the exhaust system.

The fuel injected 13Bs up until the FDs used a dizzy gear for timing. It plugged right into the same kind of hole the distributors had on the 12As and 13B 4 ports and just sent the signal off to the ECU.

I don't think it would be very hard at all to get a regular distributor and just wedge it in there, but I've never really tried it, either.

Edit: Also, the 6 port vs 4 port question has been answered. There are a bunch of people in and around Raleigh, NC with rotary parts coming out of their noses. I can give you the contact information for some of them if you wind up needing parts.

Brett_Murphy wrote: I don't think it would be very hard *at all* to get a regular distributor and just wedge it in there, but I've never really tried it, either.

The distributor bolts in place of the FC CAS - or vice versa; on Greg's car we swapped a FC ignition into a distributor equipped motor.

The '84-'85 GSL-SE used a unique combination of EFI with two injectors and a distributor. FCs were all EFI as well (no mechanical injection that I'm aware of, but the ECU got a total redesign in '89) but had four injectors and distributorless ignition.

In reply to tuna55:

Because lemons is about making laps more than making speed. The Civic was bone stock and slow as hell and we still finished 10th. The t-bird was fast as hell and didn't finish. That and last I checked the seal/gasket kits were big money. Run it stock and keep it running.

I have an 84 or 85 GSL-SE in my backyard that had a 13b and a 5 speed in it. I yanked the engine for another project that never got going, I've still got the drivetrian...my main hurdle was trying to figure out how to carb the engine, as the EFI setup was a big effing wire harness of nightmares. I researched the racing beat intakes but they were too much $$. Now the engine seems to be seized. :-( So I'll probably end up doing my first ever rebuild job on a spinning triangles engine.

I take it a 12A intake won't bolt up at all to a 13B engine?

In reply to imirk: They say something like 92 dB at 50 feet or something, but also say a single cherry bomb muffler should be plenty. For a rotary, more may be needed.

Toyman01 wrote: In reply to tuna55: Because lemons is about making laps more than making speed. The Civic was bone stock and slow as hell and we still finished 10th. The t-bird was fast as hell and didn't finish. That and last I checked the seal/gasket kits were big money. Run it stock and keep it running.

See, I live in small block chevy land - I didn't realize that the seals and gaskets were big $$, I think you're right then. What gains are there to be had in 12A and 13B land by just doing intake and exhaust?

volvoclearinghouse wrote: In reply to imirk: They say something like 92 dB at 50 feet or something, but also say a single cherry bomb muffler should be plenty. For a rotary, more may be needed.

I suspect a real muffler as well as a resonator - rotaries sound TERRIBLE!

you dont like your cars to sound like chainsaws??

imirk wrote: you dont like your cars to sound like chainsaws??

Chainsaws sound awesome compared to rotaries. I wrote about the sound in a thread a while back. I heard a few at the strip and the sound is terrifying. The only thing I ever heard that was close to that terrible was a 5/8ths scale dragster powered by a snowmobile engine with an awful tuned pipe. That guy went to a lot of effort to run mid 10s.

tuna55 wrote:

Toyman01 wrote: In reply to tuna55: Because lemons is about making laps more than making speed. The Civic was bone stock and slow as hell and we still finished 10th. The t-bird was fast as hell and didn't finish. That and last I checked the seal/gasket kits were big money. Run it stock and keep it running.

See, I live in small block chevy land - I didn't realize that the seals and gaskets were big $$, I think you're right then. What gains are there to be had in 12A and 13B land by just doing intake and exhaust?

Intake and exhaust manifolds can make pretty big power gains over stock. Especially on a 12A. The 12A was 110hp stock. With headers and a good manifold you can push that over 140. Think of it like building a SBC to turn 7K and then putting stock cast manifolds on it. A rotary needs to breath. Racing Beat will also sell you the exhaust flange to build your own exhausts. Use good tube to the collector because the exhaust gets HOT. Ebay lists intakes fairly often, but even the stock intake and Nikki 4 barrel run decent if you don't have the room in the budget. Bypass all the smog crap and snatch the choke out of it. The biggest gains are in the exhaust. For 13B stuff you probably need to talk to Curmudgeon. I'm more of a carbed 12A guy.

A stock NA rotary is as reliable as dirt. Don't run it hot, don't run out of oil and keep it turned up. Most of them crap out from carbon. If it doesn't see the red line every time you run it, you're doing it wrong.