On the way back from last weekends lemons race the team was thinking of ways to spice up the horsepower for the RX-7 The car has a carbureted 12A in it. After doing a little bit or research I found templates for DIY porting are rather inexpensive and can lead to huge power gains.
I have done a brief search over at RX7club but I have found the single to noise ratio there a bit unfavorable.
Has anyone here:
1) Actually used one of the several Porting templates out there?
2) What kind of seals and or gaskets must be replaced in the process (keep in mind this is a lemons car and we will have very little $$$ to work with)
3) Are there any unintended consequences we should be aware of (ie new carb required to meet new flow rates etc)
You'll certainly need to replace the gaskets between the irons and the chambers and possibly a few O-rings.
I'd expect you'd have to re-jet the carb to allow for the increased air flow unless you want to run very lean.
No firsthand experience, but you might try here: http://www.nopistons.com/forums/forum/81-rotary-engine-building-and-porting/
Probably not as active as RX7club, but that might be a good thing. There are some very knowledgeable folks on nopistons, as well as knuckleheads like myself.
You will likely need a full engine rebuild gasket kit. If you take part the long block/aka irons you have to replace the seals. I'm not sure if its economical to just get the main coolant seals, or buy the whole kit and sell it. I'm sure some RTV/reused gaskets can be used on the out side but the main coolant seals/o rings have to be done.
Its kinda like a rotary headgasket, only more critical. It'll also make the engine more reliable since any bad coolant or overheating will eat up those seals.
If you want real advice I can give you my bosses number and he can help you out. He has some NA 13B HP records (his 20B is up to 423WHP NA) so he might be able to help you with making some power.
You can always port it and upgrade the intakemanifold/carb later. It wont hurt any thing and it'll be more reliable.
~Alex
Alex , you are cutting right to the heart of my concerns, I also worry about apex seals, I think a new set of those would bust what little budget we have... couple in the cost of template and of a complete gasket kit and we would be deep in the penalty lap zone...
but if I don't have to replace the apex seals, and I could get away with just buying the coolant seals and do a okie RTV gasket job on the rest.... 
you can PM me your bosses number though I am not sure if I am quite ready for "high caliber advice" yet, I am just doing a little pre planning.
Edit nerdgasm* I am now officially a dork! woo hoo!
I'd PM you but this site is made my lazy gear heads and hardly any ones profile works :P
So just call 614 five nine two 7nine 9 one and talk to Logan. Thats the shop phone so give ita call 10am-7pm.
I know the side rotor seals are actually fine to reuse, just maybe the springs behind them need replaced, only if the engine burns oil. The apex seals, if the compression is good, you should be good. Its alot of if it works, dont fix it.
~Alex
Get a hold of 'Knurled' if you can. He has built many budget rotaries with various port configurations. The 13b he had at the beginning of this year was particularly nice (very flat usable torque curve) and is what I would want if I ever got another wankel-mobile.
Would a porting template count in the vehicle budget? It is not like it will be installed in the car. Wouldn't you treat it like any other tool purchase?
Big gains can be had in a rotary with just a free-flow exhaust, even with the stock ports. Look at the Racing Beat technical info section here.
Lance Hardshaft wrote:
Would a porting template count in the vehicle budget? It is not like it will be installed in the car. Wouldn't you treat it like any other tool purchase?
It's not the template or the porting, it's the cost of the seals. I was under the impression a seal kit is something ridiculous, like $700.
rotard wrote:
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BRAAAP... bamb!
BRAAAAP, BRAAAAAAP, BRAAAAAAAAP, bamb, BAMB!
Lance Hardshaft wrote:
Would a porting template count in the vehicle budget? It is not like it will be installed in the car. Wouldn't you treat it like any other tool purchase?
good point! though as another poster mentioned I am a bit concerned about the cost of the seal kit, though from what I have seen so far I think I ought to be able to re-use the apex seal (assuming they are in good condition)
cghstang wrote:
Get a hold of 'Knurled' if you can. He has built many budget rotaries with various port configurations. The 13b he had at the beginning of this year was particularly nice (very flat usable torque curve) and is what I would want if I ever got another wankel-mobile.
Paging Knurled!!! are you out there ?
You might try the private message function to get a hold of him. I'll see what I can dig up from rx7club that he's posted regarding that particular setup.
Edit: This is the best info I can find from rx7club on that particular engine- 13b half bridge. He's peejay on there.
I had a 12A in my much lamented and missed '79 RX7, if you slap shifted it to second hard it would go sideways and I was running 205/50-13 V710's.
If you go the porting route, you will definitely need the housing O rings (they will rip apart as the housings are separated) and the oil control ring O rings. Between those, you will probably spend $125-$150. That's before you touch a single hard part like apex seals. If the motor runs smoothly and evenly and doesn't overheat, I think I'd not want to crack into it.
A carbed 12A can be woken up nicely with a big ol' carburetor and opened exhaust. I hope you are running headers, if not I'd do that before any porting work. They pop up cheap on rx7club all the time. Mufflers are 'free' in LeMons, use a Walker DynoMax. Best compromise between noise and flow I have found so far.
Try finding a 390CFM Holley, they can be had cheap and an adapter plate to put it on the 12A manifold is easy to make. Even a big 2 barrel off a big block Ford can be a help, but you'll lose some driveability off the bottom and the adapter is harder to make.
The ignition timing can be bumped up for a hard to believe HP increase, you want to run the engine at ~4000 RPM and set the ignition timing at 22 degrees advance. Use a good quality dial advance timing light to do this! Much more than 22 degrees and ugly things happen under load.
Stock 12A's were rated at 100 HP. With the things I mention, you should have somewhere around 135 HP. That's not a lot for a, say, 2200 pound car. So if you are running a 1st gen body, start whacking off weight big time if you haven't already. Lose all the glass gut the doors etc. It shoudn't be real hard to get the car down around 1700 pounds.
You might also look for a Fiat 124 Spider that's in rough shape. 12A's are easy swaps. 
I stuffed a 12A in to a ford currier (mazda) pick up that came with 4:30 gears the rx7 had 390's wow the 430 made that motor seem like a v8.
Made a header from a big tube pacesetter cuting and welding as needed. I to went holley carb but over did it with 600cfm but it was on the shelf...
Lost an apex seal and never could get a title for the truck so i scraped it. 
thanks for the advice ~120 for soft seals... I hope we can support that with out residual value. The traqmate was indicating we were making ~100 hp at the wheels. Its got the stock carb and exhaust headers. Adjusting the timing is on our to do list. I don't have a comprehensive build thread posted up yet but between this thread:
http://grassrootsmotorsports.com/forum/grm/wish-me-luck/29273/page1/
and my soon to be updated garage entry:
http://grassrootsmotorsports.com/reader-rides/4646/
you can kinda see what has already been done.
We are looking at removing the rear hatch, that sucker is heavy! though I would like to replace it with some plastic or something, to keep the exhaust fumes out...
RX-Camino conversion? I've seen FCs get the pickup truck treatment. It will fit in with you Coors theme.
Heh. You are getting PLENTY of fumes from the cars in front of you, I'd not worry about fumes coming through the rear hatch. 
Run the exhaust out the passenger side in front of the wheel, put the muffler in that big floorpan bump where the converter used to go. Be forewarned: the fiberglass will burn out pretty quick and it smells weird as hell. If you leave plastic or whatever in the hatch opening, it creates a lot of drag. I'd lose the side glasses too, if you haven't already.
Go over the whole car: gut the underside of the hood and use pins to hold it down, gut the passenger door completely, gut the drivers' door but leave the factory door bar, scrape out the sound deadener, yank the dash completely if you haven't already, things like that. As a matter of fact, that lightening project's on the agenda for our Civic LeMons car.
About cutting the roof: before you do that, the latest Email I got said that cut down cars might not make it through tech.
Yea we have been through an event already. These mods are for the next event, we were foolish enough to purchase an old lemons racer so it has already been pretty thoroughly gutted. hood pinned etc. I am not anxious to reroute the exhaust as the PO seems to have done a pretty competent job at it...
I am not too worried about the areo, its clear we are down on power as we were being passed by all kinds of heavier cars with giant bits of weird prop material welded to their roof.
A header will help out a lot. It really is a huge bolt on difference. Tune the carb and set the advance and you will likely see a 20% increase. Strip it for weight and run the next race. If you need more power after that then think about porting.
I think I picked up my last Racing Beat Road Race header with a collector for $100.
You would have to do these supporting mods if you port it anyway. I would also be worried that if you open it you may not like the condition or you may not get it back together properly. Maybe try it on a spare motor first?
Good posts already, but I would add a couple of things:
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You can make the stock carb flow much better for little cost. Search "sterling carb" on rx7club. Two easiest things would be removing one of the "venturi arms" in each barrel and drilling out the existing jets by hand.
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I would do a ghetto compression test, and if it's passable leave it alone. If you do go inside the motor, I have a box of old used apex seals and side seals. I think some would measure "in spec" if you need some.
this thread has not helped to dissuade me from wanting to locate an old Mazda rotary engine and start working it over in an attempt to extract some more power from it, and then keep it around until I decide what to stuff it into/have the money to actually do it (SA22C-based tarmac rally car? ditch the factory 1.8 and make a RoMiata? I don't know)
What blows my mind is the hp gains people are claiming when they port the engine...
50% - 100% more power???
sure just grind off these little bits right here...
yes yes I know thats a vast oversimplification, but still...
Didn't grm make a good bit more porting their 13b in the ro-spit? If I recall, the best n/a those got was 148hp at the crank, and I think grm ported theirs, changed to a carb, and got 225 at the wheels (am I wrong here?). If so, that's at least a ((225-148)/148= 50%) 50% gain.
