Got an engine I am going to rebuild. Going to open it up, clean it and Port it. Which would make for a more fun Rx7 to drive? !/2 Bridge or Large Street?

 

Full bridge! Don't waste your time with a half bridge.

 

lol beat me to it

 

let me explain it this way. 1/2 bridge port on a non turbo is like, all the drawbacks of the bridge (the idle, poor cuising etc) with none of the benifits of a bridge power wise.

it might have some benifit on a turbo, but looking at posted dyno sheets, its debateable

 

Tryng to stayaway from the full bridge, so i'm guessing the street maybe large should be the way to go. I'm not tryng to go turbo eighter.

What would I be looking at on a bridge port hp wise? I may not want to go full but I will have an other engine just incase it does'nt work for me.

 

I have a appx. 70ATDC street port 13B right now.

I am not terribly pleased with the way it drives. In a nutshell, you cannot drive on the primary throttle (EFI triple throttle assembly). It runs awful. You have to open the secondaries for it to run smoothly, and in fact I actually cranked up the secondary stop screw to make it more drivable, but it still doesn't like driving at 60mph in 5th, not enough load on the engine and it spits and stumbles. 80mph is just fine though

My P-port drove better. My P-port made less power, though.

I am hoping that the problem is just that the primary throttle is too small for the gonzo primary port hugeness and there's some weird reversion effects going on because of the super late closing. The fix will probably involve a single plate throttle body.

My 12A street port closed a hair past 60 ATDC, but I was using a 4 barrel carb, and it had drivability like stock. Better than stock, really, because it made enough midrange power that you didn't need to downshift on the highway for hills. So, this has me thinking it's a throttle body problem.

 

if you have a 6 port engine, bridge porting it is a waste of irons, its already open too late, making it open later, just hurts things.

on a 4 port, the power of the bridge depends a lot on the size and timing of the bridge, plus the exhaust behind it. the bigger the bridge, the more the exhaust matters.

 

So j9fd3s are you suggesting a street port?

 

it'll work better, especially if you have a 6 port motor.

 

Ive run into this same predicament as well with my 4 port 13b project. This thread helps.

 

I should point out that I'm glad I didn't go bridge with this one... or go extreme early opening like I'd been planning.

You *need* a free flowing exhaust with a high overlap engine. Period. I'm falling into Murtaugh syndrome (getting too old for this ****) and the only real use I have for my car is long distance driving. 3000rpm @ 20% throttle opening for three-four hours is exactly what bridge/peripheral engines do not like to do.

 

Do you got to change the ecu or upgrade with a Streetport large or mild?

 

Optimally... the stock ECU seems to have a brainlock on pulsewidths over something really low like 70%.

I don't know, I have never owned a factory fuel injected (rotary) car. Just carbureted and standalone.

 

I'll go with the Large Street port. I'll get the pineapples streetport template's. Should I do an exhuast port also, does do much for the n/a.

 

I'm looking at the 6th port sleeves PineappleRacing say's they will add 8hp, every lil bit helps. Has anybody tried them or heard of somebody thats has triedm?

 

I don't think opening up the exhaust ports on a streetport 13B will help much. Makes more differance on a 12A. I decided to go half-bridge on the last 12A I built. Kinda wish that I hadn't. True, you get the brap idle, but under 3 grand it's useless. You really don't get to the power band till 5 grand. Still breaking the engine in and I haven't turned it past 7 yet, but I kinda wish I would have stayed with a complete streetport. We'll see how she runs when I get to fully open it up.

 

Yeah, they kinda of have a problem with coming loose, hammering back and forth, and breaking the pin out of the sleeve, which gets ingested with the expected results.

 

My car isn't streetported, But I zip tied the 5th and 6th ports open, and I get 0 power until 5k. I think a Geo could take me until 5k, it's pretty bad...

 

Let me write this down: Do NOT ziptie 5th and 6th ports!!!

 

I just aquired a set of old style 4 port side plates (Y and R5). The intermediate is streetported. The front and rear are not. Should I do a half bridgeport?

Rotating assembly '86-'88 NA
2mm apex seals
GSL-SE rotor housings
Edelbrock 600 Performer series carb
REPU intake manifold (the high flowing one) with a carb adaptor or I could get an RB

Free flowing exhaust is planned. Camden 5" SC is kicking around. Or I could go turbo.

Should I do a half bridgeport? I've never done one before. I'm curious.

 

most cars do this. they need to have the pulsewidth to do full power at full cold enrichement and not fry the injectors

 

as mentioned the old school guys tried the 1/2 bridge in the 70's and it doesnt work, you get the BP idle and cruise, but the bridge isnt big enough to make any more power than a street port.

could it work? yes, boost will help, efi would help...

 

Hahahaha!!!! I can attest to that, as my last rebuild did that after about 20,000 miles!! It eventually came loose and shot back towards the pin, and then the pin got sucked in and put several dents in the rotor and even punctured it in one spot, as well as breaking the front iron and gouging the rotor housing. This is why my current setup is a 4-port.

 

j9fd3s: as mentioned the old school guys tried the 1/2 bridge in the 70's and it doesnt work, you get the BP idle and cruise, but the bridge isnt big enough to make any more power than a street port.

could it work? yes, boost will help, efi would help...

Thanks. Sounds like the half BP is out. I still have a few other options then.

Option B:
I have a set of heavily streetported Y plates. The only problem is the owner skitched a little across the rear plate in the oil seal track. This could possibly allow some oil to get sucked in under vacuum (it would be secondary only, which might not smoke at idle). If The engine is boosted it could allow a minute leak there into the crankcase. I could get a picture if you want to see the extent. At the very worst I could replace the plate and port it all the way out, although it's kind of time consuming to do it with a Dremel.

Option C:
I could do a peripheral port. I've never done any of those before. My friend is setting up a rig so he can do some p-ports for his 4 rotor project. I figure I can get in on some of that action. I'd use the unported R5 and Y end plates mentioned earlier and substitue the ported intermediate for a smaller NO sized plate.

Option D:
I could forget the big boy ports and try out a non ported low RPM torque monster. It would use a set of unported '74-'75 rotor housings, the end plates mentioned above as well as the small NO sized intermediate ports and a matching intake and carb. This would make a great engine for a baja.

As for intake options, I have access to a Camden 5" and maybe a Camden 7". The 7" belongs to the guy who skitched the rear street ported plate, so I could probably build a big streetport for him to use with his SC. It's just an option.

As for the P-port, I wonder how a DCOE would handle a set of small streetable p-ports? We're talking 12A sized on a 13B. I'd like to keep the stock 2mm apex seals so I'd limit RPM to 8k.

 

the racing beet solt lake car ran a 55 DCOE

http://www.22cworks.com/racingbeat.html