(INTAKE) Weird Nikki 6 port 13B manifold
01-29-08, 04:08 PM
#1
(INTAKE) Weird Nikki 6 port 13B manifold
Take a look at this abomination.
Did it work? It kinda sorta did on an RE-SI engine (like a J-spec GSL-SE but with smaller ports). The problem with the RE-SI is the intermediate ports are even smaller than a GSL-SE or S4 NA. So you have these monsterous channels at the top of the manifold, which squeeze down into normal FB runners, then which join into an aluminum plate that somebody cut for the 6 port 13B pattern, and since there are no aux port actuators, you must leave the sleeves out of the engine. No chance of using Pineapple sleeves or any of that. What you're left with is too much port timing at the end plates with poor flow, and not enough port timing at the intermediate plate with almost no flow. Couple that with US-spec early opening+early closing exhaust ports of the RE-SI (same as US-spec REPU, Cosmo, RX-4 and '81-'85 12As), choking off the engine, and you have one gutless wonder.
It was in my friend's REPU. It was pretty gutless so he got himself a Camden and I got this manifold and the Nikki that was on it. A '79-'80 style, but probably J-spec because it has a few feature sI've never seen before. Anyway the venturi boostrs are no longer glued to the main body and can be lifted up and removed from th ecarb. There is some wear from the metal to metal rubbing. Plus being an SA style carb, according to Sterling, is harder to dial in the air fuel mixture curve. It has a set of 106 Hitachi primary fuel jets, stock 160 secondaries, and 90 pri iar bleeds with 120 (yeah!) secondary bleeds. I'm going to try the carb on my nice trusty 12A to see if it's even worth fixing. If not, I'll harvest the good bits for an '81-'85 Nikki that needs some attention.
As for the weird 6 port manifold, I don't know yet. I'd appreciate your input.
Did it work? It kinda sorta did on an RE-SI engine (like a J-spec GSL-SE but with smaller ports). The problem with the RE-SI is the intermediate ports are even smaller than a GSL-SE or S4 NA. So you have these monsterous channels at the top of the manifold, which squeeze down into normal FB runners, then which join into an aluminum plate that somebody cut for the 6 port 13B pattern, and since there are no aux port actuators, you must leave the sleeves out of the engine. No chance of using Pineapple sleeves or any of that. What you're left with is too much port timing at the end plates with poor flow, and not enough port timing at the intermediate plate with almost no flow. Couple that with US-spec early opening+early closing exhaust ports of the RE-SI (same as US-spec REPU, Cosmo, RX-4 and '81-'85 12As), choking off the engine, and you have one gutless wonder.
It was in my friend's REPU. It was pretty gutless so he got himself a Camden and I got this manifold and the Nikki that was on it. A '79-'80 style, but probably J-spec because it has a few feature sI've never seen before. Anyway the venturi boostrs are no longer glued to the main body and can be lifted up and removed from th ecarb. There is some wear from the metal to metal rubbing. Plus being an SA style carb, according to Sterling, is harder to dial in the air fuel mixture curve. It has a set of 106 Hitachi primary fuel jets, stock 160 secondaries, and 90 pri iar bleeds with 120 (yeah!) secondary bleeds. I'm going to try the carb on my nice trusty 12A to see if it's even worth fixing. If not, I'll harvest the good bits for an '81-'85 Nikki that needs some attention.
As for the weird 6 port manifold, I don't know yet. I'd appreciate your input.
01-29-08, 04:13 PM
#2
Eats, Sleeps, Dreams Rotary
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Wasnt there a 6 port 12a? Not that savvy on the older (historic) rotary but I recall seeing a black and red stock air cleaner that had 6 port on it.
01-29-08, 04:36 PM
#3
Yeah, and my friend has one. Maybe this manifold came from one, or maybe it was a normal FB manifold. It looks like it because it had a shutter valve that somebody removed. I don't know that much about the 6 port 12As so I can't say for sure.
01-29-08, 04:48 PM
#4
I have one project car that needs a 13B. It is the GLC I've mentioned a few times recently. I was all set to build a 4 port 13B for it the other day and use a typical Hitachi carb and 4 port manifold. Even cleaned up the side plates and everything. I am, however, willing to entertain thoughts of an experiemental nature, namely figuring out a way to use this weird 6 port chymera. 
Some recent experiements with various Hitachis and a modded (by me) '84-'85 Nikki carb have convinced me the Nikki is a superior carb and does not suffer from the funky fuel curve problems of Hitachis and '79-'80 Nikkis. I was wholey impressed by the performance when switching from slightly larger than stock 94 primary jets and 90 primary air bleeds, to 100 jets and 70 air bleeds. It now has power up to 7k where before it would run out of breath up there, and the primary powerband seems to have gotten wider with more power down low. The carb used to only come alive when you'd open the secondaries above about 3800RPM. Now it has power pretty much everywhere and the transition has become smoother.
I was planning on cutting a set of Nikki stud holes in one of my Hitachi manifolds so I could take advantage of the Nikki's better power delivery when I realised upon test fitting a Nikki in my REPU the other day, that it won't fit under the hood. The Nikki is taller than a Hitachi, and the MOP lines and rod are about an inch too short. This is because the Hitachi manifold is about an inch taller than a Nikki manifold. Also the throttle cable was too long (at least that's how the weird carb was that came with the 6 port manifold; a normal Nikki might be different).
Since a Nikki on a Hitachi manifold won't work, I could either get a 12A to 13B manifold adaptor, or mod a Nikki manifold to fit. Or run without an air cleaner assembly. Still would need to mod the MOP lines and rod. Not sure about the throttle cable, but probably.
A better option would be to use a manifold that already has the right dimensions to allow the Nikki to sit lower. Since this 6 port mainfold is the only one like that, I'm considering it. It would need to be repaired, or course. I do still have the RE-SI end plates. I also have access to a '74 REPU intermediate plate with its short port runners and '74 spec port timing. That might work. It would provide much more flow than the RE-SI or a GSL-SE intermediate, and better match the non-sleeveable aux ports in port timing. Of course the low end torque would be pretty bad I'm thinking, but the GLC is a small light car. I bet I could get away with it.
Some recent experiements with various Hitachis and a modded (by me) '84-'85 Nikki carb have convinced me the Nikki is a superior carb and does not suffer from the funky fuel curve problems of Hitachis and '79-'80 Nikkis. I was wholey impressed by the performance when switching from slightly larger than stock 94 primary jets and 90 primary air bleeds, to 100 jets and 70 air bleeds. It now has power up to 7k where before it would run out of breath up there, and the primary powerband seems to have gotten wider with more power down low. The carb used to only come alive when you'd open the secondaries above about 3800RPM. Now it has power pretty much everywhere and the transition has become smoother.
I was planning on cutting a set of Nikki stud holes in one of my Hitachi manifolds so I could take advantage of the Nikki's better power delivery when I realised upon test fitting a Nikki in my REPU the other day, that it won't fit under the hood. The Nikki is taller than a Hitachi, and the MOP lines and rod are about an inch too short. This is because the Hitachi manifold is about an inch taller than a Nikki manifold. Also the throttle cable was too long (at least that's how the weird carb was that came with the 6 port manifold; a normal Nikki might be different).
Since a Nikki on a Hitachi manifold won't work, I could either get a 12A to 13B manifold adaptor, or mod a Nikki manifold to fit. Or run without an air cleaner assembly. Still would need to mod the MOP lines and rod. Not sure about the throttle cable, but probably.
A better option would be to use a manifold that already has the right dimensions to allow the Nikki to sit lower. Since this 6 port mainfold is the only one like that, I'm considering it. It would need to be repaired, or course. I do still have the RE-SI end plates. I also have access to a '74 REPU intermediate plate with its short port runners and '74 spec port timing.
That might work. It would provide much more flow than the RE-SI or a GSL-SE intermediate, and better match the non-sleeveable aux ports in port timing. Of course the low end torque would be pretty bad I'm thinking, but the GLC is a small light car. I bet I could get away with it.
01-29-08, 05:09 PM
#5
Sorry for all the reading.
What it comes down to is I want to use a Nikki because they are really great carbs. The only way to get one to fit in th eGLc is to use the 6 port manifold and build a 6 port engine. The downside is the manifold must be repared (I know a guy that can weld aluminum) and the low end driveability might suck *****. I want my dad to be able to drive the car when finished so I spent a lot of time researching flyweels and clutches so it will have easy pedal effort, but enough holding capacity for a 13B. (either the superlight steel 8 pound flywheel with a heavy pressure plate, or a Racing Beat light steel 13 pound flywheel with a light pressure plate)
I've built several 4 port 13Bs and I know they are great, but I feel in order to expand my knowledge base, I must venture into the 6 port realm. I'm running low on good hitachi carbs and manifolds these days, so I'm looking forward to experiementing with Nikkis and changing whatever needs to be modded to fit the different throttle cable, choke cable (for my dad) and other stuff.
I still have a trump card too; if the 6 port just doesn't work out, I can do a quickie rebuild and go with a 4 port.
So what do you guys think? 6 port? 4 port? The car already has a 4 port and it works pretty well with large street ports. The idle is a little lumpy and the carb is a little cold blooded. Also doesn't like to rev much because it's a Hitachi. My dad would not like it. If the 6 port turns out that way too, I'll do a non-ported 4 port.
If you like following my projects, you won't want to miss this.
What it comes down to is I want to use a Nikki because they are really great carbs. The only way to get one to fit in th eGLc is to use the 6 port manifold and build a 6 port engine. The downside is the manifold must be repared (I know a guy that can weld aluminum) and the low end driveability might suck *****. I want my dad to be able to drive the car when finished so I spent a lot of time researching flyweels and clutches so it will have easy pedal effort, but enough holding capacity for a 13B. (either the superlight steel 8 pound flywheel with a heavy pressure plate, or a Racing Beat light steel 13 pound flywheel with a light pressure plate)
I've built several 4 port 13Bs and I know they are great, but I feel in order to expand my knowledge base, I must venture into the 6 port realm. I'm running low on good hitachi carbs and manifolds these days, so I'm looking forward to experiementing with Nikkis and changing whatever needs to be modded to fit the different throttle cable, choke cable (for my dad) and other stuff.
I still have a trump card too; if the 6 port just doesn't work out, I can do a quickie rebuild and go with a 4 port.
So what do you guys think? 6 port? 4 port? The car already has a 4 port and it works pretty well with large street ports. The idle is a little lumpy and the carb is a little cold blooded. Also doesn't like to rev much because it's a Hitachi. My dad would not like it. If the 6 port turns out that way too, I'll do a non-ported 4 port.
If you like following my projects, you won't want to miss this.
01-29-08, 05:18 PM
#6
Wow, I must be inspired. Look at all the posts I've made in the last hour. That right there tells me it's worth exploring this 6 port Nikki thing further.
Here are the rotors I'd like to use.
One suffered broken apex seals in the RE-SI engine (right) as is the fate of all GSL-SE engines since they run so well for so long (one broke at 5.5mm). The other rotor came out of a water damaged nitrided R5 in my friend's garage. When he tried to get the side seals out, they were stuck and broke. He gave up and it sat on the floor for several years attracting bugs and debris. I was able to dig the side seals out in like 5 minutes using a special new tool I made out of an old box cutter blade.
Both are C weight, but just picking them up, the RE-SI feels a little lighter. They use the same counterweights and flywheels. Maybe I'm imagining it.
The Y side plates for the 4 port, should I decide to build it.
The 6 port RE-SI end plates are not pictured by maybe I can find a shot of the intermediate plate and its microscopic ports...
Here are the rotors I'd like to use.
One suffered broken apex seals in the RE-SI engine (right) as is the fate of all GSL-SE engines since they run so well for so long (one broke at 5.5mm). The other rotor came out of a water damaged nitrided R5 in my friend's garage. When he tried to get the side seals out, they were stuck and broke. He gave up and it sat on the floor for several years attracting bugs and debris. I was able to dig the side seals out in like 5 minutes using a special new tool I made out of an old box cutter blade.
Both are C weight, but just picking them up, the RE-SI feels a little lighter. They use the same counterweights and flywheels. Maybe I'm imagining it.The Y side plates for the 4 port, should I decide to build it.
The 6 port RE-SI end plates are not pictured by maybe I can find a shot of the intermediate plate and its microscopic ports...
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01-29-08, 05:34 PM
#9
Sorry to keep posting, but I found some 6 port 12A pictures.
EGR port.
Awesome cast iron header. Note the motor mount studs like a GSL-SE.
6 port manifold with a Nikki. Not sure how it flows yet, which runners etc.
'80 type dizzy. Short oil filter pedestal. Motor mount studs.
EGR port.
Awesome cast iron header. Note the motor mount studs like a GSL-SE.
6 port manifold with a Nikki. Not sure how it flows yet, which runners etc.
'80 type dizzy. Short oil filter pedestal. Motor mount studs.
01-29-08, 05:54 PM
#10
I think I just figured it out. The reason the carb seems to share features of an SA (main body, thottle body) and FB (top cover) and why it has 120 secondary air bleeds vs 140 on all the 4 port 12A carbs I've ever seen, is because the manifold and carb indeed are from a 6 port 12A. The 120 air bleeds keep the fuel meetering into the carb up to a slightly higher RPM and/or slightly greater CFM than a typical 4 port 12A would see.
There is a big difference in port timing though. The 6 port 12A has very late opening intake ports, with closing being about the same as a GSL-SE. The secondaries are also smaller than the RE-SI pictured above. The aux ports are um.. I can't remember what shape or timing they had. It's been a while since I saw a set of 6 port 12A plates.
Thanks to this thread, and the experiments I've done on my nice (4 port) 12A with a set of '74 spec ports I cut with my dremel, I now believe I can 'get away' with a '74 intermediate plate and the RE-SI end plates with their current port timing. The primaries will flow a little more since the engine is a 13B, and the secondaries will flow a lot more due to the timing of the aux ports.
The primary carb barrels should be able to flow well enough fuel with let's say 106 primary jets (as mentioned above) and perhaps some 70 or maybe even 60 primary air bleeds (they're worth their weight in gold!) and the 120 secondary air bleeds from the 6 port 12A carb (mentioned above, and worth their weight in uh silver, or something lol). I have a set of 170 and 190 secondary jets if I need to use them, but Sterling says the stock 160s are plenty big enough in his Sterling carbs with various levels of porting. Only experiements will bear this out on this engine, of course.
Wow, it's a real 6 port manifold and carb that somebody butchured to make it fit a 13B. Wow.
The 120 air bleeds keep the fuel meetering into the carb up to a slightly higher RPM and/or slightly greater CFM than a typical 4 port 12A would see.There is a big difference in port timing though. The 6 port 12A has very late opening intake ports, with closing being about the same as a GSL-SE. The secondaries are also smaller than the RE-SI pictured above. The aux ports are um.. I can't remember what shape or timing they had. It's been a while since I saw a set of 6 port 12A plates.
Thanks to this thread, and the experiments I've done on my nice (4 port) 12A with a set of '74 spec ports I cut with my dremel, I now believe I can 'get away' with a '74 intermediate plate and the RE-SI end plates with their current port timing. The primaries will flow a little more since the engine is a 13B, and the secondaries will flow a lot more due to the timing of the aux ports.
The primary carb barrels should be able to flow well enough fuel with let's say 106 primary jets (as mentioned above) and perhaps some 70 or maybe even 60 primary air bleeds (they're worth their weight in gold!) and the 120 secondary air bleeds from the 6 port 12A carb (mentioned above, and worth their weight in uh silver, or something lol). I have a set of 170 and 190 secondary jets if I need to use them, but Sterling says the stock 160s are plenty big enough in his Sterling carbs with various levels of porting. Only experiements will bear this out on this engine, of course.
Wow, it's a real 6 port manifold and carb that somebody butchured to make it fit a 13B. Wow.
