I have 12A i'm fitting into my Viva.Its a hybrid of UK spec rx2 housings and series 2 rx7 plates with standard ports. It did have a elford turbo hung on the side but that wont fit into Viva so for now I will carb it.

So i'm looking for a nikki with the right jets etc and I'm not that knowledgeable about what the differnces are between the various nikkis. I'd like one off a series 2 rx7 so it suits the standard ports without having to worry about jets- but will a series 1 nikki be fine. Didn't the series 1 rx7 only have 105 bhp? Was that due to the carb etc or were the ports smaller?

My series 2 rx7 12A I had in the chevette was bang on 115bhp when we dyno'd it.

Are the carbs on the first gens all the same but for jet sizes - i'm guessing you guys depending on which state your in would have carbs covered with all sorts of emmisions stuff)

any info would be great.

cheers all.

alex
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Some early s1 nikkis have a different shaped inlet (air horn). And the jets do vary slightly over the rx7 models. I wouldn't really worry about it tho.

 

The factory carb manual (downloadable from links in the FAQ) has complete details in the different jetting over the years. Probably your best raw-data source.

 

Primary jets range in these sizes:90, 91, 92, 93. All pretty small but match air bleeds and match stock ports depending on series; some had thermal reactors and later cars had a manifold. Thermal reactor carbs tended to be jetted richer for idle circuit and primary circuit. Secondaries were all 160.

 

OK-cheers for info . So I take it that the main carb body is the same throughout? I notice that the fuel lines can look different between carbs. any other main structural differences?

 

The body varies slightly with emissions gear. If we are only talking rx7 nikkis (the early RX2 nikkis are quite different again), some have a richer solenoid which richens the mixture at idle under certain conditions. Also some have a power valve (don't confuse this with conventional power valves, this one is electronic and used for emissions) on the base throttle body section.

And yes the fuel lines vary - later models have external fuel lines whereas earlier models have them inside the air horn. These early models also have components for the power valve circuit, in the air horn and the jet devices in the main body. And they also have two float bowl vents sticking straight out into the air path of the secondary barrels.

I'm curious as to why you want to know this though...? The effect of these differences is next to nothing..

 

the air vent solenoid valve was different between 79-82 and 83-85..

 

that's what i want to know- what the differences are between them and if they do change things or not- better or worse.
Now i know and i can sleep easy....cheers.
and now to get busy buying one!

 

OK. More carb questions. I just bought this one...




I got it cheap and its all there apart from a missing throttle cable mount which i'll just fabricate- i have one to copy.

Its meant to be off a series one rx7 but in comparing it to the pictures in my haynes manual for the rx7 it looks different to those shown. It looks just like a rx2 carb only it has all the same emmisions stuff that the series one carbs have. And I think RX2 carbs are made by zenith stromberg where as this one I have bought has nikki cast on its sides.

The rx2 supposedly has 130bhp and the rx7 series one has only 105bhp. How where they different- I know the rx2 had the exhaust ports with 3 holes- which looks even more restrictive...! was it down to the jetting and port sizes or was it the more restrictive emmisions stuff on the rx7 that stumped the power?

anyway- can I rejet this to suit a series 2 12A or should I just chuck it on and go from there.
I will of course remove all the emmisions crap as I always have done in the past.

 

About halfway down this page http://www.sterlingmetalworks.com/th...carburetor.htm there's a chart of all the North American 1st gen RX-7 Nikki carb factory jets. I don't know if the EU models were different.

 

Cheers - i'll have a look. I'll plonk the carb in place and see how it goes first.

Still curious as to why/how the rx2 had more power than the 7 and what made the differences?

 

The slight variations in jetting won't account for much. If you want to get more power out of the nikki, modify it. Looking for the best model of stock carby is a waste of time.

 

there are a bunch of differences between the US cars and the JDM/NZDM.

the 130hp cars are all rated @JIS, which is slightly higher than SAE net hp.

two the JDM/NZ/AUS rx2/3 up to i think 74 were emissions equipment free. they came with a cast iron "header" as standard.

the US spec engines all had thermal reactors (the REAPS system), and were rated at about 100hp SAE

 

cheers for that info fellas.
I'm not looking for more power but I just want to know i'll get at least 115bhp that my series two engine would have had. At a later date I'd really like to get a sterling carb when money isn't such an issue...

I have stripped the carb down and its all good with nice clear jets so once engine is bolted in place it'll go on and i'll see how it runs.

 

ive seen bigger dyno sheets out of stock carb/stock exhaust manifold engines, if you have a header 125 should be possible

 

OK... you won't lose any power using an older version of the Nikki.