(INTAKE) Nikki and mani
 

Sounds like an old married couple from Del Boca Vista.

that is super clean

Nikki is an '84 model.

primary jets upped to 95
accelerator pump shot increased with:

drilled jet in banjo bolt
two gaskets on either side of AP diaphram
increased duration from a longer AP lever

removed most emissions.
removed emergency return spring (they seem to cause more problems than they prevent

simplified choke
added a spring because it seemed to work on another Nikki I modded a couple years ago

Decided to keep the altitude compensator this time.


The manifold received a second channel, an ACV blockoff plate, and the flapper valve was removed.


How do you guys think it will perform on a stock ported 12A with automatic tranny? I'm going to install it along with a header exhaust tomorrow. I bet it will make a noticeable improvement.

Thankyou. That's the hidden beauty in an oily crud covered part; it is usually perfectly preserved, as can be seen above. You just need to spend some time cleaning with a liquidy solvent that won't harm cadmium plating or any other surface.

I'd like to thank Sterling for this thread on Nikki mods https://www.rx7club.com/showthread.p...threadid=62678

And Rx7carl for his advice on manifolds and flow

I hope this old couple, who were married about 23 years ago, will find greater happiness with a second marriage. May they have many more years of fun together.

Jeff, by "channel" do you mean cutting grooves in the intake runners of the manifold to improve the velocity of the air fuel mixture? I have seen some other threads on here and it appears that it works really well. I'm curious to know your thoughts on this technique. I'm considering doing it on my 83 GS...

EDIT: I'd also like to know where you cut the grooves at in your intake, and why you chose the location. I'm very interested in this topic after running across it a couple of days ago...

I think he means that he opened a channel between the primary and secondary intakes at the top of the manifold. I've seen this done on Sterling intakes I think.

If you've taken off a Nikki from an FB manifold, and lifted the carb spacer out of the way, you'll see a flapper valve in one primary runner and nothing in the other. The other runner has a channel connecting the primary runner to the secondary runner. Older manifolds like the '79-'80 had channels in both sides and no flapper valve.

I removed the flapper valve from the FB mani above and cut a channel to match the other side like the '79 manifolds. From the research and experiments I've done on earlier seperate runner manifolds from REPUs and stuff, they showed an improvement in idle quality. Probably from secondaries and primaries both sucking on the idle circuit. I also think there was an increase in power too but the jury is still out on whether it improves high end at the expense of some low end. For example rotarygod thinks high end is improved but low end is hurt slightly. I think Rx7Carl agrees. Only dyno testing where only the manifold is swapped would be thebest answer to this question.

So to answer your question, I didn't cut grooves in it. I only tried to mimic what was in the other side using a drill, a chisel and a dremel too. :D

And you are hoping that doing this will smooth out the idle? Although you didn't cut grooves in the intake mani, what are your opinions of this tactic to improve the idle quality as well?

Cutting grooves might improve idle further due to the corrugated surface effect (sorry, I don't know the technical term) but I'm not at the point where I'm in need of it. I'm sure someone out there will try this.

As for the channel, it is an improvement over simply removing the flapper valve.

Man those FB manifold runners look fugly compared to the RX-3s.

Making the runners look the same going to each rotor seems like a good idea. A manifold that looks symetrical will probably have symetrical flow and more even EGT numbers.

You'd think. :D The truth is one primary still outflows the other. Still far better than the alternative of a totally stock manifold.

Jeff,

I'm interested to know how you cut your channel in there using only a chisel, a drill and a dremel? You got some very nice results there for just basic tools. I was figuring that you used an endmill to remove the material for the channel. How did you keep your cut so nice and square as you went down into the material? Also, how did you square up the bottom of the channel so well?

Again, nice work. Nikki and mani look fantastic together. :D

Jamie

Flattery will get you somewhere I suppose. :D

First I measured the depth of the stock channel with a drill bit. Then I applied masking tape so I'd know how deep to drill (turned out to be 15mm). I drew some lines on the manifold for where to cut. I made about three dimples in a row next to the lines for some pilot holes with about a 3/16" drill bit. While drilling, they walk a little but the end result was good enough for the final clean up step. The bit was stout enough I was able to kind of machine the aluminum by drilling in at angles after the initial holes were there, then slowly change the angle until it was straight up. It worked pretty well. Then I was left with a chunk in the middle so I hit it with a 1/2" bit which walked out as soon as it hit the support hole for the flapper valve shaft. Undaunted I drilled through the back side of the casting lump with the 3/16" and when enough material was removed, I hit it a couple times with a chisel and popped it out. The rest was brought down to nearly flat with the chisel. The final flattening and smoothing was done with the dremel and a cutting disc.

I'm familier with the tools described above and completed the channel very quickly but if this is your first time attempting anything like this, go slow, look for alternatives to my methods, do what makes sense to you etc.

For some light reading on the subject, check out peejay's manifold mod page. Read down to the end. He seems to think 'passages' (channels as I like to call them) are a necessity on a stock manifold with Nikki. http://www.geocities.com/izzmus/openspacer.html

I should say so! It looks like he was able to shave almost a second off of his quarter mile times just by doing this alone? Crazy stuff! Guess what I'm going to be doing to my manifold soon? :D

Too bad you're too far away. Otherwise, I will line up my son's stock 12-A motor loaded with IDA and dual exhaust; not too extreme of course since he is a new driver.

Yeah, channels really work!

Don't forget the hole on the outside of the primary runner (not seen in the picture above). I cut some NPT threads and cranked in a hex head plug. No vaccum leaks here. :)

One other question for you Jeff. Are you still using one of the black phenolic carb spacer with this setup? I'm curious because when I put together my setup like this, I will likely be using the black phenolic carb spacer still. I didn't know if it would be best to leave the spacer stock, cut the entire middle out of it, or channel it to match the manifold. Your thoughts on this are appreciated.

I was thinking that cutting the whole middle out of the spacer would be best, but didn't really know....

Jamie

Yes I will use the stock carb spacer. By stock I mean it will not be modified.

On the Hitachi 13B setups, the only channeled spacer I've ever seen was on a '78 carb. Lots of stuff was changed for the '78 carbs and the spacer was just one change in a long list of changes. While experimenting, I tried the carb with an earlier seperate runner spacer and a channeled manifold and the results were fine. It's currently sitting on a large streetported nitrided R5 engine in the GLC. It runs better than it did on the RX-4 so I must have done something right. The idle is a lot higher but it has a light steel flywheel and only a few hours of run time.

It was my plan all along to keep the spacer stock for the Nikki. I must point out however that if you were to cut channels in the spacer, it would probably hurt low end but give greater high end. This is just a theory of course. If you have two spacers you could try it both ways I suppose. I wouldn't try cutting the entire middle out unless you have three spacers.

I won't have access to this project after it's done, and it's an automatic so good low end is a must. Therefore stock carb spacer.

Now I need to find out how to vent the oil tube to prevent CAPuccino from forming. :) Which nipples can I block off and which need a vacuum line? If there's time I'd like to experiment with vacuum advance too.