JimmyHat

I dont know how long they have been like this, but just the other day i was blasting down the highway, and the car (84 gs, no emissions, msd direct fire, gutted interior, etc.) topped out at 85mph. So i lifted the hood and i had someone rev the engine to 6k. i looked down the carb and the secondaries didnt move. so i moved the linkage manualy and the rpms shot up.
I think its time for a yaw conversion.
Any help would be greatly appreciated.

P.S.
Also i was wondering can u run the vacume advances open. like unhook the vacume lines coming off the distributor?? what are the ups and downs on doing that?
thanx
kyle

diabolical1

iTrader: (3)

well, in the meantime, there is a lever attached to a spring (that should be attached to the rod that actuates the secondaries) sometimes it gets inverted, and that stops the secondaries from opening. it happened to me several times ... i'm sorry that i don't have the technical names for these parts, but hopefully someone with more knowledge will read your question and this lame-*** attempt to answer and know what i'm talking about.


good luck

oh ... i don't know how to answer the distributor question.

SilverRocket

Search the forum, there are numerous threads covering the causes and solutions of this problem.

MIKE-P-28

iTrader: (1)

If its time for a Yaw, I got a carb sitting right here you can send to him, so that your 3 month wait for your carb to return wont render you without wheels and rotary power

jeremy

iTrader: (1)

someone please buy mike's carb.

sponsered by jeremy

Sterling

...Yeah, Christ he is really pushing that thing!

JimmyHat-
You won't see your secondaries move in the driveway. They are vacuum operated, and will only come on under certain conditions; One of them being significant engine load.

Look in the archive section, and read my carb write up.

(Why does'nt anyone read my ******* write-up?!

I'm just kidding!!! But there's a buncha useful info in there that will help you with your Nikki carb, including how to wire up your secondaries to make them mechanical.

82transam

iTrader: (18)

Hey sterling; I read your writeup

Directfreak

iTrader: (2)

Me too...don't hurt me...but I like FI..



Sterling, why don't you put the link to that writeup on your Sig, that way you can leave it available for all to read and follow.

crankit

pull the spring out of the secondary diaphram and see if they open. if not its linkage problem most likely.

crankit

I actually pulled my spring out cut it in 1/2 then stretched it back almost to normal length. result comes in quicker but not all at once

JimmyHat

Thanx for all the replies everyone. Well at MZM motorsports, they told me that my secondaries are opening after all. I dont know, but topping out at 85mph doesnt seem right. And the car idles at 200 rpm. sometimes stalls out if i come to a sudden stop. And the car backfires like a SOB! It just doesnt seem like all the power is there. It runs alright on the highway- about 65mph, but one day i was racing my bro home (he was driving my infiniti q45= 310hp) and the car started getting a little on the warm side. It has a brand new radiator and just installed a '87 2nd gen oil cooler. So i kinda thought that it might be running a little lean. But i dont know, ill keep messin with it till i get it working again. But thanx again everyone.\
P.S.
Mike P, how much u want for the carby?? Is it any good?

Sterling

What you've done is more like having stuck a stiffer spring in there. Cutting a spring in half, and then stretching it does not make for a softer spring!!!

The result you are experiencing is that your secondaries are now coming on a bit later than they used to. The engine RPMs now have to be higher under load to create enough intake manifold vacuum to suck the secondary actuator diaphragm against a now tougher spring. The effect is that there is a sudden burst of power coming from the engine. What is in fact happening is a whole different story. By the time your engine has reached the required RPM under a given load to open the diaphragm, the flow going thru the carb required to feed the engine at that higher RPM is maxing out the already too small primary fuel jets, and you are beginning to run lean.
Increasing engine RPMs finally opens the secondaries on a flat stretch, and as your engine begins drawing air thru them, not as much flow has to pass thru the primaries, and your air fuel mixture returns to a more reasonable ratio.

You will not gain any more power by doing a secondary mod to the Nikki carburetor. The only thing you can do to it by monkeying with the secondaries is control how fast you get your engine to work that carb to its full flow potential.

Cutting a diaphragm spring and stretching it is NOT one of those things!

Vacuum operated secondaries are something I liken to having an automatic transmission in your sportscar. There's just no place for them for real driving enthusiasts! The vaccum operated secondary has its place among the masses, where "MPG may vary according to foot wieght...".
Think about it -With mechanical secondaries, where you CAN drive all day long never pushing far enough down on the pedal to open up the 3rd & 4rth barrels, you can have such a different MPG than if you stomp it everytime.

Vacuum secondaries keep everything as even as possible, and less control is given to the driver. The result is an MPG range that is much narrower (and thus more palatable to both salsepeople and consumers).

Everybody with a carbed Rx-7 should wire their secondaries. It should be the first thing you do!
The difference is amazing! I gaurantee you'll wonder why you spent the time ****** around with secondary diaphragm spring rates.

crankit

I sort of agree and disagree. Secondaries wired open will produce a bog until there is enough vacuum to pull the fuel. Thats why at least holleys have secondary squirters to take care of that which are not on these carbs. The linkage still does operate the secondaries opening but not until 1/2 throttle or more then its all up to the engine and setup you have as to when they start to pull the fuel in the secondaries. Now this is regular street driving not race track also. If there was a spring kit for the secondaries I think you would get more from that then wiring the linkage at least for the street. But everyone has their own opinion.

Sterling

[QUOTE]Originally posted by crankit
Secondaries wired open will produce a bog until there is enough vacuum to pull the fuel. Thats why at least holleys have secondary squirters to take care of that which are not on these carbs.

Read my write-up.

The linkage still does operate the secondaries opening but not until 1/2 throttle or more then its all up to the engine and setup you have as to when they start to pull the fuel in the secondaries.

So are we talking about modding the carb "just a little", or fixing these problems? Besides, the secondaries don't need to come open until the primaries are almost maxing out the fuel jet flow anyways.
Change the damn linkage to make them open when you want. It does'nt take genious...Hell; I did it!

If there was a spring kit for the secondaries I think you would get more from that then wiring the linkage at least for the street.

O.K. But that vacuum operated secondary will operate the exact same way every time, and will not always be adjusted to give perfect performance over the whole range of RPMs versus load versus jet size/bleed size, ect. No carburetor will...of course. However, if the secondary opening is "user controlled" (via yer foot), then it's a simple matter of learning how to drive the car properly.
You learn not to feed it too quickly, and when (under what load circumstances) you should feed it at different rates.
The more you drive it, the more you learn. Also, you can manipulate the behavior of your carb much to your advantage when there is a severe temperature difference. 30* difference is night and day to a carb.

Like I said; I liken vacuum operated secondaries to that of having an auto tranny. If you want full control, and are willing to learn to manipulate the car...Ya know - "Be one with the car..." n' all that crap- then mechanical secondaries are the way to go.

The bog is something easily overcome. (Like I say, read my artical.)
Just because Nikki made the carb as close to a performance/econo hybrid as they could does'nt mean you can't change the design just a bit!

**The part about beating the bog is simply installing a **** load of gaskets in the accelerator pump housing so as to max out the diaphragm capacity. (It can travel just a bitty-bit further than it does stock.) You get a bigger shot.
But then, you have to extend the actuator arm so that the shot lasts over a longer duration (squirts over a longer stroke so that it's still squirting when the secondaries are opening). It really works! And it's cheap, and TOTALLY reversable if you don't like it. You can "undo" all of it without so much as leaving a scratch on the stock carby! (I use that as a real selling feature because I know people are apprehensive to try something that might screw up their carb.)

Hey try it! If I can convince you, then I'm cooler than Directfreak!!! But ya gotta do both the mechanical wire-up to the linkage, as well as the accelerator pump volume increaser. Otherwise you will have that terrible flat spot without a doubt.


...TRUST me!

RIXSEVEN

You may want to check the valve on your engine. I am sorry if this is very general, but I don't know whether it is on the carb or the engine. It is black and Positioned "sideways" on the left side (right near the engine or above it) if you are looking down at the engine standing infront of the car. I replaced this part and my secondaries worked perfectly. I had almost the same problem as you, but I was not able to just pull the linkage and open the secondaries. I believe this valve has to do with some vaccum mechanisim. I do not know if this will help, but I am just trying to help.

crankit

Let me get this right Sterrling. You say that by giving an extra long shot of fuel via the accelerator pump you'll be able to dump enough fuel down the primaries to help the secondaries?

Sterling

Yeah, that's right!

It's like this:
The AP (accelerator pump) gives a squirt when you first open the carb (like it should). But on a stock Nikki with vaccum secondaries, they open very slowly because they are being opened by vacuum in the manifold, which increases with both load and as the secondaries are being opened. Ya dig?- Sort of a self-perpetuating process that takes a real long time when compared to the quick responce of mechanical secondaries.
Due to the fact that the secondaries are opened at such a slow rate, there is no need to introduce an extra shot of fuel from an accelerator pump into the carb.
However, mechanical secondaries very much do need that extra shot, or else tromping on the pedal will be introducing a giant gulp of air that is'nt "laden" with suspended fuel droplets yet. You have to remember that the fuel needs to be sucked up out of the jets and airbleed circuit by the draft of the air flow, so this takes a fraction of a second.
This is why you need a shot of fuel for the primaries; and so the secondaries as well.
Problem is, our spiffy Nikkis were'nt designed like Holley Double Pumpers. They have weedy lil APs that give weedy lil shots of fuel. If you take the top off your carb, and observe the AP shot as you move the throttle (AND move the secondary with it as the primary linkage "frees" it), you'll see that the shot does'nt last very long at all, and that there is no shot whatsoever by the time the secondaries are freed up.
So my mod is to lengthen the travel of the AP linkage so that it finishes its squirt by the time the secondaries finish opening. And it works, too. But you also need to increase the volume of the AP so that there's enough fuel in the shot to make a difference!

It's all in the write-up.
Didja read the friggin write-up?!

jeremy

iTrader: (1)

i have to disagree on stretching the spring. pressure required is related to coils and spring wire diameter not length.

Directfreak

iTrader: (2)

Hey now! What does that mean? Play Nice!

mar3

iTrader: (8)

Sounds on the money to me...

crankit

Well I just emailed this situation with the secondaries to Holley carbs. Lets see what they say.

rxtasy3

iTrader: (2)

When I used to run the stock carb, I wired the secondaries to work manually, now since I have a Holly on it now, I have a screw in it so it also works manually.

mojodaddy

jimmy hat, it sounds like you are runing ritch due to a vacume leak. check the tube going to the secondarys diaphram. its by the ehauxt manifold so it gets fried.

Sterling

mojodaddy, a vacuum leak would be introducing air into the carb, and would make the mixture too lean. "Rich" means too much fuel for how much air the carburetor is flowing at that time. Also, I think you are confusing another component with the vacuum secondary diaphragm box, as there are no tubes coming from it. It is located on the front passenger corner of the carburetor, up high.

[QUOTE]Originally posted by crankit
Well I just emailed this situation with the secondaries to Holley carbs. Lets see what they say.
[QUOTE]

I'm interested in what the folks at Holley have to say.
However, the information you seek as a reference can be found in any basic carburetor book.
I hope you did'nt include my carb mod write-up in the Email, as #1 It is [i]Nikki Carb specific, and #2 I believe I trash Holley carbs in that write-up!

I would like to see a copy of the Email you sent to Holley so that we can all see the question to their answer. Having an answer to a question we're all uncertain of how it was presented does'nt do much for us, as the asnswer can be too easily misconstrued from its original context.

And uh, just what was the question again?

crankit

Well heard from Holley . To start with I just told them of a car I used to have 80 Z28 with 40 over 350 3.73 gears with a 750 vacuum secondary holley. Asked if by wiring the throttle to open secondaries too and by giving more shot and longer duration with the acceerator pump if this would cure any bog. There answer was no. I didn't use the RX-7 but I don't think it really matters. If your in doubt write them yourself at carbs@support.holley.com