So on the Nikki carb we have the infamous shutter valve. Given that tehe rat's nest has been removed, and the two vacuum openings in the valce capped, should the shaft that sticks out horizontally out of it move when the engine is revved up? Mine does, and I'm trying to determine if the butterfly in the intake manifold is closing when I accelerate.

Notice that the shaft was moving only when the acceleration was sudden, not when it was gradual.

 

I should add that the shaft moves into the valve, and does anybody knows if that means that the butterfly is closing or opening?

 

I think the shaft is extended in the open position, and vacuum closes it.
My rat nest is also removed, but it's 1:am here at my apt complex, so I can't confirm the position of the shaft (and look like a normal person).

Try manualy pushing the shaft in while running, and see if it affects rpms.


isn't the shutter valve in the intake manifold?

 

yes it is in the intake manifold, i would just leave it open

 

Screw that just cut that thing out...it restricts airflow. While you are at it smooth out all the bumps in the intake manifold. And if you do deside to take it out make sure you patch up the holes really well.

 

Dude, don't just "cut the thing out". The manifold was designed with the butterfly in place, so if you remove it, turbulance is created.

The best way to deal with this is to remove the vacuum pot that actuates the butterfly, JBWeld the vacuum holes shut (so you don't have a huge leak in the manifold) and JBWeld the outside of the shaft to the outside of the intake mani, to keep the butterfly in a "full open" position.

Any other method of sticking this butterfly in the "full open" position will work, but this is the one I used, mainly because I didn't mind JBWelding my intake mani.

Off Note: JBQuikWeld is great... 6min to cure, and it's still strong enough for tasks like this.

Jon

 

I took mine out and have had no problems. In fact, by removing it my idle has smoothed out considerably. I noticed a larger difference in idle smoothness by removing that stupid butterfly than I did doing direct fire.

 

Carlos,
I know I still have pre-RX-7 12-A intake manifolds somewhere in my garage. But if you’re not rushing, you got it.

Mel

 

Thanks for the replies guys, I think on an immediate basis I'll try to immobilize it. Maybe JBweld the shaft?

Mel, thanks for the offer, I might take you up on it if you ever find it in your yunkyard . But my intake is also ported to match the engine. I would have to port that pre-7 manifold as well, right?

 

its not hard to match port it.

 

Alright, let me know when you find it and thanks.

 

QUOTE
Dude, don't just "cut the thing out". The manifold was designed with the butterfly in place, so if you remove it, turbulance is created.

The best way to deal with this is to remove the vacuum pot that actuates the butterfly, JBWeld the vacuum holes shut (so you don't have a huge leak in the manifold) and JBWeld the outside of the shaft to the outside of the intake mani, to keep the butterfly in a "full open" position.

Any other method of sticking this butterfly in the "full open" position will work, but this is the one I used, mainly because I didn't mind JBWelding my intake mani.

Off Note: JBQuikWeld is great... 6min to cure, and it's still strong enough for tasks like this.

Jon
QUOTE

The manifold was also designed with all sorts of bumps and ridges as well, but if you smooth those out you will get better airflow. By removing the butterfly how do you get more turbulance? That doesn't make sense.

People port out there intake and exhaust with greatly improved airflow, witch increases the output of the engine. But the car was made with the ports the way they are, why change them? The car was made with a verry shitty header, but why change that to something that flows better? Or the cats? The muffler? The carb?

The shutter valve is only there as part of the emissions. On deceleration it closes, which reduces the amount of fuel delivered to the rear rotor. That is about all it is good for. Remove it and weld or JB weld the holes closed, then smooth it out with a dremmel. You will be supprised.

 

Like ians I removed mine and am perfectly happy with it. Just pick up an intake gasket kit with the new o-rings because likely you wont be able to just unhook the screws on the butterfly (swear the bastards are welded) so you would be best off to remove the intake and drill out the stupid screws. On some cars when ya remove the rats nest the 20 year old butterfly will want to close under flow. Just rip it out if its not being used. After doing this mod ians car started idling smoother than i thought was even possible with a carbed 7.

 

I removed mine. I didn't use jb weld, but steel weld intead. It's more of a putty consistency and you can work it with your hands (with nitrile gloves on of course). jb weld is too runny for some things.

fwiw, the screws on the butterfly can be a beyatch to remove. I had to drill mine out, which is tricky doing it with the manifold in the car still. If this happens.. plug underneath of butterfly with a papertowel, and very carefully drill out the screws WITH LOTS of bar oil on the drill tip, clean the tip often.. then vacuum the hell out of it. remove butterfly, and vacuum again. Remove paper towel. The rod is too long to be removed with the manifold in place unless you pull it out a little bit, and cut it off, then remove the rest of the way. I used bolt cutters... :-d

dale

 

did you find that intake manifold Mel? if not, I'm removing my intake manifold this weekend and handling that butterfly. The manifold was due for a gasket replacement and new o-rings for the cooling passages anyways.

 

Its too cold at night. mid-50's is too cold for me. maybe tomorrow I will call ya.

 

Ok so since Wacko didn't come through , I removed the intake manifold today and got to work. Did several things with it. 1) Removed the pipe that goes to the - nonexistent - cat, and installed the block off plate. 2) Drilled out the screws that hold the butterfly and removed it along with the shutter valve. 3) Then used 19 oz of carb cleaner in spray form to get rid of the metal shavings and all the dirtiness accumulated over time. Nasty stuff, carb cleaner, but it will dissolve just about everything. 4) JB welded the holes left by the shutter valve. 5) Installed new gasket for manifold, and o-rings for coolant passages (it didn't have any installed!). 6) While at it, also removed the AAV from the carb, and blocked the port that goes from the manifold to it.

Tomorrow, install in the car and test drive!

 

Shoot your engine installer!!! I wonder who would that be???

 

El gordito! But he knows now and has learned from his mistakes.

 

OK so I installed the whole thing, ironed out couple of leaks, and went for a test drive. Unfortunately it rained all day today so couldn't do a full test, but it definitely felt more umphy and responsive. I hadn't broken traction in 2nd before (not a chirp, but actually breaking traction), not even on wet with the 215s.

 

carlos
I found the manifold but Im not sure if its a 79 or pre-RX7. come by and pick it up. a little too late but hey much better than the 81+ intake manifold.

mel

 

Alright, guess better late than nevah! I'll swing by next weekend.

Oh, and I was driving the car today - oh yeah. It's amazing the difference, specially WOT in first, change to second, WOT. Before, when shifting to 2nd, there would be a lag, due to flooring it and thus closing the butterfly. Now, no lag. I gotta redo my 0-60 now