Here is an interesting video supporting the use of an open spacer for all holley owners. Now this is a V8 dyno pull but you can see some relevant information. Personally, I would like to see someone try a tapered 4 hole mounted upside down (taper facing up) to smooth the transition and still have the open plenum on a racingbeat intake.

http://www.youtube.com/watch?v=i2DvnoHWagk

 

What not to do is use an open spacer on a square bore RB intake. I found that out, and it makes sense after you think about it hahah

 

Why not? Thats what Im doing and it made my car run better and fixed my problem of my secondaries not working.

~T.J.

 

I have a stockport 12A with a Holley 600. I don't really like the setup and I plan to switch back to stock or sterling.

With the carb going right to the intake, I got the car tuned okay, but it had quite a bit of hesitation when I got right on the throttle. Also, around 4500 it stumbled and maxed out.

I bought the open spacer and could not get the car to idle at low rpms. I think the lowest I was able to go was 1800 or so. When I hit the throttle it was nothing but stumbling. Yes I retuned it for the spacer. My thinking is that the Nikki has four ports which led directly to four ports on the intake, pretty much a square bore setup. I gathered that when I hit the gas hard with the open plenum, the fuel went in too fast. When the primaries open, it goes into all four ports on the RB intake, when I assume they should just go into two.

J9fd3s made this post to help me understand better; https://www.rx7club.com/showpost.php...65&postcount=8

My logic could be wrong, and I need to do more research on the Holley setup and the exact working of the intake on this car. I need to find a junk 12a and just tear it apart so I can learn hands on how they tear apart and the innards. Yeah pictures help, but I think most people here are more hands on.