1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Carb spacer plate on 12a?

Old 03-17-10, 08:10 PM
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GA Carb spacer plate on 12a?

This may be a dumb question,but its been bugging me.I have friends that are v8 all the way.All of them use carb spacer plates.Will this give a rotary any added hp?
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Old 03-17-10, 08:19 PM
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I've read that an extra spacer between the carb and manifold will help a little, if there's enough room, along with cross-cutting them from primary-secondary on each rotor.

Last edited by Oneiros; 03-17-10 at 08:28 PM.
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Old 03-17-10, 08:56 PM
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Originally Posted by Oneiros View Post
I've read that an extra spacer between the carb and manifold will help a little, if there's enough room, along with cross-cutting them from primary-secondary on each rotor.
Thanks,i am going to find some info if any.I would have to change breathers if i went that route.
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Old 03-17-10, 09:43 PM
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Nope, no difference with a nikki. However it does make a difference adding an open spacer to a holley or edelbrock on a racing beat intake.
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Old 03-18-10, 04:52 AM
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Originally Posted by 84stock View Post
Nope, no difference with a nikki. However it does make a difference adding an open spacer to a holley or edelbrock on a racing beat intake.
I have 465 Holley with a R/B Intake.Those spacers are not to expensive so i may give it a try.Thanks.
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Old 03-18-10, 09:55 AM
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Adding a spacer effectively changes the intake runner length. By making it longer ie. adding a spacer, you change the power band. RB says even on thier IDA setups that adding a scacer will lower your powerband by 500 I believe it is. Not sure of the specific data on the Holley, but the principle applies across the board. Let us know how it performs with versus without the spacer, and what thickness etc. you use.
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Old 06-24-10, 10:51 AM
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Okay, I know this is a super old thread, but I need a question answered.

First of all, I know, I have heard it numerous times before, a Holley 600 IS TOO BIG. I get this. It's what I purchased from a member saying it worked great on his car before I did any major research into it. It's been nothing but a headache. Oh well, last time I'll ever do that.

After reading this thread and a few others, I purchased an open spacer. It's only after I purchased that I realized the RB intake I have has four seperate 'ports'. The open spacer obviously has no ports, causing the air and fuel mixture to be screwed up for the primarys and secondarys.

After I added the spacer, my car would not idle until I readjusted the carb. I readjusted it, and then began the problems. On hitting the throttle in neutral, it would bog unless I gradually hit the throttle. Punching it almost made it seem like it wasnt getting gas. I know it was because it was backfiring through the carb itself.

I'm thinking a square bore with the four ports would work better than the open. I guess I could spend more money and find out, right?

Any input is greatly appreciated!
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Old 06-24-10, 11:17 AM
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Originally Posted by chris_g View Post
Okay, I know this is a super old thread, but I need a question answered.

First of all, I know, I have heard it numerous times before, a Holley 600 IS TOO BIG. I get this. It's what I purchased from a member saying it worked great on his car before I did any major research into it. It's been nothing but a headache. Oh well, last time I'll ever do that.

After reading this thread and a few others, I purchased an open spacer. It's only after I purchased that I realized the RB intake I have has four seperate 'ports'. The open spacer obviously has no ports, causing the air and fuel mixture to be screwed up for the primarys and secondarys.

After I added the spacer, my car would not idle until I readjusted the carb. I readjusted it, and then began the problems. On hitting the throttle in neutral, it would bog unless I gradually hit the throttle. Punching it almost made it seem like it wasnt getting gas. I know it was because it was backfiring through the carb itself.

I'm thinking a square bore with the four ports would work better than the open. I guess I could spend more money and find out, right?

Any input is greatly appreciated!
the "carb sizing" you've read on here is incorrect. the formula used is for an open plenum type carburator, where there is a "box" or "plenum" all of the cylinders feed from after the carburetor.

what this does is smooth out the pulses of the engine, and the carburetor sees a relatively steady demand, and since it sees the average of ALL the cylinders, the carb wants to be smaller.

as you've noticed though, the rotary is not setup this way, it has a separate port for each barrel. its basically an individual runner intake.

in an IR intake each barrel of the carb feeds each port/cylinder of the engine, and these carb's need to be bigger as they have to meet the instantaneous demand from the engine. the flow is not steady.

so a 600cfm holley is big for a stock 12a, but maybe not too big as the cfm rating, doesn't really apply, its better to look at the throttle/Venturi sizing.

so back to reality.... and off the shelf holley is setup to run on a plenum, RB set's their holley's up to be IR carbs, and you can't mix and match, as the jetting is different between the two.

if your carb ran great on the IR manifold, then you need a 4 hole spacer. if it ran great with an open spacer, then it needs to keep an open spacer
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Old 06-24-10, 11:31 AM
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Wow, thumbs up to you. Thank you SO much for that information.

It did run good without the open spacer, so I think I will purchase the square bore one.

Thanks again man, it is much appreciated and I think you helped out all people who want to run a spacer with their Holley setup. You really clarified that!
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Old 06-24-10, 02:04 PM
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Originally Posted by chris_g View Post
Wow, thumbs up to you. Thank you SO much for that information.

It did run good without the open spacer, so I think I will purchase the square bore one.

Thanks again man, it is much appreciated and I think you helped out all people who want to run a spacer with their Holley setup. You really clarified that!
you're welcome. i didn't figure it out though, afik peejay did?
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Old 06-24-10, 06:24 PM
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I purchased the 4 port and it works much better. Now I just have to play with the tuning again. Idles and slow[er] acceleration is fine. When hard acceleration it seems like it lacks fuel at first, then around 5500 it starts to stumble. There are a few things I will play with still.
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Old 11-16-17, 01:21 PM
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Spacer on a 12a

So I have a 85 Rx7 12a stock engine I wore brushed and polished the intake and the intake holes I've been using a 600 Holley four barrel for years with a racing beat intake and recently my carbs throttle linkage runner that goes through the base plate of the carburetor started letting air in so I got a 650 blp Holley carburetor but it's air flaps we're way bigger on the rear than a regular Holley carburetor so I got a spacer that I can do open or individual I chose the open one hopping for no issue found out it's bad because it messes up the fuel air ratio mix up and makes it backfire and all this other crap the car runs way better and idles now but right when I first get on it or if I'm cruising and I request more gas it would back fire simply put short i dont know if the spacer is benificial or not but I am a professional mechanic in Florida wanting to know if I should just keep the spacer and put the individual hole piece that I have for it in the spacer or should I just hog out my intake and put the carburetor back on the intake and cool little information for other rotary fans with 12a's you can take your throttle linkage off the Nikki carb and put it on the Holley carb so you don't have to use zip ties or something but if someone could please let me know a good professional opinion that would be great sorry for no grammatically correct typing was on lunch and had little time to do this thank you
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Old 11-16-17, 02:20 PM
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When you can take the time to post something readable, we can take the time to read it and try to answer.
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Old 11-16-17, 06:10 PM
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Look I just wanna know if someone has tried either way. Success or not, is it better having a spacer and the barrels being separated? Or is it better to just hog the intake? What will make more power?
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Old 11-16-17, 08:35 PM
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Search threads by jeff20b and you will find the answers.
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Old 11-18-17, 05:13 AM
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What are you even asking?

The 650 is too large for a 12a. Period.

The 600 was also too large.

Why would you want to zip tie the linkage on a 650?

Components from a Nikki are not compatible with a Holley.
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Old 11-18-17, 05:19 AM
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I also know exactly which spacer you're talking about and I suggest you throw it away. They're garbage.

buy a dedicated 4 hole spacer.

If you want to experiment with a well known old trick, use a thick open gasket over your 4 hole spacer. This doesn't impede airflow or create turbulence, but equalizes the vacuum across the carb.

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