Racingbeat Holley or rotaryshack Weber or unknown 48 Ida
 

Hey guys,

I'm in doubt here and want to upgrade my intake but can't decide wat to buy.
On the one hand the racingbeat Holley witch has to be a reliable choise because it's from racingbeat :nod:

On the other the rotaryshack Weber 45 dcoe with the long intake witch I like more for the looks but don't know if it is as good as the racingbeat

Also I have an 48 ida on the shelf that came of an bridge ported engine but it needs to be rebuild. I think it maybe to big for a stock port.


So the main question is: has anyone one of the above carb and what do you think of it?


My current setup in an stock 12a with racingbeat long primary exhaust.

my experience has only been with the rb holley kits. never had a problem the 465cfm setup for stock port 12a, but it's one of the early setups from back in the day. others will say their shit. maybe something's changed since then. only thing i hate bout them is since they sit sideways from the norm when sitting on a v8 intake, u get fuel slosh on hard cornering. the 48 would need to be rejetted for the stock port. they're all out there being run successfully. there's many threads here on this, even suggestions on starting point with jets and such.

First thing you need to tell us what the intake system is going on? I assume it's a 12A.. Is it ported?

It's a stock 12A with racingbeat long primary exhaust

I just ordered a Rotary Shack 48mm Weber for my half bridge. It was about $200-300 less than the Racing beat Weber set up. The one for the stock port 12A is less than 900 Rob can send the system to get polished too.

Build a hogged Nikki and save cash

More power, better fuel control, better mileage, more reliable

Make it fuel injection

Nikki is better than fail injection, lol.

That is also an option but here in Europe aren't any companies that I know of who can do the machining

all you need in the way of machining is a lathe to the venturi. The rest is all done with a dremel

I've done some searching this morning and found some topics about hogging out the nikki from Jeff20b I will go that route but first I have to solve some translation issues haha

I like the idea of saving the cash and I have a couple of nikki laying around

Good. It takes some time to do, but it's much better than anything you can buy out there at the moment.

I started playing with manifolds and such recently and I think it could be the answer for NA 13B too...

The nikki isn't hard and you don't need a lathe. I did mine all with a dremel or drill.

I've done mine with a die grinder for rough cutting and final shaping, and a dremel for finishing. But with anything that requires skill, I'll use the old saying, "it's all in the wrists." That means you only get good at it if you do it a lot to develop the skills to do it well. I recommend just using a lathe at this point. :)

I will ask a friend if want's to make the veturis. He works at a metalshop so it probably won't be a problem.

Cool. One piece of advice is to use the little hole as a landmark and make the narrowest point at that hole. The narrowest point should range from 23mm to 24mm. Don't go bigger or smaller. Then blend the narrowest point up to the top at a steep angle, as well as down to the bottom of the venturi at a much longer length. Keep them straight. Don't do the rounded lazy curve like Yaw was known to do. The Nikki seems to like a slightly sharper shape. A little rounding and smoothing right around the little land mark hole is fine. Make it kind of mimic the stock factory shape but not straight like they did it. Remember they mass produced these and had to speed production in any way possible etc. Because yours are one-offs, you can take your time and do a good job.

I've been scavenging for the right parts but it seems that all my nikki's have 90 airbleeds maybe that's because I'm in Europe and that will need an different tune?

I also have one with a much smaller primary top.
I will take that one apart to see what airbleeds it has
Attachment 611699

the smaller top, 81-85 actually flows more. the early one is not as good.

we had a racing series in the 90's using a stock 12A, with stock carb, and stock manifold and so there was a lot of testing done to see which bits worked the best. you want the later carb. the 84-85 exhaust manifold was better too, but a header is better than that. 2.5" exhaust is more than enough. our series, Pro7 made us keep the stock air cleaner, and it works best with all the flaps removed and ducted to cold air. drilling holes hurts power.

we weren't allowed to touch timing, but we were allowed to tune and mod the stock carb, which is where Paul Yaw got his start, although people had modded the stock carbs before him.

with a fresh engine (new rotor housings) 116rwhp was possible, 112rwhp was about average. a header adds 10hp. the euro rotor housings add another few hp, as they close 10 degrees later than ours did, so they were the cheater setup for a bit, N210-10-100

The smaller top one is from a 6 port 12A. I have that exact carb. It does have 90 air bleeds as well but they are different below the screw head. It has one extra emulsion tube hole that no other model had. Its primary venturis are also a VERY tiny 18mm compared to all other Nikkis with 20mm primaries. The secondaries are normal 28mm but you notice the boosters are different with a brass tube that extends across it. The baseplate also lacks an idle air bleed circuit making the carb hard to tune. I drilled one accurately on mine and it works. But it was incredibly risky. Had to go about 1.5 to 2 inches deep if I recall correctly. Then plug the access hole I made. Not recommended for the faint of heart.

That 6 port top is also not worth using for performance as it lacks the fuel rail the other tops have. This limits fuel as it must flow through the little drilled "galleys". Yo notice it also has a water choke. Or rather a coolant temp controlled choke instead of a cable controlled one. Lame. I swapped all of that over to a traditional cable controlled fast idle, and got rid of the choke flap valve as all the idle circuits I do are recalibrated not only to run better and work better than factory overall, but to remove the requirement for a choke flap valve in the first place. :) Plus they are kind of restrictive when you want air to flow through these like a performance carb, which the Nikki is if modded properly.

If you have a way to drill your regular 90 air bleeds to accept a pilot jet, drilled to 70, the carb will runs 100 times better. Even a holley dominator air bleed at #27 should work as that is the SAE equiv of about .70mm if I have my numbers right. I still have yet to order any and try them.

Just so you know, the large opening of all 79-80 and older carbs is bad for boost. Too much turbulent air creeps down the walls and encounters the air bleeds. This leans out the circuits too quickly and doesn't work right at the top of the primary's range. You need to find a proper 81-85 top for these two reasons: the smaller primary opening doesn't hurt flow and does provide a shroud over the air bleeds which prevents turbulent air from messing of the primary circuit at high RPM, and b) there is a little air deflector in the casting above each secondary air bleed. Check your 6 port Nikki's top for the deflector to see what I'm talking about. I just looked at mine, and yep it's there. I'm sure yours has it too. Too bad the fuel inlets/galleys are so tiny though.

I already have a 1984 one dismantled but can always doe the small one if that is a better option

You need a set of these to recalibrate your idle circuit. Just install them in the holes on the primary side of the carb. Genuine Mikuni CV Size 120 Air Jet B42 55 120 | eBay

Then you need a set of these to correct your 90 air bleeds into something that actually works better at around .70mm. You will need to accurately machine the air bleeds. Holley 126 27 10 Air Bleeds HP Dominator 027" Set of 10 | eBay

Then you need a set of these for your secondary air bleeds to help get rid of the annoying bog these carbs can get if you do mechanical secondaries and try to open them at anything below 4k. Who wants to wait that long? I floor mine at 3000 and can floor them at 2000 but it doesn't add any power that low. It just doesn't bog though. :) Holley 126 31 10 Air Bleeds HP Dominator 031" Set of 10 | eBay

Be sure to look up the accel pump mod as well, in my writings.

As for the fuel jets you will need, get them here. These are great for primaries sizes. HITACHI main jet 4H7-14984-40-00 4X7-14984-41-00

There is a tremendous amount more info you need to know in order to do these carbs correctly, but for now this will help you.

Use the 84 carb. Please. :)

You're right on the 6 port nikki it has smaller primary and the secondary venturi booster has a tube running trough it. It also has no idle screw so I will stich to the one I already dismantled

Thank you for the information I will let it sink in and will post the progress I'm making

Searching for tools at the moment. found this

https://www.jurgensmotorsport.nl/all...-12-stuks.html

wil call him tomorrow to ask what the steps are, it only 12 pieces

I'm also doing some studying about how the stock nikki works so I can get an idea what I'm changing. I've had the basic carburation training in school but that's long ago so I have to refresh my memory

Also comparing the nikki ' s i have to be sure I'm using a 84 one and it seems like it

My friend at the metal shop thinks he can hog the primary venturi so I wil bring them later this week

So all in all I'm pleased and hoping for the best

O I have to search for the rebuild kit also will do that tomorrow.