RotorMotorDriver

iTrader: (1)

Ok, so Im a complete newbie with Holley carbs, but Im far from incompetent I would hope, haha.

I have what was sold to me as a Racing Beat Holley street port kit which has a vacuum secondary system that isnt working. I verified this twice by using both the bread tie and the paperclip tests (putting each on the vacuum pot shaft and driving full throttle through 3 gears), there was no movement at all.

I pulled the secondary vacuum pot and discovered the diaphragm was leaking (compressed shaft, held port covered), so I took it to a local muscle car shop and they got me a new one. They also got me new metering block and bowl gaskets about a week earlier as the carb had the wrong ones on it when I bought it. I also picked up a yellow secondary spring (very light) while I was there. I blew some light compressed air into the vacuum port, and air comes out the hole under the butterfly in the primary venturi, so its not clogged. I read about a hole possibly in the secondary venturi also, but I didnt see/hear one?

I got home, installed it all, and repeated the test. No movement still. I pulled the whole thing back off, put a new o-ring between the carb body and the secondary vacuum pot, reinstalled it all, still no movement. With the engine off and the throttle held wide open, the secondary linkage and butterflies move freely and easily, no binding at all.

Here is a link to the carb kit (which was bought used):

http://www.racingbeat.com/Mazda-Perf...rtNumber=18034

It also has these float bowls:

http://www.racingbeat.com/Mazda-Perf...rtNumber=16641

It does appear as if it has aftermarket metering blocks also since I can change the jets on both the primary and secondary sides, and Ive been reading the RB metering blocks have the jets built in. Also, it has the quick change secondary spring kit, and no check ball in the housing, but I read thats normal for RB carbs?

Vacuum advance is hooked up and running off the ported vacuum port on the metering block, manifold vacuum was running to a PCV valve, however I tried blocking off both the PCV valve as well as advance and trying to repeat the test hoping that maybe a leak in one of those two setups that was preventing something from happening, still no dice.

Im running a Holley blue pump and regulator, fuel is set to 6 PSI, float levels are correct. As I said, the carb was bought used, so its possible someone mucked with something, but it seems like a fairly simple system, and I dont get why it wont open the secondaries...

Thanks in advance!

~T.J.

Oneiros

OK I am a Holley noob as well. But I know my Nikkis. One thing you could test is to see if there is vacuum in the line leading to the diaphragm, or the diaphragm box itself. Is there any way you could tap into it with a vacuum gauge to test it? The amount will only be small ~1PSI but its still noticable.

P.S. what is this "paper clip and bread tie" test. It sounds useful for testing the operation of secondaries...

teddyrx2

iTrader: (33)

post a pic of what you have...so we can see your carb...

RotorMotorDriver

iTrader: (1)

There is no line leading to the diaphragm, its an internal passage.

As for the paperclip test, below is a Googled image. I dont bend the clip to fit the rod like the picture, I just clip it on the same way you would clip it on papers.

Basically, clip it on, slide it up to the top of the shaft so its touching the vacuum pot and take it for a drive. If the shaft pulls up to open the secondaries, the clip will be pushed down the shaft (as shown in the picture) and show you how far they opened.

This is also useful for seeing if the spring in your vacuum pot is too hard (not opening all the way). The bread twist tie works the same way, or a small zip tie snug but not tight. I prefer the bread tie/zip tie because theyre smaller and seem like they wouldnt get in the way as much towards the end of the stroke if the secondaries are in fact working.

~T.J.

RotorMotorDriver

iTrader: (1)

Anything specific you would like to see? These arent great, just what I had on hand already uploaded. Theyre also not current as I have since hooked up the throttle cable with the linkage pieces, replaced the return spring, took out a plug on the primary metering block and added a 1/8" NPT to 1/8" barb for the vacuum advance. I also finished the fuel lines with clamps and things. These are just pictures of the mock up/install process from my build thread. I was told the OMP linkage was removed in favor of premix (which Im also running). It came off a car with full RB street port exhaust which I also bought and am running. Oh, and the choke has been removed also.

~T.J.

RXnos1200

iTrader: (24)

use the lightest secondary spring. The ones on the carbs I used to race and tune with were white or no color. Hardly any resistance at all.

The vaccum secondaries just seemed inconsistent so I always made my setups to the double pumper ones......

try changing the spring.......they make a big difference even though the resistance seems similar between the colored springs.....

rxtasy3

iTrader: (2)

there's alot about that carb that tells me it's not from rb. specifically how the throttle linkage where the cable would connect to looks. the vac pod doesn't look the same either. keep in mind this is comparing how urs looks to mine.

RXnos1200

iTrader: (24)

^^^^^ its been modified by the previous owner.......

RotorMotorDriver

iTrader: (1)

I have the yellow sping in it now, the lightest one they have. White is heavier.

Also, its been modified as I said. The throttle linkage is hooked up with the same pieces I've seen on other RB carbs (the two flat pieces), and the vacuum pod has the quick change spring cover on it.

I will take some pics specific of the carb today. Thanks everyone.

~T.J.

RXnos1200

iTrader: (24)

In my kit the white is the lightest......this is from the Holley kit 20-13

COLOR
RELATIVE LOAD
350 CID ENGINE
OPENING RPM
402 CID ENGINE
OPENING RPM
Initial
Full
Initial
Full
White
Lightest
---
---
---
---
Yellow*
Lighter
1620
5680
1410
4960
Yellow
Light
1635
5750
1420
5020
Purple
Med. Light
1915
6950
1680
6050
Plain
Medium
2240
8160
1960
7130
Brown
Med. Heavy
2710
8750
2380
7650
Black
Heavy
2720
Not Fully Open
2390
Not Fully Open

84stock

iTrader: (5)

What is the list # off the choke tower?

I hope you are running premix or have your omp wired open.

84stock

iTrader: (5)

You may simply be over carb'd. Provide all details on the engine and again the carb list #. Your carb pics are missing the racingbeat omp activation rod.

I run a holley 670 avenger on my supercharged 13b, purple secondary spring and I use the quick fuel secondary diaphragm. I am dialed in almost perfect. For ***** and giggles I tried a 870 avenger once, even with the lightest spring it only pulled the secondaries open once.

84stock

iTrader: (5)

A phenolic open spacer of any size (even 1/4") will make an immediate improvement. Don't use a hardwood one, this is what most people crack holley baseplates with.

RotorMotorDriver

iTrader: (1)

I dont know why, but it never occured to me to look into the fact it may not be a RB carb - I dont think it is. The list number is an 1849, which makes it 550 CFM. Id say thats my problem, the carb is just too big and there isnt enough intake velocity to create vacuum to pull them open.

So now the question is, what do I do with it? I have all the parts to drop a 465 CFM (1848) on there, but its not "modified" by RB. I can get a brand new 1848 for about $200 less than buying JUST the carb from RB.

When I called RB and explained the situation, they told me they do a lot of custom machine work on the metering plates, making new passages, blocking off others, getting new parts from Holley, making their own parts (linkages), etc. I dont know how much of that is true, but it makes me wonder about one thing - if they modify the metering plates (which dont have changable secondary jets), how can I tune my secondaries? Not everyone is at the same elevation, and not all motors run the same after all. I would never buy an "off the shelf" kit and expect to not have to do SOME tuning on it. Wouldnt I have to swap to different metering plates, thus eliminating their "modifications" in essence? I dont think they do anything to the bowls either (except add the fittings for the OMP) since the race float bowl conversion they sell would eliminate those modifications as well.

Basically Im almost tempted, as much as Ive seen it bashed, to just get an off the shelf 1848 465 CFM Holley body, slap it on, swap my metering plates, race float bowls, fuel lines, quick change spring kit, etc on it and start tuning the thing. It just seems like thats the most cost effective way to get it going seeing as I have ALL the other parts to support a Holley on a rotary. I used to run a 45 DCOE on my last motor, but getting back into that setup would be even more money I dont want to spend on this thing, lol.

~T.J.

RXnos1200

iTrader: (24)

yup he mentioned that he was premixing.......nice setup you got there 84stock......

RotorMotorDriver

iTrader: (1)

Forgot to mention its a Pineapple rebuild bought used about 3 years old. 85 PSI on both rotors, intake irons are street ported, exhaust is not (I know, lol). Im running the Holley setup above, plus the RB full street port exhaust, Holley blue pump and regulator at 6 PSI.

Everything else is golden really, seems like a good strong motor, no leaks, no smoke, good oil pressure, etc (knock on wood). It runs pretty damn good for running on 2 barrels, but I bet it could open up more in the mid-upper end. Low end is pretty good actually.

~T.J.

84stock

iTrader: (5)

Trust me, "try an open carb spacer" before you make any rash decisions!!!!

I would suggest a wideband at some point to help tuning. Yes you need to swap out secondary metering plates to adjust secondary fuel, however you can buy a rear metering block kit and just change jets to do the same.

If you decide to replace the carb, go with an edelbrock 500cfm "thunder series". You get the functionality of mechanical secondaries plus infinite adjustability of vac secondaries with the turn of a screw driver. Adjustable jetting for primary and secondaries and the metering rods make adjusting and tuning the primaries a snap, never have to touch the fuel!

vmarx7@yahoo.com

iTrader: (37)

put the check ball back in the secondary housing
try the stiffer yellow spring
check to make sure the diaphram is sealed properly which is diffucult with the quick change setup
test it by sucking on the hole where it mounts to the carb there should be a round cork gasket
if sealed correctly it should move the lever into the housing
secondaries only operate when driving not free revving the engine

RotorMotorDriver

iTrader: (1)

I guess I could look into the carb spacer. It seems that letting the mixture collect before it goes into the runners (so they all see the same thing basically) might be good anyway, and then vacuum would form on both sides of the rotor and possibly pull more air in I suppose.

As for the check ball, I was thinking of trying that, but I don't have one - never came with one. I will see about getting one when I go to the shop to see about the carb spacer.

Also, putting a heavier spring in doesn't seem like it makes sense. If they can barely open with no spring at any RPM, a heavy spring won't do anything but hold them closed I would think.

Thanks for the other tips, but I already said I did all that. That's the point of the paperclip and or bread tie tests I was talking about. Also, I said there is an o-ring between the vacuum pot and body, not a cork gasket. I would think an o-ring seals
better as long as it isn't compressing so much as to block the port, but I would think its not because I do get some operation from the secondaries with no spring.

~T.J.

84stock

iTrader: (5)

do the spacer and tell us the results

84stock

iTrader: (5)

BTW, check for hood clearance, the taller the spacer the better. If you have room for a 1" than go for it! Naturall hood clearance is no longer an issue for me

teddyrx2

iTrader: (33)

He can use a 1" spacer just fine hood clearance isn't a problem...

RotorMotorDriver

iTrader: (1)

I dunno about that, it looks pretty close with the air cleaner assembly. I will check it out and see what I can do with this thing...

~T.J.

84stock

iTrader: (5)

Put a 1" thick wet sponge on top of the air cleaner, shut the hood and look for a wet spot. Then use a thicker one and see. You get the idea.............just like teasing a woman, once you find a wet spot you know you're do'in something right.

RotorMotorDriver

iTrader: (1)

Well, I picked up a 0.5" open phenolic spacer and slapped it on. Wouldn't you know it, it runs way better and the secondaries are moving! The idle smoothed out and overall drivabilty has gone up 10 times what it was and I haven't touched an adjuster or jet yet. Time to start jetting this puppy!

Thanks for the tips everyone! I will continue my saga of learning the Holley and jetting I'm sure, lol.

~T.J.