Spinner-D(eluxe)

I have been receiving questions from people about my carb since I posted some pics of my new Racing Beat Intake/Holley carb kit install. I have to admit I am not a carb expert (I know very little). All I know is it's a 4 barrel 650cfm carb. I know how the choke works, and hwo the secondaries are suposed to open up when enough vaccume is created by air rushing through the carb, but I am not sure my secondaries (secondary flappers) are opening? At what RPM about do you think they should open? I am wondering if maybe the actuator that opens the secondaries has a bad diaphram, or not. Would the secondaries open by blipping the throttle up to 7000 and letting off, or do you need to susstain a high RMP liek 6000RPM or something? Forgive my ignorance please.

FB II

they usually open up under load; as in you need to be driving it. make them mechanical for a couple runs and see if the car pulls harder at top end. then you'll know for sure!

Sterling

Spinner-D(eluxe), Holley sells an assortment of diaphragm springs that will change when your secondaries open. If you feel they may not be opening when you would like, buy the assortment and start playing.
I do not know how much they are. I do not know if you need an assortment kit that is specific to your carburetor model, either.

Rx7carl

Yes, the spring kit is applicable to all 4160 family of carbs. Spinner, 650? What motor and porting do you have? Wanna know if the secs are opening? Disconnect the link from the rod that acuates them, or disable them somehow, then you know they wont open. If the car drives the same, then youll know. I will say that a stock port 12A will probably not flow enough air to open them on a 650. Maybe a little, but not much I'd imagine.

rxtasy3

iTrader: (2)

He must be running a bridge port since RB's Holley setup for BP is 650. Street port uses a 600, what I'm using, and stock port is 465. I have a screw in mine so the secondarys open manually at about half throttle.

Spinner-D(eluxe)

I have a 13B with no porting. I have a Racing Beat Header, and Street Port Exhaust System. I'm planning a Street port someday when I rebuild my engine.

Spinner-D(eluxe)

How did you do this? YOu put a scre where?

Spinner-D(eluxe)

The Holley Carb that I got is the 600cfm carb. I called Racing Beat today and talked to one of the tech guys who was very helpful, and patient with my lack of experience. He told me the secondaries will only open when the engine is under load. Just revving the engine while in neutral won't make them open even if revving up to a high RPM.

I also asked him if I could use the 600cfm carb if I got a street port, and he said the carb was designed for a stock 6-port, and if you wanted to use it with a ported engine you could get front and rear side housings off a 12A, and a 13B 4-port manifold to make a 4-port 13b, and the 600cfm carb would be a good fit for that engine. He said a 4-port 13b can make more HP than a 6-port.

Anyone want to expand on that? I hope I relayed everything correctly.

Rx7carl

Yes he's correct. Its airflow through the primaries that makes the secs open. You wont get enough air just sitting still.

What hes saying is to use the 12A irons to make it a 4 port 13B. 4 port engines are better suited for SP. Also you will eliminate the 6th port actuator crap so youll end up with more potential airflow.

813KR$

To check if the secs are opening, just put a screw in your linkage and make the secs open mechanically. Then drive it and see if it runs better or not. The screw goes on the back side of the carb where the throttle cable conects, where the linkage of the prims connect to the secs their is a slot that allows the prims to open and the rod will slide not allowing the secs to open. If you put a screw in there to stop the rod from sliding, then when the rod hits the screw it will pull open the secs mechanicaly. If you dont understand what I wrote, I will take a pic for you.

sgieldon

Pictures are worth a Billion Words!
Could Ya?
Would Ya?
I'm sure there are a few of us Rotor Nuts that would like to see this setup.
Does it work with the RB Holley Carb.
Thanks
sgieldon

sgieldon

I guess I should have read the Thread. DUH!!!
Thats what the sub was on (Holley).
Brain Dead
sgieldon

813KR$

Yeah it will work on the RB Holley. A Holley is a Holley! Give me some time and I will post it, I think I may have already posted it once, but I will do it again. I dont remember the thread I posted it on.

Spinner-D(eluxe)

i understand perfectly. thanks!

813KR$

Screw Trick Pic:

http://www.tamparacing.com/gallery/s...=7&thecat=3018

Brandt

ur from tampa so am i I usally go to sunshine speedway what about u.

813KR$

You know me! I met you a couple weeks ago, at sunshine. I got the blue Rx-7 with the hood that looks like its open. Unless their was another Brandt out there with a 79 bridge ported Rx-7?

Brandt

Oh wassup man thanks for the info on this site. By any chance do u know were i can find a 2 and one-eightth socket for cheap. And on the direct fire should i run the msd or should i run the way jeff20b says to run it.

813KR$

MSD is More Spark for a longer duration and doesnt weaken as the rpms increase! You decide.

Sears has the socket for cheap! ! ! If you need one asap I got one. Just get with me. I emailed my cell to you.

Brandt

My e-mail addres is not working for some reason so i wont be able to find ur number is there any other way i can get intouch with u. Will u be at the race's tommarow cause if u will u can give me ur cell number there. And maybe u can let me borrow that socket. I just dont have $20 dollars to throw into a socket at the time.

Spinner-D(eluxe)

Well I finally did the screw trick on my RB Holley Carb, and felt the power of the secondaries coming on. The car really rips, but has a slight surge, or jerk when the secondaries come on. I still can't get the secondaries to come on with vacuum alone. I bought the spring kit and a spring quick-change kit so I can change springs in about a minute. I have tried all the different springs, and tried running the car with and without the ball bearing which cause some restriction (you know what I mean if you have taken apart a Holley secondary diaphragm assembly).

So my question is what Else is there to check? I believe the rubber diaphragm is in perfect condition, because i did a vacuum check on the assembled diaphragm assembly/actuator. The only thing I can think of is maybe I have a vacuum leak between the carb and manifold, but the engine runs smoothly at idle, so I doubt I have a vacuum leak.

If I can't figure it out my only other option is to send the whole carb back to RB and let them examine the carb for defects.

Thanks for any insight.

-Derek

Rx7carl

The surge/jerk is cause theyre opening too early. Thats the downside of mechanical secondaries. You cant mash the throttle. Also, the reason you dont feel the secs open with the vacuum setup is cause you shouldnt. They should open seamlessly and not noticeably. With a 650, they shouldnt open much at all as that carb is too big for your engine. I doubt that the carb is messed up. RB will only look at it I bet. Find someone with a flowbench and have them test it. I can watch vacuum secs open and close and modulate all day on my flowbench. Piece of cake.

Spinner-D(eluxe)

Well if you read the entire thread you would read that I have a 600cfm Holley, which is the correct size for my engine (according to RB). I bought it in a kit specifically for my 6-port 13B.

I know why there is a surge with the mechinacal setup, thats why I want to get the secondaries opening under vacuum (for a smooth transition from 2 to 4 barrels).

My question is what all else is there to check if I already tried different springs, running with a restriction bering and without? What other things could cause a weak vacuum signal on the secondaries diaphram/actuator???

Crit

iTrader: (6)

Hey, not to be a *****, but Carl HAS read the whole thread, as he's been posting throughout. I have two pretty heavily ported 4-port 13Bs and neither flows enough to need the Holley 600s that were on them. They just don't. I've moved to a 51IDA Weber and putting together a 48DHLA, simply because the Holley is too big to be effective. There's nothing else you can do, other than going to mechanical secondaries. You can rig up something like guys do on the Nikki, where the secondaries open half-way through the throttle travel, but move twice as fast so all four are full-open when the pedal's down. I've never really checked out how difficult it would be for the Holley.

Crit

iTrader: (6)

Come to think of it, you're right... a Holley is perfect. In fact, you could fab up a manifold pretty easily to allow a Holley to feed each rotor. I'll sell you either of mine. Seriously though, the Holley can't be beat for support, as the 4160s are sized for everything from a mild 350 to a truck 454, but really..... do you flow as much as a 350 at 6000 revs? Check Holley's website - the 350 is the smallest of the recommended engines to put under a 4160.