Holley Secondaries Aren't Opening

[eagleone1983]

I don't know why I've never checked this before but I did the paperclip test on my Holley 770 Street Avenger and the secondaries aren't opening. I'm actually happy they aren't because I've always felt that there should be more power to this car with all the add ons I have on the engine. So now I know where the power is hiding since I'm basically running a 2-barrel. I've done some googling and saw some things to check but I'm a carb dummy and don't know where the vaccum lines are that actuate the secondaries to verify they are clear of obstructions but here is what I've done so far...

- Verified the secondaires open manually when the primaries are held open, check. There is also a sort of sucking sound coming from the carb when I do this and when I let go of the secondaries they close slowly

-Verified the throttle cable adjustment is opening fully, check and double check

-Carb initially had a plain spring in it so I changed to a yellow spring (not the short one) still no worky

So that's what I've done so far and now some info about the engine/car. '69 Roadrunner Auto, 383 bored .030 over, cam is comp cams XE275HL .525 lift, duration @ .50" 231/237, 440 Source heads, roller rockers, edelbrock performer RPM Intake manifold, Schumaker headers

 

[Azure]

If they aren't opening while you drive you may have a ruptured secondary diaphragm. They won't open just revving the engine, you have to drive the car and put the engine under load.

 

[krowbar]

If they aren't opening while you drive you may have a ruptured secondary diaphragm. They won't open just revving the engine, you have to drive the car and put the engine under load.

X2

 

[eagleone1983]

Yeah I know they have to be under load that's why I said I used to paperclip trick to tell they aren't opening. So a ruptured diaphram would be the rubber gasket I'm guessing. Where do I plug the vaccum hole so I can open the secondaries manually plug that hole and verify the secondaries stay open until I let go of the vaccum hole. By doing that it should verify whether the diaphram is ruptured or not correct?

 

[krowbar]

It's an internal diaphragm. Don't think you can test it like that. Prob have to. take it apart and visually inspect the diaphragm

 

[Garys1969RR]

Take the sec opening diaphragm off. Hold the diaphragm against the spring. While covering the little vac hole with your thumb, release spring pressure and the dia. should stay where it is until you remove your thumb. Then it should return to closed position. That's how I check the dia for leaks.

 

[eagleone1983]

Thanks Gary, I pulled the unit off and plugged the hole and it didn't move and actually wouldn't move if I pulled on the rod so it seals really well. The screws holding it on were pretty easy to remove like they weren't really tight so I'm hoping after I put another paper clip on it and drive that might have been my problem.

 

[Garys1969RR]

Ok now make sure you have the tiny 1/4 inch diam round cork gasket that goes between the diaphragm housing and carb. And there is a passage goes from that hole to the primary side of the carb near the boost venturi. You can see it if you look closely. As air rushes past there when you open the primary throttle blades, it creates a vacumn which opens the secondaries. And it is also connected to a small tube in the sec side near the venturi which helps the sec open all the way. Its a very simple system and works well when all the parts are sealed up and working properly.

 

[Meep-Meep]

A few things here. You may not get any secondary action because it's possible your engine doesn't need it at whatever RPM you ran it to. This would be the most obvious. Checking the secondary diaphragm as Gary suggested is good but I bet it's fine assuming the carb hasn't been messed with. You shouldn't get any secondary action revving in neutral in the driveway but I guess you already know that.

 

[eagleone1983]

Thanks for the update guys. Well I ran it last night but the paperclip fell off so it didn't do me a lot of good so I'll try again tonight. I did have the cork gasket installed and looked fine.

Meep, even with a light spring that I have in it you think it may not need to open? I figure with such a heavy car gunning it from a stop would at least open them a little bit. I'm not sure what RPM I was at because I don't have a tach installed yet but I gunned it from a stop to a little over 50mph.

 

[Meep-Meep]

I had a 735 Holley (OEM 428 Ford carb) on my 455 Olds powered jet boat and the secondaries never opened. The engine is exposed so I can watch what happens under a load and not the slightest bit of movement of the secondary throttle shaft. You might try a 600 CFM (1850) and see what the paper clip does. With my limited exposure to your problem it seems you have too much carb.

Here is another bit of info. One thing that is typically found on Holleys is a check ball in the vacuum diaphragm but I have no idea on the 770. I'm pretty sure this is to slow down the secondary opening by restricting the vacuum signal to the diaphragm. To see if you have this ball take the diaphragm unit off and take it apart and see if the ball is in the vacuum passage well. The location of the ball seems counter intuitive but if you look closely there is a tiny notch in the seat to allow for air flow.

 

[Garys1969RR]

You can always put a small screw or a tie in the sec linkage on the driver side of the carb. This will force the sec open each time you floor it. Did this on my sons 383, and then we could tell what it sounded like when they opened. Let the engine be at least 2000RPM when you try this. Prob get a big lag or Flat Spot before it really takes off. On the 383 they weren't opening we found out. So replaced the dia now they open. You can tell when they open even with the vac sec. Its about the last 1/4 of pedal travel.

 

[eagleone1983]

Maybe I'll try that out just to see what difference it makes when they open. Gary what are some of the specs of your son's 383? That'll help me determine whether or not Meep is right and maybe with the size of my carb my engine just doesn't require 4 barrels.

 

[Garys1969RR]

Maybe I'll try that out just to see what difference it makes when they open. Gary what are some of the specs of your son's 383? That'll help me determine whether or not Meep is right and maybe with the size of my carb my engine just doesn't require 4 barrels.

Ok he has a 383 in a 70 Super Bee, with dome distons, 915 heads, rebuilt with 1.74 ex valves but no porting. C/R is prob around 12 to 1. Holley Street Dominator intake, the carb is a 750 with vac secondaries. Stock HP ex manifolds, XE274HL cam which has .488/.491 lift. We are at 5200 feet where we live. I am sure your motor pulls enough air to open the secondaries. Do your pistons come to the top of the cyl bore? This one does, plus with the dome it has plenty of compression. You may want to install a new vacumn diaphragm along with the yellow SHORT spring, and a new cork seal at the carb body. This is what we did, and it started working good. You can also get a quick change top, where you can change the spring without removing the whole vac assembly.

 

[eagleone1983]

Thanks Gary, I've already got a quick change top. I've got KB400 pistons so they are flat top with valve reliefs. I can't remember how far in the hole they are but it's not much at all. My compression is at 9.7:1

 

[66blvee]

holley secondaries

Best way to find out if the secondaries are working is as follows.

Remove the clip that holds the secondary rod to the throttle shaft and slide the rod off.
Take an air hose and blow across the small hole located in the passenger side secondary throttle bore and watch the shaft coming from the secondary pod to see if it moves up. What you are accomplishing is a wide open throttle effect of air flow across the small hole that actuates the secondaries. You can do this on the engine (motor off) or on the work bench. See the picture I posted.

 

[eagleone1983]

Thanks 66! I took the car out, this time with a paperclip that wouldn't fall off. It did move about a 1/4 to 3/8 down the rod so I think they are working. I'm not sure if the clip should go all the way down or not but I was doing WOT runs from about 10 mph to 60 mph. Sure the heck gets there fast. You think I should put an even lighter spring than what I have in now?

 

[Garys1969RR]

I would go lighter until it bogs on sec opening, then go back 1 step heavier. I have a yellow short spring with 1 coil cut off, and it works great! Sometimes a slight bog when cold, but works fine when warmed up. You just have to experiment.

 

[eagleone1983]

Just wanted to finalize this thread. I ended up going all the way down to white and my secondaries are now opening all the way as evidenced by the paper clip. I also added a couple degrees of timing at the same time before test driving so I'm not sure what did it but I can no longer floor the throttle through a turn. I think I scared the crap out of the lady sitting in the left hand turn lane on the opposite side of me

 

[67 coronet]

Just wanted to finalize this thread. I ended up going all the way down to white and my secondaries are now opening all the way as evidenced by the paper clip. I also added a couple degrees of timing at the same time before test driving so I'm not sure what did it but I can no longer floor the throttle through a turn. I think I scared the crap out of the lady sitting in the left hand turn lane on the opposite side of me

scaring the stiffs is the best way to know your test was good.sounds like problem solved,nice.