Heya guys, So I've been throwing around the idea of changing one more final time. I have a holley 470 truck avenger carb in my garage that I rebuilt and used once on my truck but took off because the secondaries never seemed to open but I did love the snappiness of the throttle it was all there but the issue with the secondaries had me lost. Lately ive been on the search for maybe different metering blocks but no one has replacement ones because the secondary metering block is non adjustable.

Do you guys have any suggestions on what I could check? or maybe buy new metering block and make it so the secondary is non adjustable

 

How do you know the secondaries never opened.
They will only open when driving the under load not free revving the engine where you can see them.
See pages 11 and 12 in the manual below.

199r10268-4.pdf (holley.com)

 

Did the whole paperclip test after driving stayed in the same spot that my brother in law and I put it.

 

Have you tried using a softer spring on the diaphragm?
Is the vacuum passage from the diaphragm chamber to the intake manifold open?

 

Definitely determine whether the vacuum passage into the diaphram unit is getting vacuum, as Pmuller said.

Quick Fuel makes an adjustable secondary diaphram for Holley carbs. It costs about $30 on ebay. There is a youtube vid that will show you how to remove the old and install the new. It's really easy-peazy. On the QF unit is a simple screw--turn it one way to slow the secondaries from opening; turn the other way and they will open sooner. Set the screw in the oe position they recommend, and start doing driving tests, opening the screw a quarter of a turn each time, until you're happy with how the secondaries open. DON'T try to open the screw (counter-clockwise) more than a quarter of a turn at a time.

My Holley had no adjustment in the secondary side because it had a plate instead of a metering block. I bought a metering block, new longer filler tube and seals, and longer float bowl bolts, with the re-useable nylon washers/seals, from ... I believe it was Allstate carburetor, but I'm sure Summit has them too. Now I can change the jets in the secondary side as I wish. I opted for the m.block w/o a power valve.

 

F250 how are you doing?

I'm way ahead of you I have that vaccum diaphragm I dont believe I ever used it but it's on the carburetor right now but I think I'm gonna rebuild it again because it's been sitting for a couple years now

 

Hey there, Fordboy! I'm good. Truck is still going strong. I put in a zf5, and love it.
With that diaphram, I'd pull it and test it with a vacuum pump. If it works, don't fix it, ha ha. You'll get it working fine. Start the engine with the diaphram off, and put your finger on the vacuum hole, or a v. gauge.

 

Heya FordBoy.
What RPMs did you get up to? A 470 should definitely be opening up the secondaries if you're getting on it. They'd open up on my 600cfm.
Was it a used or new carb? As others said, it might just have way too strong of spring in it (if used).
Or maybe a blocked vacuum passage. Have you sprayed cleaner through them to be sure the passages are clear?

A secondaries metering block would only allow you to adjust the jetting, but not when they open and close. That's from the diaphragm and spring. And yeah, that QF adjustable housing is pretty nice.
However, I don't think it'll help much if you have a super heavy spring in it as it only adjusts based on the current spring. Maybe get a spring kit for when you rebuild it to be sure it has the right one?