Holley 670 Vacuum Secondary Issue ~ Opening late/not at all

[Chrysler]

Any ideas here will be greatly appreciated, I have a Holley 670 cfm 4150 with vacuum secondaries. Trouble is the secondaries hardly open and when they do it is at higher rpms when I'm pretty much topped out.
The air passage is free, the diaphram is good and I've resorted changed the spring to the lightest spring and even compressed it further before installing it, there is no check ball as some others have that I've read about. What I've found different is there is a brass restriction pressed into the housing and am temped to remove it. What do you the experts here think?
Engine is a 1965 361, mostly stock with Edelbrock intake and headers. Thanks!! Andrew

 

[commando1]

Watch the video all the way to end and then we'll discuss.
It may be working fine.

 

[Chrysler]

Wow, thanks! I had no idea Holley had videos. I've searched all over and didn't see this. It might explain my stumble off the line I've been experiencing, I'll report back later. Thanks again.

 

[commando1]

Glad I could help. Really!

 

[bajajoaquin]

If adjusting the secondaries doesnt fix the stumble off the line, check your vacuum hoses. Im pretty sure thats whats causing mine.

 

[commando1]

Secondaries, working properly or not will have little to do with stumble off the line.
It will require, on a Holley, a different accelerator cam (they come in different shapes) and after that, a different power valve.
There's an excellent Holley book out there. It's my Holley bible.

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[Chrysler]

Yep, heavier spring did it. What a difference! My thinking was totally backwards.

Stumble seems better. Definitely not vacuum leak thanks though. I tried a different accelerator cam on the weekend too which yeilded limited results. I used the white one. Quick fuel makes a kit with a range different cams. Power valve, will look into that, I just had it out too.

I have that book also but I have reading and comprehension troubles so it takes a little while to get through it.

 

[commando1]

That's great news. Good job to you for asking the right questions...
BTW, I had a real hard time with that Holley book.
I had to leave it by the toilet and take it small doses to understand WTH they were talking about.
Severe ADD

 

[68blackbird]

There are some really good Holley vids on Youtube....I knew nothing about them, watched the vids a few times, got to where I could set them up pretty good. They have different ones for jetting, acc pumps/cams, secondaries, ect..and the part where they say use a paper clip to see if sec are opening, you can also use a small wire tie that is lightly tightened.

https://www.youtube.com/watch?v=4xOiJQj6CSU

 

[commando1]

I get the best advice from YouTube many times.

Found out a way to literally pop off the rear brake drum on tapered axles with a $20 tool and a hammer.

 

[Chrysler]

I replaced the accelerator pump diaphragm and listed to what the talking carburetor had to say in that video, got the pump adjusted and no more stumble. Running the timing at 12 degrees, and I'm about to replace the fuel pump, the old one is having issues, the engine starts to surge and the hesitation starts to come back. All the issues I've had serves me right for buying a used Holley haha.

 

[commando1]

Extremely glad you got that stumble out. They can be very frustrating.