Place the on 57 312, g heads, 57 dist. and intake . Trying to tune it. Had some electrical issues that I believe have got sorted out now trying to tune. Issues I believe is with the vacuum secondary not opening. I am running a three speed with OD. Is that a issue? Have watched many Holley videos. They suggest that vacuum secondary carbs. are more for AT ?
Videos show you could by a small supply store of parts to tune. Nozzles, plastic cams, vacuum secondary springs. So figure I would ask as I am not knowing where to start.
Hopefully you all have not got tired of my problems.
Starts fine, idles good, just seem to not open secondary. Going to try the paper clip trick tomorrow. Seem to pull good but more like a 2 barrel.
Looking for direction. Maybe some one could tell what they are using for plastic cam color, squirter nozzle size, and vacuum secondary spring color.
Again hope I am note wearing my welcome out and you all give me the boot. I believe you all and this sight a great for us that are challenged.

I am running a similar Holley carb on my 292 (Holley 465).  My 292 has 312 heads, intake and distributor. My car has a stock T86 3 speed with O/D and a 4.11 rear gear.  My carb is not modified, it's just as it came out of the box.  It runs great.  My secondaries open when I stick my foot in it.  They should open no matter what transmission you have.  You can not get the secondaries to open by free revving the engine.  The secondaries open by vacuum. Are you sure they are not opening?   There are others on this forum who can help you tune your carb.  Your O/D is not the issue.

When the vacuum secondaries are operating properly, the transition when opening will be smooth without any noticeable bog or jerking in the acceleration.  If you have a leak at the secondary vacuum chamber, then the secondaries will not open as designed.  Here’s a past post showing how to bench test the Holley 4150/4160 4V carbs to insure that the secondaries are able to open.
http://forums.y-blocksforever.com/FindPost61185.aspx

Lorena, Texas (South of Waco)

today I tried the paper clip trick. Three times clip keep falling off.  will try the vacuum test ted mention,  can this be done on the carb mounted, or does it have to be taken off?  Going to help son for a while to get mind off of this for now.  Almost to point off looking for a different carb as I am so outside of knowledge base I am at wits end, and have no source here to turn to.  But will press on after a break.

The instructions with the carb go over the secondary tuning procedure.  If you currently do not feel the secondaries open, put in the softer spring.  If you still do not feel them open, then there is probably a problem with secondary actuation.  If you do feel them open with the light spring, go back to the medium spring and as long as you can't feel it with the medium spring, it should be good.  If you still feel it with the medium spring, go to the heavy spring.
There is a spring kit from Holley that allows you to get it dialed in even better.

You really need to learn how to do it because any carb can give you problems and just changing to another is an expensive way to go about "fixing" a problem, a problem that may not even exist in this case, and can introduce other problems.
Youtube is a great source of info.  All kinds of how to videos.


Lawrenceville, GA

Holley's are great carburetors.  I've had them on every classic car I have ever owned.  If you keep them maintained and use premium gaskets, they don't leak and they perform.  Don't give up and spend a lot of money on something that won't work nearly as well.  They're worth fixing right.

I have a 390 CFM on my 312, I can feel the secondary's open but they open slowly and you really need to focus on it, only problem with vac secondary's and manual transmission is the secondary's are pulled closed mechanically every time you lift your foot off the accelerator to shift (unless you power shift, not recommended with column shift).

They then have to start the opening cycle again. Not a problem for me as I drive like a grandpa, oh wait, I am LOL

First off THANK YOU ALL for you support and info. It did me good to walk away and see grand daughter and reset my brain. Thanks again as it helped.
Got the paper clip trick to work, secondary’s are working. Check timing and adjusted ( marks are hard to read ). But have a mark I use fo reference from. Seem to have improved but have kind of slow or sluggish pull to power. Going to try the reddish #2 hole in pump cam first, then maybe get the spring kit for vacuum secondary. It has a #31 nozzle but will try the other stuff first before looking at that.
Hopefully will not become stupid again while working through this. Great Forum with great people.

Ordinarily, you would swap nozzles, first.  However, on my 570, the #1 hole in the stock, orange cam did not touch the accelerator pump lever so there was some delay from the idle position before the pump activated.  Moving it to the #2 hole took care of that.

Before changing the position, take a look at down the carburetor and make sure fuel squirts from the nozzle the instant you move the throttle.  If it does not, take a look at the accelerator pump adjustment and make sure the cam is contacting the lever in the idle position.

Sluggishness can also be related to the mains but probably only if that is off by an extreme amount.  Depending on your engine combo, it could be.  The 570 is intended for near stock applications.  A bigger cam can throw it off quite a bit.


Lawrenceville, GA

Great information. Don’t know much about internals of the 312 I have but believe it is pretty much stock. I will look at what you suggested. And see what I finds. If the change to the #2 placement on plastic cam recheck the pump adjustment. If no improvement should I look at nozzle change ( go up or down ) or should I look at spring change on vacuum pump? Thanks