car won't idle & getting best vacuum with mixtures almost closed

Yeah it smells very rich.... I just realized it has so much play this morning. This is most likely the culprit huh? How do I fix it?

 

Simply bend the rod to the point that it's keeping the rear throttle shaft from rotating while engine vacuum is present. What rear secondary spring are you running? Another quick troubleshooting test would be to install the stiffer black spring to help overcome the tendency for engine vacuum to force any unwanted rotation of the rear throttle shaft.

 

I did that and there's still that much slack... I'll try bending the rod

 

If you have a black spring in there already and that extra tension pushing the rear plates closed didn;t help the situation?.. then you have other problems going on here.

Also keep in mind that timing plays a large role in idle quality(and where the screws need to be for attaining best vacuum) and emissions. Whats' the base timing set at?

And what's the total vac number?

 

Right now it's 22 initial and 42 total. But there's stil a lot of slack in the secondaries so I assume that is my problem still correct??

 

The secondary spring should not affect the idle. Even the lightest spring should not have them opening at idle. Make sure the set-screw on the bottom is backed off enough for the secondary throttle blade to close all the way. If they are still sloppy or open, you have a problem with the secondary linkage.

 

Yeah I actually checked all that this morning... There's still slack

 

Well of course the secondary springs don't affect idle any more than jet sizes. But.. they do in fact keep the engine from sucking through the secondaries under heavy idle vacuum. The lightest springs will in fact allow this to happen which is precisely why I told you to troubleshoot it with the heaviest one. Process of elimination without the need to bend things up, is all.

My quick guess is that you have the rear plates set incorrectly which is then causing you to misadjust the front side. Get the rear wrong and you'll never get the front where they belong. Then you'll have idle mixture screw misadjustments following that scenario too.

And FYI to avoid further confusion here. Almost every.. might just be EVERY Holley vac sec carb I've ever seen has some slop in the secondary linkage when the primary shafts are against the idle stop screw. Otherwise we'd all be bending linkages every time we put a big cam and turned up the idle speed. With that in mind it's pretty simple to see that the secondary spring is what actually keeps the secondaries closed and seated. Not the primary sides return spring tension.

 

Thank you groberts. That all makes sense to me now. But one thing I don't get... Isn't the rod going from the primaries into the secondaries meant to stop the secondaries from opening at idle?

 

i understand that after you crack the throttle the spring takes over but that link has a fairly large gap and not stopping the secondaries until its way too late

 

This is what I'm thinking too.

 

Man this takes me back. I used to make good money on Holley set ups and rebuilds. The secondary opening was my biggest money maker. It will cause exactly what your experiencing. Its overlooked a lot and misdiagnosed. That secondary blade should be adjusted so that it is just off the fully closed position. Fully closed may cause blades to bind in bore. Make sure the throttle shaft is not binding. Common issue. Also the return spring on the shaft is good. May be getting weak.

 

okay awesome ill definitely check those! thank you!