New Holley wont stay running / idle

[Rockboyz]

Morning gents,
Yesterday I installed a new Holley 750 Vacuum secondary, manual choke on my 340. Out of the box, fired right up, idled, ran it down the street, pulled a few hole shots, and came back. Let the car run in the driveway for about 10 min, everything seemed perfect. car ran great. Shut it off, went in the house for about 20 min, came back out to start it again, now it wont idle without throttling it. Kind of "waves" up and down for about 10 seconds or so, then eventually dies. Thoughts? Many thanks in advance guys!

[73chalngr]

 :perfect10:is fuel line touching something and heating up creating a vapor lock at shut down

[Rockboyz]

I checked that, nothing was really moved. I did add a new piece of rubber fuel line, buts its in the same place.

[Cuda Cody]

Could it be an vacuum leak?  Have you checked to see if the carb has come loose on the base after it was heat cycled?   

[RUNCHARGER]

Yes: It sounds like a vacuum line or plug fell off.

[Rockboyz]

Checked all the lines, everything seemed to be fine. Decided to run it this morning. Fired up and idled fine. Gonna do the same thing I did yesterday and see if it acts up again. Thanks for the responses guys! Ill keep you posted!

[Strawdawg]

If it happens again, check the gas level in the float bowls to see if it is low, or high...

[Rockboyz]

Well, same results. Ran it down the street, seemed okay although at a stop sign in gear it didn't want to hold the idle so to speak. Full throttle, does well. brought it home, parked it for 20 min, again started it, wont stay running. As of right now its seems like it does this when its hot,

[Cuda Cody]

Was the car running and driving okay before the new carb?  What carb were you using?

[71-440]

Are you using a spacer between the carb and manifold?

[Chryco Psycho]

Have you gone through the basic tuning steps ?
There is a guide I wrote in the archives , you need to do a basic tuning set up right out of the box .
We can help you tune it further but need more info on what has been done so far

[Rockboyz]

I am using a spacer. I haven't touched any of the settings. Took it out of the box and put it on.
This new 750 replaced an old 780. The base plate on the 780 was wore

[Brads70]

I am using a spacer. I haven't touched any of the settings. Took it out of the box and put it on.
This new 750 replaced an old 780. The base plate on the 780 was wore

I assume you set the float levels and adjusted the idle mixture? Be sure to check that the throttle blades are not hanging up on the spacer and/or gaskets. Also check the linkages ( especially the secondary ) to make sure it's not contacting the intake and hanging up.

[gzig5]

Mine was acting that way when the front float was not adjusted correctly and it was running out of fuel in the front bowl.  It would run OK, but then wouldn't start.

[Chryco Psycho]

You are lucky it runs as well as it does , nothing runs well right out of the box , you have to do the basic settings , , it may be too rich & running well when cold but not once the heat comes up