Holley secondary speed screw

[AaronWhitt82]

Hey guys..... Once again it's that time to get the boat out of storage and do the whole de-winterization process and check everything over on the motor and get the ol Holley tuned up....
At the end of last year the carb started acting up on me once again. I believe it has something to do with the air/idle mixture screws and possibly the secondary speed screw.
I am finally going to invest in a vacuum gauge from my local JC Whitney so I can get the air/idle mixture screws set exactly where they need to be.
Here is the link for the vacuum gauge:
http://www.jcwhitney.com/vacuum-gaug.../p2008137.jcwx


Basically the boat was idling a bit high and I had the idle screw pretty much backed all the way off and it was still idling just around 900rpm's (not in gear)... This might have something to do with where the air/idle mixture screws were set because I just kind of guessed where to set them or maybe even the secondary speed screw...
Now this secondary speed screw is what confuses me... I'm not quite sure how to adjust it. I rebuilt the carb back in the Spring of 08 and I do not remember what I set this screw at....

Here is a link for the secondary speed screw:
http://www.youtube.com/watch?v=__3ruSX8Q_A

Also if I am understanding this correctly the idle screws need to be adjusted the same amount on the primary and secondaries so the throttle plates are opened the same amount???

After never working on a carb before in my life; I now pretty much know the Holley 4150 inside out, how to disassemble everything, rebuild it, adjust everything and how it all works. This is the only thing I am a bit confused about....

(All the info for my boat is in my sig)

Thanks

 

[zbnutcase]

Re: Holley secondary speed screw

That is NOT an idle speed screw on the secondary, it is just a stop screw to keep the throttle plates from sticking in the bores. To adjust back it off until the plates are fully closed, turn screw in until it touches lever then turn 1/4 turn more and your done.

 

[jtmarten]

Re: Holley secondary speed screw

The 2 idle/mixure screws on the primary metering plate should be set at 2-turns out to start. If your idle adjustment is set too high (primary plates are open) the idle circuit won't even be functioning at idle, so changing the idle/mixture screws will have no effect.

The link posted just took me to a page with multiple vids, nothing regarding a Holley setup, so I'm not sure what you're referring to as a speed screw.

 

[mkast]

Re: Holley secondary speed screw

rebuild it,

http://www.youtube.com/watch?v=__3ruSX8Q_A

Did you remove the throttle plates in the course of this rebuild?
If the idle screw is backed all the way out, and the engine still idles at 900 RPM, the throttle plates may not be seated. If this is the case, using a screwdriver, loosen the screws holding both primary throttle plates slightly, the spring on the throttle shaft will seat the plates, tighten the screws. If this works on the primaries, do the secondaries, the same condition may exist.

 

[AaronWhitt82]

Re: Holley secondary speed screw

The 2 idle/mixure screws on the primary metering plate should be set at 2-turns out to start. If your idle adjustment is set too high (primary plates are open) the idle circuit won't even be functioning at idle, so changing the idle/mixture screws will have no effect.

The link posted just took me to a page with multiple vids, nothing regarding a Holley setup, so I'm not sure what you're referring to as a speed screw.

Sorry about that link. For some reason I posted the wrong one. It is now fixed....
What I was trying to say is that I am buying a vacuum gauge so I can get my air idle/mix screws set correctly from the vacuum reading and then set the idle speed from there.
I also wasn't aware that if the idle adjustment is set too high that the idle circuit won't function. I just did some more reading about that and learned something new again. Pretty much anything more than 2 turns in of the idle speed screw and the idle circuit won't function....

http://www.youtube.com/watch?v=__3ruSX8Q_A

Did you remove the throttle plates in the course of this rebuild?
If the idle screw is backed all the way out, and the engine still idles at 900 RPM, the throttle plates may not be seated. If this is the case, using a screwdriver, loosen the screws holding both primary throttle plates slightly, the spring on the throttle shaft will seat the plates, tighten the screws. If this works on the primaries, do the secondaries, the same condition may exist.

I did NOT remove the throttle plates when I rebuilt the carb... I do remember checking the screws you are talking about and making sure they were tight before I put the carb back on. I will loosen them up and then see if the throttle plates seat and then tighten the screws back up. Never would have thought of checking this...

Thanks