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AaronWhitt82
04-22-2010, 02:36 AM
So 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/fuel pump tester 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-gauge-and-fuel-pump-tester/p2008137.jcwx

Here is a link of how to set the air/idle mixture screws:
http://www.youtube.com/watch?v=UPGLUsW5ZeE

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&playnext_from=TL&videos=olEnKChVnLM


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....

Thanks

kaneboats
04-22-2010, 10:13 AM
Larry, can you help?

mmandley
04-22-2010, 10:29 AM
I used to run Carbs on all my 77-79 Trans Ams i restored. As it says unless you have a huge ass cam you don't need the secondaries opened very much. It says if you have a big cam and the primary is not allowing the engine to idle very well you need to then balance the amount of idle fuel between the primary and secondary.

If you have adjusted the secondary already or by mistake then try to get it back to as close to being closed as possible. Not quite closed but also not very open.

I don't see you having a big loping cam in your boat that requires the secondary to be open very much.

Now you can simply adjust the primary once again to get the desired idle RPM you want.

AaronWhitt82
04-23-2010, 03:30 AM
I used to run Carbs on all my 77-79 Trans Ams i restored. As it says unless you have a huge ass cam you don't need the secondaries opened very much. It says if you have a big cam and the primary is not allowing the engine to idle very well you need to then balance the amount of idle fuel between the primary and secondary.

If you have adjusted the secondary already or by mistake then try to get it back to as close to being closed as possible. Not quite closed but also not very open.

I don't see you having a big loping cam in your boat that requires the secondary to be open very much.

Now you can simply adjust the primary once again to get the desired idle RPM you want.

Thanks alot for the reply. Exactly the answer I was looking for. The only bad part about adjusting this screw is that I have to take the carb off to adjust it. Like I said I can't remember what I adjusted it at when I rebuilt the carb.
I also posted this on Iboat's forum and some of the guys over there recommended the same setting as well... They said just about a quarter of a turn and your good to go.
Someone else also suggested that maybe the throttle plates aren't fully seating and to loosen the little screws on the plates and that the spring should pull them back and fully seat them and then you can tighten the screws. This is something I will be checking as well...
Also another suggestion was to check the throttle play and that it might be out of adjustment and not letting the throttle plates close all the way...

Also FYI for everyone else... Something else I learned today that if your idle adjustment is set too high (primary plates are open) the idle circuit won't even be functioning at idle.

mmandley
04-23-2010, 10:03 AM
Thanks alot for the reply. Exactly the answer I was looking for. The only bad part about adjusting this screw is that I have to take the carb off to adjust it. Like I said I can't remember what I adjusted it at when I rebuilt the carb.
I also posted this on Iboat's forum and some of the guys over there recommended the same setting as well... They said just about a quarter of a turn and your good to go.
Someone else also suggested that maybe the throttle plates aren't fully seating and to loosen the little screws on the plates and that the spring should pull them back and fully seat them and then you can tighten the screws. This is something I will be checking as well...
Also another suggestion was to check the throttle play and that it might be out of adjustment and not letting the throttle plates close all the way...

Also FYI for everyone else... Something else I learned today that if your idle adjustment is set too high (primary plates are open) the idle circuit won't even be functioning at idle.

All these are very good ideas, but don't over think or go silly adjusting and checking everything. Take 1 thing at a time. Adjust what you know is wrong, the screws. Then if this doesn't work go to the next most likely thing. Make a list and note all the changes as you do them. This will give you a track record of everything you did. This can come in handy if you need to go back and redo something.

AaronWhitt82
04-23-2010, 05:16 PM
All these are very good ideas, but don't over think or go silly adjusting and checking everything. Take 1 thing at a time. Adjust what you know is wrong, the screws. Then if this doesn't work go to the next most likely thing. Make a list and note all the changes as you do them. This will give you a track record of everything you did. This can come in handy if you need to go back and redo something.

That's how I usually adjust the carb is to do 1 thing at a time and go from there or anything else I am working on. I always make sure to write everything down for any adjustments or changes I make to anything and if I forget I can go back and look. (Apparently I forgot to write down what I set the secondary speed screw at because I didn't think it was a big deal...)
I keep saying it would be nice to have fuel injection, but I enjoy working on the carb and playing around with it to get the boat to run perfect. Always learn something new from it !!!

AaronWhitt82
04-23-2010, 05:20 PM
We've had some really good discussions about carb adjustment in the past.

So good, it turned me from a disbeliever to actually going out and drilling the caps and removing them to get to the adjustment screws.

One member "Wolf-", posted some great info and had a home page devoted to it.

I believe "Engine Nut" once posted the procedure for adjusting the carb by ear.

Well worth doing a search thru posts written by these two guys.

If Danny from Oklahoma happens to be reading this, I believe I included a copy of the adjustment procedure in the paperwork that came with your boat. Maybe he can post it here.

Ed - Thanks for this info. I will do a search and see if I can find what I'm looking for...
I'm hoping now that after messing with this carb on and off since I bought the boat that I can finally get this darn thing tuned in perfect once I buy the vacuum gauge and do some other adjustments !!!!