Holley 4160 on a '91 Nautique

[2Valve]

I rebuilt a Holley 4160 carburetor (Ford 351) for a buddy yesterday and solved a flooding issue on startup. But I'm not understanding the fast idle cam or choke settings with the electric choke.

 

Right now, the choke plate is completely closed on a cold engine and opens slowly as it's running. I would assume that's normal as the voltage to the choke heats up the spring inside, and slowly opening the plate.

 

Questions:

1. Does the choke plate need a specific gap with the cold engine or is that determined simply by the ability to start when cold?

2. What is the procedure to set the choke on the fast idle cam (part of the choke housing? On carbureted cars, you would press the pedal to the floor and start the engine seeing a higher idle and then after running a bit, press the throttle again to return to normal idle. Before starting would you push the throttle all the way forward, return to neutral and then start?

4. Once set on the fast idle, what's the normal rpm? I'm guessing about 1300-1500?

5. How would you return to normal idle and get the throttle off the fast idle cam?

6. I have the idle mixture screws set at 1 turn out. Is this within the accepted range? The motor is ultra smooth at that setting, seeing about 850 rpm in neutral.

 

Appreciate any insight.

2Valve

 

 

[Rednucleus]

I don't ever recall a ski boat having a cold fast idle setting that needed to be kicked down. Always have seen them started and rpm's increased manually in neutral as needed.

[2Valve]

@Rednucleus

I appreciate the info. I’m recalling that marine carbs don’t have a fast idle cam.

[jhughes]

At the end of the day a choke isn't really needed on a ski boat. Lots of folks just max them out and unplug them to effectively disable them. Two pumps on the throttle and it should start even with no choke.

[Orlando76]

Sounds like you’re on the right track. I’d like to see idle lower. If engine sounds happy with current mixture settings I’d keep it. I always like to put fresh plugs in once I feel carb is set and adjusted. Then pull plugs after a few hours run time. Plugs tell a lot. As jhughes mentioned choke isn’t necessary but I’d keep it. Two pumps on cold crank is all any properly tuned carby needs to crank.

[Jordan]

Go to one of the Mastercraft threads on fb. Peter Biever is the carb expert over there. He can answer your questions.

 

https://www.facebook.com/peter.biever.31

[jmhjgh]

I agree with Jordan. Get in contact with Peter either on Facebook or Teamtalk. My understanding is that the choke mechanism should not have a fast idle cam, unless someone has added it or you have a street carb on your boat.

[ReallyGottaSki]

I concur, no fast idle mechanism. If it did, its likely not the correct carb.

 

The turns suggest a bit lean, but the proof is in how it runs.

we've been getting best results setting the idle mix while in gear, but take precautions. Helps with minimizing change in rpm in and out of gear,as well as no lean stutter off-idle.

 

Am i misreading the idle hangs high sometimes?

 

 

[KRoundy]

I’d suggest you browse over to www.correctcraftfan.com

[2Valve]

Thanks everyone. I just confirmed that a cold start in the lake had zero issues. Choke plate closed, started without pumping the throttle and settled into a nice steady idle, with the choke plate slowly opening. We'll leave things as they are for now until something goes sour. Pretty happy with the results since the carb was flooding before when applying any throttle. We confirmed that the accelerator pump was squirting fuel but the flow was continuous. Now we get a nice even specific amount of fuel. Carb's work very well if you take the time to get 'em right.

[ALPJr]

You could try calling Discount Inboard Marine aka SkiDim.com. I bought a 4160 from them a few years ago and they were very helpful with remove and replace guidance. It was pretty much plug and play.

[Wayne]

Have a lot of experience working on Holley carbs. My opinionated recommendations:

1) The choke flap should be all the way closed for a cold start. Keep in mind the high idle cam interacts with the linkage and can hold the choke partially open.

2) The bi-metal spring in the choke housing pulls the high idle cam into position but you need to move the throttle open so the cam can drop into place and then move the throttle back to idle/neural for the choke and high idle mechanism to work the way it should.

3) you skipped 3 ?

4) high idle only needs to be as high as needed to keep the engine running on a cold start. I believe in an old holly tuning guide I have it said you should need the high idle more than 500 RPM above your warm idle.

5) As the choke mechanism warms up it drops the high idle cam but the throttle needs to be above the high idle cam so the cam can move and drop out of the way. So if you did a cold start and let the engine warm up you would need to move the throttle above the high idle just barely for the high idle cam to drop out of the way. Then you can lower the throttle to idle again and you will be off the high idle.

6) you should use a vacuum gauge to adjust the idle mixture screws. One turn out from all the way in is a good starting point. Idle screws are adjusted with a fully warm engine and on the base idle. Connect the vacuum gauge to manifold vacuum port, adjust one idle screw at a time while watching the vacuum gauge. The goal is to get the highest vacuum measurement possible, you may need to adjust the screw in or out.

[2Valve]

@Wayne Thank You very much for the detailed list. (I never liked the number 3) :)

 

I had my buddy pull me last night and the boat starts and runs almost as good as a port injected boat.

 

He's pretty happy and somehow I'm now considered a guru around the lake. lol!