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Holley 4160 Idle Mixture Adjustment |
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NautiqueJeff 
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Joined: October-24-2003 Location: Lake Norman Status: Offline Points: 233 |
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 Topic: Holley 4160 Idle Mixture AdjustmentPosted: April-12-2017 at 11:51pm |
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Ok, hopefully this is a simple question, and you guys can point me in the right direction.
I just had PCM rebuild my carb on my '98 Ski Nautique. I dropped it in the water the other day and could barely get it to start. Reid and I played around with the idle mixture screws a little bit and got it started, but it still isn't set just right. I want to set the mixture just right, so I went out and grabbed a vacuum gauge and was planning to connect it and set the screws to the optimum settings using the vacuum readings. One problem -- my carb doesn't seem to have a vacuum port. Is this typical of a 75009 PCM Holley 4160? Here's where I was expecting the port to be. Am I looking in the wrong place? 
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Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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NautiqueJeff
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Joined: October-24-2003 Location: Lake Norman Status: Offline Points: 233 |
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Posted: April-13-2017 at 12:10am |
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My carb is a little different than the one above though. Here's a picture of a 75009 4160. As you can see, the bowls are slightly different (no sight plug, etc.), and there is no full manifold vacuum port at the base, and no timed spark vacuum port either (not that that would help me anyway).
If there is no vacuum port, do I just fall back to adjusting the idle mixture based solely on the RPM? 
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Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: April-13-2017 at 12:39am |
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Jeff first you need to get your mechanic off of the Blue Chair Rum Cream
 I took this off the internet- Idle Mixture Adjustment. Start vehicle, and let it warm up. Connect a vacuum gauge to an full time vacuum source (intake manifold). The carburetor throttle plate is just fine. (Very bottom part of the carb) With the vehicle running, (and in gear with an automatic) Turn the idle mixture screws on the metering block clockwise the same amount until you get your highest vacuum reading. Start with about 1/4 turn at time, and KEEP BOTH SIDES THE SAME! If, on rare occasion, the vacuum reading goes down when the screws go in, by all means turn them out 1/4 turn at a time until the highest vacuum reading is achieved. Don't forget to re-set the curb idle speed when you are done with the idle mixture. So you need to connect to manifold vacuum,either removing a plug in it and using an adapter or possibly connecting to the adapter for the pcv valve somehow, Good luck |
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NautiqueJeff
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Joined: October-24-2003 Location: Lake Norman Status: Offline Points: 233 |
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Posted: April-13-2017 at 12:56am |
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The only port this carb seems to have is this one. I tried connecting to that, just to see what I would get for a reading, and I got zero.
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Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: April-13-2017 at 1:39am |
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That is before the venturi's of the carb you need to be after. The easiest would be to tap into the black hose on this picture with a T to fit it and your gauge hose. Not the same engine but very close to what you'll have. I would get another hose and put the T into it,change them out when your done.
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NautiqueJeff
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Joined: October-24-2003 Location: Lake Norman Status: Offline Points: 233 |
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Posted: April-13-2017 at 2:00am |
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That's the info I needed! Thanks!
I'll tap into that and have a go at it. 
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Current Boats: 1998 Ski Nautique, 2000 Sport Nautique, 1985 Sea Nautique 2700 (twin-engine), 1981 Fish Nautique (twin-engine), 1980 Fish Nautique (twin-engine)
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ViperSammy
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Joined: August-13-2019 Location: Georgia Status: Offline Points: 31 |
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Posted: August-14-2019 at 10:04pm |
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Sorry to revive and old thread...
This looks like my carb, and I don't see any vacuum ports either. I need to adjust my idles as well. There is a small port to the left of the choke, it looks like it should have something attached, but I can't figure out what. Any ideas? I took the "cap" off of it, and there was a washer in it... Thanks! Scott |
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'85 Ski Nautique
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 10643 |
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Posted: August-14-2019 at 10:18pm |
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The small port to the left of the choke has a very small flow thru it to provide cooler air to the choke element housing to prevent the element from overheating itself. It's a built in small vacuum leak by design
Not a good spot to hook a vacuum gauge. Either tee it into the PCV hose or pull the PCV hose from the PCV valve and stick the vacuum gauge in the end of the hose with whatever adapters you need to prevent an unwanted vacuum leak. See Gary S's post 2 above yours for the PCV hose. |
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