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I bought this boat last year. I was never able to get a really healthy idle until 900 RPM. I know it should be happy purring along at 600 RPM, the timing is spot on and all signs pointed to the carb. Visually, it was full of carbon deposits on the choke plate and just looked neglected.
I am hoping that these photos may help someone in the future, if only to provide a visual reference to what goes where. This is my first time rebuilding a four barrel, and I've only rebuilt motorcycle carbs before this. I am learning as I go here.
This is my carb, Holley 4160 list 50419.
As I understand it, the number under the list details when the carb was built. The 297th day of 1986 in this case. I'm not entirely sure if that's true or an old wives tale.
Holley's site provides a great reference for figuring out which kit you need. For my carb they spec'd the 703-29 rebuild kit. Amazon had the best price for me, $36 with free 2-day Prime shipping.
Anyone with a pre-1992 4160 should also consider ordering Holley part 125-500: Power Valve Check Ball Kit. This kit updates the old 4160s to include backfire protection - no more losing your power valve if your engine suffers a backfire. $14 on Amazon. Thank you thatsmrmastercraft!
Suggestion, take a ton of pictures of the small assemblies as you take them apart. This is the choke assembly.
One thing to clean is the choke breather screen. This provides some fresh air to the electric choke and keeps it from overheating. The screen on mine was completely full of carbon and I could not even blow through it. Take it out, soak it in carb cleaner and get it transparent again. A blocked breather will kill your choke.
The bowls were pretty clean.
After removing some of the easy things, I gave the body a long dunk in my $70 Harbor Freight ultrasonic cleaner. I turned it every few minutes and after the initial hour or so I'll drain the dirty solution and rinse the parts with water.
Later, before assembly I'll run them through and rinse them again.
I have found this cleaner to be much more effective than the carb cleaner soaks I used to give my dirty carb parts.
This thing works wonders, and I use it all the time with motorcycle parts. My solution is 1 part Simple Green and 3 parts water. Turn it on and watch the carbon deposits break up and float away.
That solution was pretty much clear when I started.
The cleaner has a heater, and helps soften up the old gasket material.
At this point, I was pretty certain of at least one problem that was causing my rough low idle. A major vacuum leak -- the primate throttle plates were not snapping fully closed. They would close with some assistance, but they were binding due to "gunk".
The plates would seal up nicely with a little assistance, but they should completely close off without additional assistance (I mean, the return spring should be enough to do the job).
By using a zip-tie, you can get the plate assemblies to stay open while they soak. Deposits have probably built up where they make contact with the throats.
Soaking the body and cleaning the throats did not fully solve the problem, so I knew I would have to remove the primate throttle plates and remove the bore to clean out any deposits that could be causing the friction which was preventing a full close.
These brass screws had to come out in order to remove the plates (so I could slide the shaft out and clean the bores).
Of course, one of the 4 brass screws snapped off. What I wish I knew then, was that the brass screws are "staked" in place which means the ends are mushroomed out to prevent them from ever working themselves lose and finding their way into your cylinders. Of course, this makes them difficult to remove if you did not know this in the first place!
Holley provides a great instruction document here for removing and replacing your throttle blades, should anyone encounter this in the future: http://www.holley.com/data/Products/...99R9978rev.pdf. I wish I would've found that before I snapped the screw, as it calls for filing off the far end of the screw before attempting to unscrew it. Oh well!
With some careful drilling and the help of an 8-32 tap, I got the old screw out of there and cleaned up the threads. I found a pack of new brass screws on eBay and now I just have to wait for them to arrive.
In the meantime, I took the shaft to my polisher and shined up the bearing surfaces on the shaft. I also took a bore brush from my gun cleaning kit and ran it through the throttle body to get any remaining deposits out of there. The assembly snaps shut now.
Now... the wait for parts to arrive. To be continued!
I am hoping that these photos may help someone in the future, if only to provide a visual reference to what goes where. This is my first time rebuilding a four barrel, and I've only rebuilt motorcycle carbs before this. I am learning as I go here.
This is my carb, Holley 4160 list 50419.
As I understand it, the number under the list details when the carb was built. The 297th day of 1986 in this case. I'm not entirely sure if that's true or an old wives tale.
Holley's site provides a great reference for figuring out which kit you need. For my carb they spec'd the 703-29 rebuild kit. Amazon had the best price for me, $36 with free 2-day Prime shipping.
Anyone with a pre-1992 4160 should also consider ordering Holley part 125-500: Power Valve Check Ball Kit. This kit updates the old 4160s to include backfire protection - no more losing your power valve if your engine suffers a backfire. $14 on Amazon. Thank you thatsmrmastercraft!
Suggestion, take a ton of pictures of the small assemblies as you take them apart. This is the choke assembly.
One thing to clean is the choke breather screen. This provides some fresh air to the electric choke and keeps it from overheating. The screen on mine was completely full of carbon and I could not even blow through it. Take it out, soak it in carb cleaner and get it transparent again. A blocked breather will kill your choke.
The bowls were pretty clean.
After removing some of the easy things, I gave the body a long dunk in my $70 Harbor Freight ultrasonic cleaner. I turned it every few minutes and after the initial hour or so I'll drain the dirty solution and rinse the parts with water.
Later, before assembly I'll run them through and rinse them again.
I have found this cleaner to be much more effective than the carb cleaner soaks I used to give my dirty carb parts.
This thing works wonders, and I use it all the time with motorcycle parts. My solution is 1 part Simple Green and 3 parts water. Turn it on and watch the carbon deposits break up and float away.
That solution was pretty much clear when I started.
The cleaner has a heater, and helps soften up the old gasket material.
At this point, I was pretty certain of at least one problem that was causing my rough low idle. A major vacuum leak -- the primate throttle plates were not snapping fully closed. They would close with some assistance, but they were binding due to "gunk".
The plates would seal up nicely with a little assistance, but they should completely close off without additional assistance (I mean, the return spring should be enough to do the job).
By using a zip-tie, you can get the plate assemblies to stay open while they soak. Deposits have probably built up where they make contact with the throats.
Soaking the body and cleaning the throats did not fully solve the problem, so I knew I would have to remove the primate throttle plates and remove the bore to clean out any deposits that could be causing the friction which was preventing a full close.
These brass screws had to come out in order to remove the plates (so I could slide the shaft out and clean the bores).
Of course, one of the 4 brass screws snapped off. What I wish I knew then, was that the brass screws are "staked" in place which means the ends are mushroomed out to prevent them from ever working themselves lose and finding their way into your cylinders. Of course, this makes them difficult to remove if you did not know this in the first place!
Holley provides a great instruction document here for removing and replacing your throttle blades, should anyone encounter this in the future: http://www.holley.com/data/Products/...99R9978rev.pdf. I wish I would've found that before I snapped the screw, as it calls for filing off the far end of the screw before attempting to unscrew it. Oh well!
With some careful drilling and the help of an 8-32 tap, I got the old screw out of there and cleaned up the threads. I found a pack of new brass screws on eBay and now I just have to wait for them to arrive.
In the meantime, I took the shaft to my polisher and shined up the bearing surfaces on the shaft. I also took a bore brush from my gun cleaning kit and ran it through the throttle body to get any remaining deposits out of there. The assembly snaps shut now.
Now... the wait for parts to arrive. To be continued!
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