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Holley Carburetor Experts - Rich After Rebuild?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Topic: Holley Carburetor Experts - Rich After Rebuild?
    Posted: April-17-2015 at 9:50am
To those who are not familiar with my Rat Rod Ski Tique project: The motor is 351w taken from a '83 Nautique 2001. The boat was "winterized" by the previous owner then totaled by a storm damaged tree 4+ years ago. Last summer I purchased the boat for parts & stole the motor to swap into my '79 Ski Tique. After removing the motor / electrical system from the Nautique I stand tested the motor with no tune up or modifications and it seemed to work fine. It had good compression, good oil pressure, started easily and idled fine so I changed the plugs, oil/filter, belts, re-tested it and winterized for the season.

Fast forward to this spring: I de-winterized the motor, put in fresh gas and took the boat to the lake. The motor ran fine with the exception of fuel dripping from the boosters after shutdown and it had a little residue on the transom. Unfortunately my 4160 does not have external float adjustments so I would have to get in there to check the float levels. Since I needed the gaskets anyway I went ahead and ordered the Holley 703-33 refresh kit and decided to just clean & rebuild the whole thing while it was out.

Although I have a pretty solid mechanical background, rebuilding everything from motorcycle engines to automatic transmissions this was my first jaunt with an automotive / marine carburetor.

The rebuild went pretty well. I disassembled, cleaned, & rebuilt the carb using the PCM service manual and the limited instructions included in the kit. Since I can't adjust the floats externally I set them parallel with the bowl in the inverted position to start.

For my 1st test I wanted to fill the bowls so I pulled the coil wire & cranked it over a few times. This yielded 5 leaks; both ends of the fuel line tube (that connects the 2 bowls), the fuel inlet flare fitting & the 2 bowls themselves. I pulled the carb and inspected the fuel line o-rings (which were the new ones) and they both had tears in them. I swapped them for the originals & re-torqued the bowls.

For my 2nd test I placed the carb on the intake & hooked up the fuel line. I didn't bother tightening it to the manifold as I expected it to leak somewhere else. I cranked it over a few times and was pleasantly surprised to find no external leaks. I specify external because I did notice a small amount of fuel leaking out between the carb and base gasket. I dismissed it and figured it was just because I hadn't tightened the carb to the intake manifold.

For my 3rd attempt. I secured the carb to the intake, hooked up the coil wire & attempted to fire up the motor. It didn't take long before the motor was up and running. It seemed to be running a bit rich so I closed up the idle mixture screws and got it to run a little bit better. With no 4bbl tuning experience I couldn't really quantify my results with anything more then basic carb knowledge. I tried following the tuning instructions to find the rich / lean limits and set the screw in the middle, but didn't notice much a difference while adjusting the screws. Instead I reverted back to my general understanding of carburetors; if it loaded up at idle it needed to be leaned out. If the throttle response was poor it was starving for fuel and needed to be richened up a bit. After 15-20 min of screwing around with it I got it to run with the idle screws between 1/2 - 3/4 turn open and you have to start it at WOT.   I'd like the idle to be a little bit lower and I could probably stand to tighten the alternator belt, but it runs pretty good IMO. Motor Test - Post Carb Rebuild

Only problem is it still smells rich & the transom has sooty residue on it like this: (more so on the port side then starboard)



I had to put the boat away before it started raining, but that didn't stop me from thinking about it all night. It's running rich, there's no arguing that and my gut says it's high fuel pressure / high float level. Although unlikely I'm leaning more towards the high fuel pressure as it had similar symptoms; running a bit rich w/ exhaust residue & internal carb leakage before the rebuild.

What's your take on it?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 10:21am
1. Take a look down the throat and see if you're dripping from the boosters at idle and/or after shut down. Plenty of bad (new) needle/seats these days.

2. Did you get the proper rebuild kit? Calling the Holley tech line with the list # is the only way I know of to be sure, there are a lot of 600cfm marine 4160's, I wouldn't rule out an improper gasket blocking an important fuel or air passage.

3. Make sure your idle mixture screws are responsive. Start the engine and put them all the way in. If the engine stays running then it's not running on the idle circuit. Either a wrong gasket or a passage is blocked.

4. If all of the above look good then start with the idle mixture screws 1.5 turns out, then get your rpm close (700ish). To get them dialed in perfectly requires a load (in gear, in the water). You want to adjust for max vacuum and set to 650rpm while in gear.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 10:42am
I have some answers:

1.) No fuel dripping from boosters after shut-down.

2.) As far as I know I did. My list number of 9392 was stated on the Holley site for the 703-33 rebuild kit, I compared gaskets before installing.

3.) IIRC it will die if I screw them in all the way. It will also load up and die if I back them out in the 1 1/2 - 2 turn area. I will check again this afternoon.

4.) I plan on a lake test tomorrow anyway so I will bring the specs & re-test in the water.


Followup Questions:

What do you mean by adjusting for max vacuum?

I saw in Holley 4160 Float Setting Thread that setting the floats 7/16 high worked. How does this compare to setting them parallel?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote backfoot100 Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 10:53am
When it's running, look down the throat and see if the boosters are leaking or even after you shut down. I'm guessing the float level is too high and pouring gas down the carb flooding it and causing your rich condition. The other option is too much fuel pressure will definitely keep the needle/seats open causing the same scenario but I didn't see anywhere that you put a new fuel pump in. Too much pressure might be an issue if it's a new fuel pump but an OEM pump shouldn't be a problem.

Several here (myself included) have found the standard Holley practice of the parallel float adjustment to be too high for our boats due to the engine angle (and even with my angled spacer). Readjust the float and yes, Holley marine carbs don't have an external float adjustment so deal with it. You want external float adjustment buy a quality aftermarket carb like a Quickfuel and you can have external float adjustments.

The idle mixture is generally 1 to 1 1/2 turns out and both should be the same. Your 3/4 turn is way too lean but if the boosters are dripping will definitely mess up your adjustments.



When people run down to the lake to see what's making that noise, you've succeeded.



Eddie
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 10:58am
I have never used float height as a tuning tool. If you're not dumping gas (too high) or running dry (too low) then I wouldn't mess with it. They don't have any effect on how fuel is metered beyond that.

You want to adjust your idle screws such that the engine pulls max vacuum at idle. This is how you determine that the a/f mix is optimal. It requires a vacuum gauge plumbed to manifold vacuum (like the port on the carb spacer where the Pcv is plumbed).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phatsat67 Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 11:05am
Vacuum gauge and in gear pushing the trailer. Adjust the carburetor to about 400-500 rpms in gear pushing the trailer then adjust idle mixture screws for maximum vacuum on the gauge.

EDIT: Something is leaking fuel for sure if you have to use WOT to get it to start. Open it WOT while its running then kill it with the key and see if anything is leaking from any of the auxiliary circuits or the baseplate itself.

When it is at WOT you can open the secondaries manually with your finger to look down and inspect there.

You rarely see any noticeable suit residue on boats that have proper mixture.

If you aren't comfortable going WOT and killing it you could disconnect the throttle cable and slowly push the accelerator pump down until it uses all the available fuel in it then go WOT with the throttle shaft while you are holding the accelerator pump down. The bog with lack of accelerator pump should kill the engine.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 1:36pm
So taking all that into consideration here's the plan:

- Pick up a vac/press gauge
- Pull the carb
    - Pull bowls
       - Check / raise floats
       - Check all internal hardware torque's
       - Check power valve torque
    - Reinstall & re-torque bowls
    - Reset idle screws to 1.5 turns
    - Crank boat & test fuel pressure (5-7.5 psi according to Holley)
- Reinstall carb
    - Torque to intake manifold
    - Test fire (in driveway)
    - Once running; look for both internal & external leaks
- Take to lake (Provided all is well in the driveway)
    - Water test (on trailer)
        - Vac gauge plumbed to intake
        - In gear
            - Adjust idle to 400 - 600 rpm
            - Adjust idle screws for max vacuum on gauge
            - Reset idle as needed


Questions:
1.) Any idea what I should be expecting for max vacuum?

2.) Is there any specific procedure to adjust the idle screws, do you alternate side to side adjusting them 1/8 of a turn at a time?

3.) Is there much (if any) of delay between adjusting the screws and the vacuum gauge changing?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mountain Man Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 2:24pm
You should expect >16 - 18 inches /Hg on the vacuum gauge. If less than 16 look for a leak. You can do one side at the time - after you get both sides close to the ideal (max vacuum) setting, reset your idle speed and then go back and re-verify both sides using the vacuum gauge again, only minor adjustments are expected at this point. There is very little delay in the time required to observe a change in the vacuum settings and you will also hear a change in the way engine runs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 6:35pm
Alright, So... I pulled the carb and tested the fuel pressure 7psi (good). I then pulled the bowls & noticed the power valve gasket looked to be mis-seated so I fixed that. I also adjusted the floats to sit a bit lower. I then reassembled the carb, adjusted the needles to 1 1/2 turns & installed the carb on the motor. It fired up and idled perfectly down to 500 RPM in the driveway, however its dripping fuel from the primary boosters while running & after shutdown and it's also leaking from the bowl inlet fitting to the carb & the inlet fitting to the flare.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Smithfamily Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 9:18pm
Ouch. Well you are making progress, and a learnin!
Js
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-17-2015 at 9:22pm
Holy sheet I think it works.

I figured my best shot a fixing the booster tube leak would be to adjust the front bowl float so I pulled the bowl and moved the float down even further. Next was to fix the bowl inlet fitting leaks. I tossed the nylon washer that was between the bowl and the fitting & replaced it with a black / copper crush washer from the carb kit. It was a sloppy fit on the fitting itself, but sat nicely on the face of the carb bowl. (plus I was running out of options) I then oiled the threads of the flare fitting & smoked it into the inlet fitting. No more leaks

Once the bowls are primed the motor fires almost immediately. I was able to get the idle down to 600 rpm and take stable readings on the vac gauge. Once adjusted the gas smell dissipated and the exhaust was much cleaner. The boosters also did not leak after the float adjustment. I wont celebrate anything until I've got it water adjusted & put a few hours on it, but it's the closest I've been yet.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-18-2015 at 11:18am
The lake test was bittersweet this morning. The boat fired up great, idled at 500 rpm. Before I could get to the vac test / adjustment I wanted to take a trip down the lake to warm it up. I stopped at the other end of the lake to adjust the idle when I found milky oil puked all over the engine bay. (from the unplugged pcv valve)

See the story: Mikly Oil 351w
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Post Options Post Options   Thanks (0) Thanks(0)   Quote phatsat67 Quote  Post ReplyReply Direct Link To This Post Posted: April-18-2015 at 11:22am
Oh no
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeftFieldEngineering Quote  Post ReplyReply Direct Link To This Post Posted: April-18-2015 at 12:04pm
Yea, tell me about it.
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